2000

A. N. Akın, Z. İ. Önsan “CO hydrogenation by K-promoted coprecipitated Co/Al2O3” Reaction Kinetics and Catalysis Letters 70 (2) (2000) 275-280.(SCI).

 

Kurt N., Haliloglu T., “Conformational Dynamics of Chmotrypsin Inhibitor 2 in Free and Complex Forms”, Abstracts of Papers of American Chemical Society: ACS Polymeric Materials Science and Engineering, 83, 397 (2000).

 

Haliloglu, T., Bahar, I., Jernigan, R. L., “Collective dynamics of class I MHC/peptide complexes and binding to T cell receptors”, Biophysical Journal, 78, 34A (2000).

 

Jang J. J., Haliloglu T., von Meerwall E. D., and Mattice W. L., “Effect of Vinyl Content on Self-Diffusion in Polybutadiene Melts”, Macromolecules, 33, 4271-4277 (2000).

 

Baschnagel, J.; Binder, K.; Doruker, P.; Gusev, A. A.; Hahn, O.; Kremer, K.; Mattice, W. L.; Müller-Plathe, F.; Murat, M.; Paul, W.; Santos, S.; Suter, U. W.; Tries, V. (2000) "Bridging the Gap between Atomistic and Coarse-Grained Models of Polymers: Status and Perspectives" Advances in Polymer Science 152, 41-156.

 

Doruker, P.; Atilgan, A. R.; Bahar, I. (2000) "Dynamics of Proteins Predicted by Molecular Dynamics Simulations and Analytical Approaches: Application to alpha-Amylase Inhibitor" Proteins, 40, 512-524.

 

Ozisik, R.; Doruker, P.; Mattice, W. L.; von Meerwall, E. D. (2000) "Translational Diffusion In Monte Carlo Simulations of Polymer Melts: Center of Displacement vs. Integrated Autocorrelation Function" Computational and Theoretical Polymer Science 10, 411-418.

 

Vao-soongnern, V.; Doruker, P.; Mattice, W.L. (2000) "Simulation of an Amorphous Polyethylene Nanofiber on a High Coordination Lattice" Macromolecular Theory and Simulations, 9, 1-13.
Avcı, A.K., Çamurdan, M.C., Ülgen, K.Ö., “Quantitative description of protein adsorption by frontal analysis”, Process Biochemistry, 36 (2000) 141-148.


Avcı, A.K., Trimm, D.L., Önsan, Z.İ., “Simulation of alternative catalyst bed configurations in autothermal hydrogen production”, Studies in Surface Science and Catalysis, 130 (2000) 2753-2758.

 

Aksoylu, A. E., Freitas, M. M. A, Figueiredo, J. L., “Bimetallic Pt-Sn Catalysts Supported on Activated Carbon: I. The Effects of Support Modification and Impregnation Strategy”, Applied Catalysis A: General, 192 (2000) 29-42.

 

Karaselçuk, R., İşli, A. İ., Aksoylu, A. E., Önsan, Z. İ., “ CO Hydrogenation on Nickel-Vanadium Catalysts”, Applied Catalysis A: General, 192 (2000) 263-271.

 

Bülbül, T., İşli, A. İ., Aksoylu, A. E., Önsan, Z. İ., “Investigation of Alternative Support Materials for Monometallic and Bimetallic Catalysts of CO Hydrogenation”, Studies in Surface Science and Catalysis, 130 (2000) 3723-3728.

 

Serp, Ph., Hierso, J-C., Feurer, R., Corratge, R., Kihn, Y., Kalck, Ph., Aksoylu, A. E., Faria, J. L, Pacheco, A. M. T., Figueiredo, J. L., “Characterisation and Reactivity of Activated Carbon Supported Platinum Catalysts Prepared by Fluidised Bed Organometallic Chemical Vapour Deposition (FBOMCVD)”, Studies in Surface Science and Catalysis, 130 (2000) 1001-1006.

 

Aksoylu, A. E., Freitas, M. M. A, Figueiredo, J. L., “Bimetallic Pt-Sn Catalysts Supported on Activated Carbon: II. CO Oxidation”, Catalysis Today, 62 (2000) 337-346.

 

Köse O., U. Akman, Ö. Hortaçsu, “Semi-Batch Deterpenation of Origanum Oil by Dense Carbon Dioxide”, Journal of Supercritical Fluids, 18(1), 49-63 (2000)

 

Savaş S., Kırdar B.,Keats J. B.B.:Tecniques and technologies for detection of genomic abnormalities, Archive of Oncology 8(4), 171-176, 2000

 

Birol G., Önsan Z.İ., Kırdar B.:Studies on the fermentation of recombinant yeast cells: Stability and kinetics of biomass and protein production, Journal of Chemical Technology and Biotechnology 75,729-737,2000

 

Dork K.,Macek Jr M.,Mekus F.,Tümmler B.,Sakmaryova I., Krebsova A.,Vavrova V.,Zemkova D.,Macek Sr.M.,Koudova M.,Ginter E.,Petrova N. V., Ivaschenko T.,Baranov B.,Witt M.,Pogorzelski A.,Bal J.,Zekanowski C., Stuhrmann M.,Bauer I.,Thamm B.,Wagner K.,Nechiporenko M.,Livshits L., Komel R.,Vouk K.,Ravnic-Glavac M.,Kocheva S.,Efremov G.D.,Kucinkas V.,Teder M.,Krumina A.,Kusic J.,Radojkovic D.,Sangiuolo F.,Jordanova A., Sertic J.,Richter D.,Rukavina A.S.,Kadasi L., Malone G.,Cuppens H., Carles S.,Claustres M.,Verlingue C.,Ferec C., Bjorck E.,Strandvik B.,Onay T., Kırdar B., Cardoso H., Montgomery M., Nakielna B.,Hughes D.,Casals T.,Estivill X.,Aznarez I., Tzountzouris J.,Tsui L-C.,Zielenski J.: A novel 21-kilobase deletion,CFTRdele2,3(21kB),in the CFTR gene:a cystic fibrosis mutation of Slavic origin common in Central and East Europe, Human Genetics 106(3) , 259-268 , 2000

 

Savaş S.,Gökgöz N,Kayserili H,Ozkınay F.,Yüksel-Apak M.,Kırdar B. Screening of deletions in SMN,NAIP and BTF2p44 genes in Turkish muscular atrophy patients, Human Heredity 50 , 162-165 , 2000

 

B.Özbek, K. Ö. Ülgen (2000) “The Stability of Enzymes after Sonication”, Process Biochemistry, 35 (9), 1037-1043.

 

M.Düzenli, K. Ö. Ülgen (2000) ‘Optimisation of Mobile Phase Conditions for the Purification of TaqI endonuclease’, Chromatographia, 52 (6), 377-380.


 

Record 1 of 108
Author(s): Tezel A; Hortacsu A; Hortacsu O
Title: Multi-component models for seed and essential oil extractions
Source: JOURNAL OF SUPERCRITICAL FLUIDS 2000, Vol 19, Iss 1, pp 3-17
Publisher: ELSEVIER SCIENCE BV
Addresses: Hortacsu O, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: essential oils; modeling; multi-component extraction; seed oils; supercritical fluid extraction
KeywordsPlus: SUPERCRITICAL CARBON-DIOXIDE
Abstract: Various types of models have been presented for the SFE of seed and essential oils in the literature. Most of these models consider the natural matrix as a porous sphere and the extractable material as a single chemical specie. In this work, the shrinking-core model is modified for application to a multi-component system in order to simulate SFE of seed oil components. The porous sphere model with the desorption-dissolution-diffusion mechanism to express the extraction is also extended for application to a multi-component system to simulate the SFE of essential oils. The results of these more rigorous analyses suggest possibilities for selective extraction of the mixture constituents, if some processing parameters could be better controlled. Selective extraction would eliminate the need for additional separation operations, which would reduce the cost of production of the desired target component(s). (C) 2000 Elsevier Science B.V. All rights reserved.
Times Cited: 0
Source item page count: 15
Publication Date: NOV 15
IDS No.: 377PH
29-char source abbrev: J SUPERCRIT FLUID
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 2 of 108
Author(s): Akin AN; Onsan ZI
Title: CO hydrogenation by K-promoted coprecipitated Co/Al2O3
Source: REACTION KINETICS AND CATALYSIS LETTERS 2000, Vol 70, Iss 2, pp 275-280
Publisher: AKADEMIAI KIADO
Addresses: Onsan ZI, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Kocaeli Univ, Dept Chem Engn, Kocaeli, Turkey
Author Keywords: coprecipitation; Co/Al2O3; K-promotion
KeywordsPlus: CATALYSTS; OLEFINS
Abstract: Effect of K promotion on the CO hydrogenation activity and selectivity of coprecipitated Co/Al2O3, has been studied. K addition is found to lower total activity while enhancing C-2-C-4 olefins selectivity; kinetic data indicate that the reaction mechanism is not affected.
Times Cited: 0
Source item page count: 6
Publication Date: JUL
IDS No.: 367JZ
29-char source abbrev: REACT KINET CATAL LETT
Publisher address: PO BOX 245, H-1519 BUDAPEST, HUNGARY


Record 3 of 108
Author(s): Duzenli M; Ulgen KO
Title: Optimization of the mobile phase conditions for the purification of TaqI endonuclease
Source: CHROMATOGRAPHIA 2000, Vol 52, Iss 5-6, pp 377-380
Publisher: VIEWEG
Addresses: Ulgen KO, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Author Keywords: column liquid chromatography; ion exchange chromatography; TaqI endonuclease
Abstract: TaqI endonuclease was purified by high performance ion exchange liquid chromatography with linear gradient elution. Of the chromatographic media tested as mobile phases for the HPLC purification of TaqI endonuclease, sodium acetate (pH 5.0) and phosphate (pH 7.0) buffers were appropriate for use with ration exchange columns, and L-histidine (pH 6.0) and Tris (pH 8.0) buffers with anion exchange columns.
Times Cited: 0
Source item page count: 4
Publication Date: SEP
IDS No.: 360HP
29-char source abbrev: CHROMATOGRAPHIA
Publisher address: ABRAHAM-LINCOLN-STRABE 46, POSTFACH 15 47, D-65005 WIESBADEN, GERMANY


Record 4 of 108
Author(s): Avci AK; Camurdan MC; Ulgen KO
Title: Quantitative description of protein adsorption by frontal analysis
Source: PROCESS BIOCHEMISTRY 2000, Vol 36, Iss 1-2, pp 141-148
Publisher: ELSEVIER SCI LTD
Addresses: Ulgen KO, Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Author Keywords: frontal analysis; ion exchange chromatography; protein purification; mathematical model; parameter estimation; sensitivity analysis
KeywordsPlus: PERFORMANCE LIQUID-CHROMATOGRAPHY; BIOSPECIFIC ADSORPTION; AFFINITY-CHROMATOGRAPHY; AMINO-ACIDS; FINITE BATH; PARTICLES; EXCHANGERS; PEPTIDES; BEHAVIOR; COLUMNS
Abstract: Protein adsorption in packed columns was investigated theoretically and experimentally by frontal analysis and ion exchange chromatography. A dynamic model describing interfacial and intraparticle mass transfer and surface reaction phenomena was used in theoretical analysis. The effect of operating conditions, including temperature, feed concentration, column length and diameter, on the performance of breakthrough curves were determined. Two different techniques are employed in the estimation of the mass transfer parameters and the interaction rate constant. Use of model parameters obtained from finite bath studies results in the prediction of the 70% of the breakthrough profiles whereas simultaneous parameter estimation and solution of the partially differential model equations yield full prediction of the adsorption phenomenon. The former technique can be used in the design and scale-up of chromatography columns only if the later parts of protein adsorption are not of importance. (C) 2000 Elsevier Science Ltd. All rights reserved.
Times Cited: 0
Source item page count: 8
Publication Date: SEP
IDS No.: 355KX
29-char source abbrev: PROCESS BIOCHEM
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND


Record 5 of 108
Author(s): Kose O; Akman U; Hortacsu O
Title: Semi-batch deterpenation of origanum oil by dense carbon dioxide
Source: JOURNAL OF SUPERCRITICAL FLUIDS 2000, Vol 18, Iss 1, pp 49-63
Publisher: ELSEVIER SCIENCE BV
Addresses: Akman U, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Author Keywords: dense CO2 deterpenation; origanum oil; fractionation column; semi-batch; monoterpene
KeywordsPlus: SUPERCRITICAL-FLUID EXTRACTION; CITRUS OIL; FRACTIONATION; REMOVAL
Abstract: Semi-batch deterpenation of origanum oil (Origanum Munituflorum) by dense (sub/supercritical) CO2 was studied in an unpacked column with two temperature zones which were applied to column's upper and lower sections. Experimental results at combinations of 70 and 85 bar pressure and 38 and 55 degrees C temperature levels were reported. The results were discussed in terms of 14 major components, and the monoterpene (MT) and non-monoterpene (NMT) fractions of the oil. The oil was obtained from the top of the column at four different deterpenation time-cuts (integral samples of 0-15, 15-25, 25-35, and 35-45 min time intervals). In addition, the effects of the amount of oil feed charged to the extraction vessel, the solvent-to-oil ratio, and the presence of glass beads (0.5 cm) in the column as packing material were demonstrated. The best separation between the MTs and NMTs was achieved at 70 bar with 38 degrees C lower-section and 55 degrees C upper-section temperatures. At these conditions, the MTs are preferentially separated (with relative-distribution-ratio values greater than 2.0) from NMTs (with relative-distribution-ratio values less than 0.5), almost independent of the deterpenation time (flat maximum occurs in the 15-25 min deterpenation time-cut). It is concluded that any occurrence of single-phase state in the column deteriorates the effectiveness of the separation. Lower densities (higher temperatures) at the upper section of the column enhance the separation by causing internal reflux. Statistical analyses of the data and a response-surface analysis based on empirical models are presented. The suggested processing scheme that employs selective CO2 extraction and rectification has the potential to be used in essential-oil refining technology. (C) 2000 Elsevier Science B.V. All rights reserved.
Times Cited: 0
Source item page count: 15
Publication Date: AUG 10
IDS No.: 347UJ
29-char source abbrev: J SUPERCRIT FLUID
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 6 of 108
Author(s): Birol G; Onsan Z; Kirdar B
Title: Studies on fermentation with recombinant yeast cells: plasmid stability and kinetics of biomass and protein production
Source: JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY 2000, Vol 75, Iss 8, pp 729-737
Publisher: JOHN WILEY & SONS LTD
Addresses: Kirdar B, Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Author Keywords: recombinant yeast; Saccharomyces cerevisiae; kinetic models; plasmid stability
KeywordsPlus: SACCHAROMYCES-CEREVISIAE; ALPHA-AMYLASE; EXPRESSION; STRAINS; GROWTH; STARCH; CDNA; GENE
Abstract: Plasmid stability of the recombinant Saccharomyces cerevisiae YPB-G strain harbouring a YEp plasmid with alpha-amylase and glucoamylase genes as a fusion has been investigated in shake flasks and in a bioreactor using various compositions of media containing glucose or starch as the main carbon source. The medium composition affected both the growth characteristics and the stability of the plasmid. Superior plasmid stability was obtained in yeast minimal medium and in complex medium with glucose. Plasmid stability was substantially increased at high growth rates. Additional data were collected in the same system to investigate the kinetic characteristics of biomass and protein production, and unstructured kinetic models were used to interpret the results. At high initial glucose concentrations, where the biomass and protein production rates were similar, the kinetic models displayed good fits associated with high degrees of correlation. (C) 2000 Society of Chemical Industry.
Times Cited: 0
Source item page count: 9
Publication Date: AUG
IDS No.: 340EA
29-char source abbrev: J CHEM TECHNOL BIOTECHNOL
Publisher address: BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND


Record 7 of 108
Author(s): Ozbek B; Ulgen KO
Title: The stability of enzymes after sonication
Source: PROCESS BIOCHEMISTRY 2000, Vol 35, Iss 9, pp 1037-1043
Publisher: ELSEVIER SCI LTD
Addresses: Ozbek B, Yildiz Tech Univ, Dept Chem Engn, Sisli Campus, TR-80270 Istanbul, Turkey
Yildiz Tech Univ, Dept Chem Engn, TR-80270 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: enzyme stability; inactivation; acoustic cavitation; wave duty cycle
KeywordsPlus: ALCOHOL-DEHYDROGENASE; RELEASE KINETICS; CELL DISRUPTION; SHEAR
Abstract: The effects of operating conditions of sonication on the stability of some commercially purified enzyme preparations were investigated. Buffered solutions of six enzymes, alcohol dehydrogenase (ADH), malate dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G6PDH), L-lactic dehydrogenase (LDH), alkaline phosphatase (AP) and beta-galactosidase (beta G)were sonified over a range of power outputs up to 40 W. The enzymes had variable stabilities with complete stability for AP, and over 70% inactivation for G6PDH. Some inactivation models were tested for an understanding of the relation between sonification intensity and enzyme stability. Sonication processing times also affected the inactivation rate of ADH and MDH. The stability of sonified ADH was decreased with time when compared with unsonified controls. Increasing the viscosity of process fluid with glycerol gave 39% inactivation of ADH, while the control showed 15% inactivation for the operational conditions. The forces involved in the fluid must therefore have a significant role to play in the inactivation process. (C) 2000 Elsevier Science Ltd. All rights reserved.
Times Cited: 0
Source item page count: 7
Publication Date: MAY 9
IDS No.: 330DC
29-char source abbrev: PROCESS BIOCHEM
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND


Record 8 of 108
Author(s): Keskin O; Bahar I; Jernigan RL; Beutler JA; Shoemaker RH; Sausville EA; Covell DG
Title: Characterization of anticancer agents by their growth inhibitory activity and relationships to mechanism of action and structure
Source: ANTI-CANCER DRUG DESIGN 2000, Vol 15, Iss 2, pp 79-98
Publisher: OXFORD UNIV PRESS
Addresses: Covell DG, NCI, SAIC, Lab Expt & Computat Biol, Mol Struct Sect,NIH, Frederick, MD 21702 USA
NCI, SAIC, Lab Expt & Computat Biol, Mol Struct Sect,NIH, Frederick, MD 21702 USA
Bogazici Univ, TUBITAK Adv Polymer Mat Res Ctr, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, TUBITAK Adv Polymer Mat Res Ctr, Ctr Polymer Res, TR-80815 Bebek, Turkey
NCI, SAIC, DCTDC,DTP, Lab Drug Discovery Res & Dev, Frederick, MD 21702 USA
NCI, Div Canc Treatment & Diag, Dev Therapeut Program, NIH, Frederick, MD 21702 USA
Author Keywords: clustering behavior; SVD; tumor cell-line screen
KeywordsPlus: NATIONAL-CANCER-INSTITUTE; TUMOR-CELL-LINES; DRUG DISCOVERY; COMBINATORIAL LIBRARIES; ELLIPTICINE ANALOGS; SCREEN; INFORMATION; PATTERNS; IDENTIFICATION; INTERFACE
Abstract: An analysis of the growth inhibitory potency of 122 anticancer agents available from the National Cancer Institute anticancer drug screen is presented. Methods of singular value decomposition (SVD) were applied to determine the matrix of distances between all compounds. These SVD-derived dissimilarity distances were used to cluster compounds that exhibit similar tumor growth inhibitory activity patterns against 60 human cancer cell lines. Cluster analysis divides the 122 standard agents into 25 statistically distinct groups. The first eight groups include structurally diverse compounds with reactive functionalities that act as DNA-damaging agents while the remaining 17 groups include compounds that inhibit nucleic acid biosynthesis and mitosis. Examination of the average activity patterns across the 60 tumor cell lines reveals unique 'fingerprints' associated with each group. A diverse set of structural features are observed for compounds within these groups, with frequent occurrences of strong within-group structural similarities. Clustering of cell types by their response to the 122 anticancer agents divides the 60 cell types into 21 groups. The strongest within-panel groupings were found for the renal, leukemia and ovarian cell panels. These results contribute to the basis for comparisons between log(GI(50)) screening patterns of the 122 anticancer agents and additional tested compounds.
Times Cited: 0
Source item page count: 20
Publication Date: APR
IDS No.: 331HM
29-char source abbrev: ANTI-CANCER DRUG DES
Publisher address: GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND

Record 9 of 108
Author(s): Jang JH; Haliloglu T; von Meerwall ED; Mattice WL
Title: Effect of vinyl content on self-diffusion in polybutadiene melts
Source: MACROMOLECULES 2000, Vol 33, Iss 11, pp 4271-4277
Publisher: AMER CHEMICAL SOC
Addresses: von Meerwall ED, Univ Akron, Dept Polymer Sci, Akron, OH 44325 USA
Univ Akron, Dept Polymer Sci, Akron, OH 44325 USA
Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Univ Akron, Dept Phys, Akron, OH 44325 USA
Univ Akron, Maurice Morton Inst Polymer Sci, Akron, OH 44325 USA
KeywordsPlus: CONFIGURATIONAL STATISTICS; SEGMENTAL RELAXATION; POLYMER MELTS; CHAINS; MICROSTRUCTURE; DIMENSIONS; LATTICE; MODELS; BLENDS
Abstract: Diffusion coefficients, D, have been measured at five temperatures for melts of 14 samples of polybutadiene with varying vinyl content, f(v), covering a broad range. Seven of the samples have a molecular weight, M, near 1300, and the other seven have M near 3400. The experiments show that D tends to decrease with increasing f(v). This trend in the experiments can be rationalized by two seemingly different approaches. One successful approach utilizes free volume theory. The other successful approach is a Monte Carlo simulation that employs different jump rates for beads representing the two types of butadiene units. The two methods may not be as different as they appear initially, because they both incorporate, directly or indirectly, the fact that the glass transition temperature moves closer to the temperature used for measurement of D as f(v) increases.
Times Cited: 0
Source item page count: 7
Publication Date: MAY 30
IDS No.: 320AF
29-char source abbrev: MACROMOLECULES
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036 USA


Record 10 of 108
Author(s): Dork T; Macek M; Mekus F; Tummler B; Tzountzouris J; Casals T; Krebsova A; Koudova M; Sakmaryova I; Macek M; Vavrova V; Zemkova D; Ginter E; Petrova NV; Ivaschenko T; Baranov V; Witt M; Pogorzelski A; Bal J; Zekanowsky C; Wagner K; Stuhrmann M; Bauer I; Seydewitz HH; Neumann T; Jakubiczka S; Kraus C; Thamm B; Nechiporenko M; Livshits L; Mosse N; Tsukerman G; Kadasi L; Ravnik-Glavac M; Glavac D; Komel R; Vouk K; Kucinskas V; Krumina A; Teder M; Kocheva S; Efremov GD; Onay T; Kirdar B; Malone G; Schwarz M; Zhou ZQ; Friedman KJ; Carles S; Claustres M; Bozon D; Verlingue C; Ferec C; Tzetis M; Kanavakis E; Cuppens H; Bombieri C; Pignatti PF; Sangiuolo F; Jordanova A; Kusic J; Radojkovic D; Sertic J; Richter D; Rukavina AS; Bjorck E; Strandvik B; Cardoso H; Montgomery M; Nakielna B; Hughes D; Estivill X; Aznarez I; Tullis E; Tsui LC; Zielenski J
Title: Characterization of a novel 21-kb deletion, CFTRdele2,3(21 kb), in the CFTR gene: a cystic fibrosis mutation of Slavic origin common in Central and East Europe
Source: HUMAN GENETICS 2000, Vol 106, Iss 3, pp 259-268
Publisher: SPRINGER VERLAG
Addresses: Dork T, Hannover Med Sch, Inst Human Genet, D-30625 Hannover, Germany
Hannover Med Sch, Inst Human Genet, D-30625 Hannover, Germany
Hannover Med Sch, Dept Pediat Pulmonol, D-30625 Hannover, Germany
Charles Univ, Inst Biol & Med Genet, Prague, Czech Republic
Hosp Sick Children, Dept Genet & Genom Biol, Toronto, ON M5G 1X8, Canada
Hosp DYR, Genet Dept IRO, Barcelona, Spain
Russian Acad Sci, Med Genet Res Ctr, Moscow, Russia
Inst Obstet & Gynecol, St Petersburg, Russia
Polish Acad Sci, Inst Human Genet, PL-60479 Poznan, Poland
Inst TB & Lung Dis, Rabka, Poland
Natl Res Inst Mother & Child, Warsaw, Poland
Dept Human Genet, Graz, Austria
Dept Med Genet, Rostock, Germany
Childrens Hosp, Univ Clin, Freiburg, Germany
Univ Munster, Inst Human Genet, D-4400 Munster, Germany
Otto Von Guericke Univ, Inst Human Genet, Magdeburg, Germany
Univ Erlangen Nurnberg, Inst Human Genet, D-8520 Erlangen, Germany
Inst Human Genet, Leipzig, Germany
Ukrainian Acad Sci, Inst Mol Biol & Genet, UA-252627 Kiev, Ukraine
Inst Hereditary Disorders, Minsk, Byelarus
Comenius Univ, Inst Mol Physiol & Genet, Bratislava, Slovakia
Univ Ljubljana, Fac Med, Inst Pathol, Mol Genet Lab, Ljubljana, Slovenia
Med Ctr Mol Biol, Ljubljana, Slovenia
Univ Hosp Vilnuis, Ctr Human Genet, Vilnius, Lithuania
Med Acad, Dept Med Biol & Genet, Riga, Latvia
Univ Tartu, Ctr Med Genet, EE-50090 Tartu, Estonia
Macedonian Acad Sci & Arts, Skopje, Macedonia
Bogazici Univ, Dept Chem Engn & Med Biol & Genet, Bebek, Turkey
Royal Manchester Childrens Hosp, Manchester M27 1HA, Lancs, England
Univ N Carolina, Dept Pathol & Lab Med, Chapel Hill, NC USA
Ctr Hosp Univ, Montpellier, France
Hop Debrousse, Lyon, France
Ctr Transfus Consanguine, Brest, France
Univ Athens, Dept Pediat 1, Athens, Greece
Catholic Univ Louvain, Ctr Human Genet, B-3000 Louvain, Belgium
Univ Verona, DMIBG, Sect Biol & Genet, I-37100 Verona, Italy
Tor Vergata Univ, Catedra Genet Umana, Rome, Italy
CSS Mendel, Rome, Italy
Univ Hosp Obstet & Gynecol, Lab Mol Pathol, Sofia, Bulgaria
Inst Mol Genet & Genet Engn, Belgrade, Yugoslavia
Univ Sch Med, Clin Inst Lab Diag, Zagreb, Croatia
Sahlgrens Univ Hosp, E Gothenborg Univ, Dept Clin Genet & Pediat, S-41345 Gothenburg, Sweden
IIBCE, Montevideo, Uruguay
Alberta Childrens Prov Gen Hosp, Calgary, AB T2T 5C7, Canada
St Pauls Hosp, CF Adult Clin, Vancouver, BC V6Z 1Y6, Canada
IWK Grace Hlth Ctr, Halifax, NS, Canada
St Michaels Hosp, CF Adult Clin, Toronto, ON M5B 1W8, Canada
KeywordsPlus: TRANSMEMBRANE CONDUCTANCE REGULATOR; IDENTIFICATION; ALLELES; DNA; RECOMBINATION; HETEROGENEITY; POPULATION; 90-PERCENT; SEQUENCE; ABSENCE
Abstract: We report a large genomic deletion of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, viz.. a deletion that is frequently observed in Central and Eastern Europe. The mutation, termed CFTRdele2.3(21 kb), deletes 21,080 bp spanning introns 1-3 of the CFTR gene. Transcript analyses have revealed that this deletion results in the loss of exons 2 and 3 in epithelial CFTR mRNA, thereby producing a premature termination signal within exon 4. In order to develop a simple polymerase chain reaction assay for this allele, we defined the end-points of the deletion at the DNA sequence level. We next screened for this mutation in a representative set of European and European-derived populations. Some 197 CF patients, including seven homozygotes, bearing this mutation have been identified during the course of our study. Clinical evaluation of CFTRdele2.3(21 kb) homozygotes and a comparison of compound heterozygotes for Delta F508/CFTRdele2,3(21 kb) with pairwise-matched Delta F508 homozygotes indicate that this deletion represents a severe mutation associated with pancreatic insufficiency and early age at diagnosis. Current data show that the mutation is particularly common in Czech (6.4% of all CF chromosomes), Russian (5.2%), Belorussian (3.3%). Austrian (2.6%), German (1.5%), Polish (1.5%), Slovenian (1.5%), Ukrainian (1.2%), and Slovak patients (1.1%). It has also been found in Lithuania, Latvia, Macedonia and Greece and has sporadically been observed in Canada, USA, France, Spain, Turkey, and UK, but not in CF patients from Bulgaria, Croatia, Romania or Serbia. Haplotype analysis has identified the same extragenic CF-haplotype: XV-2c/KM. 19 "A" and the same infrequent intragenic microsatellite haplotype 16-33-13 (IVS8CA-IVS17bTA-IVSI7bCA) in all examined CFTRdele2,3(21 kb) chromosomes, suggesting a common origin for this deletion. We conclude that the 21-kb deletion is a frequent and severe CF mutation in populations of Eastern- and Western-Slavic descent.
Times Cited: 3
Source item page count: 10
Publication Date: MAR
IDS No.: 307PE
29-char source abbrev: HUM GENET
Publisher address: 175 FIFTH AVE, NEW YORK, NY 10010 USA


Record 11 of 108
Author(s): Cvetkovska M; Koseva S; Buzarovska A; Baysal BM; Yasar B; Karal-Yilmaz O; Popovic IG; Katsikas L
Title: ABA type block copolymers of poly(monobutyl itaconate) and poly(monocyclohexyl itaconate) with poly(dimethylsiloxane): Synthesis and characterization
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS 2000, Vol 201, Iss 6, pp 685-693
Publisher: WILEY-V C H VERLAG GMBH
Addresses: Baysal BM, TUBITAK Marmara Res Ctr, Dept Chem, TR-41470 Gebze Kocaeli, Turkey
TUBITAK Marmara Res Ctr, Dept Chem, TR-41470 Gebze Kocaeli, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Univ Belgrade, Fac Technol & Met, YU-11001 Belgrade, Yugoslavia
Sv Kiril & Metodij Univ, Fac Technol & Met, Skopje 91000, Macedonia
KeywordsPlus: PHYSICAL-PROPERTIES; ACID-ESTERS); ACID
Abstract: Monoesters of itaconic acid (monobutyl itaconate and monocyclohexyl itaconate) were synthesized and used as monomers. Poly(monobutyl itaconate) (PMBI) and poly(monocyclohexyl itaconate) (PMCHI) were prepared by free radical polymerization of these monomers using tert-butyl hydroperoxide as initiator. Subsequently, ABA type block copolymers where the A block is PMBI or PMCHI and the B block is poly(dimethyl siloxane) (PDMS) were synthesized by free radical polymerization using a macroinitiator (diperoxycarbamate) containing PDMS units. The structural formulae of the products were confirmed by spectral analysis. The molecular weights of the products are not high. Therefore the mechanical and physical properties are rather poor. However, porous structures of copolymers are observed by means of SEM.
Times Cited: 0
Source item page count: 9
Publication Date: APR 14
IDS No.: 306RB
29-char source abbrev: MACROMOL CHEM PHYSICS
Publisher address: MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY


Record 12 of 108
Author(s): Keskin O; Jernigan RL; Bahar I
Title: Proteins with similar architecture exhibit similar large-scale dynamic behavior
Source: BIOPHYSICAL JOURNAL 2000, Vol 78, Iss 4, pp 2093-2106
Publisher: BIOPHYSICAL SOCIETY
Addresses: Jernigan RL, NCI, Lab Expt & Computat Biol, Div Basic Sci, NIH,Mol Struct Sect, MSC 5677,Rm B-116,Bldg 12B, Bethesda, MD 20892 USA
NCI, Lab Expt & Computat Biol, Div Basic Sci, NIH,Mol Struct Sect, Bethesda, MD 20892 USA
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Polymer Res Ctr, TR-80815 Bebek, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, TR-80815 Bebek, Turkey
KeywordsPlus: BINDING-PROTEIN; ESCHERICHIA-COLI; VIBRATIONAL DYNAMICS; FOLDED PROTEINS; CLASSIFICATION; FLUCTUATIONS; CHEMOTAXIS; DATABASE; LEUCINE
Abstract: We have investigated the similarities and differences in the computed dynamic fluctuations exhibited by six members of a protein fold family with a coarse-grained Gaussian network model. Specifically, we consider the cofactor binding fragment of CysB; the lysine/arginine/ornithine-binding protein (LAO); the enzyme porphobilinogen deaminase (PBGD); the ribose-binding protein (RBP); the N-terminal lobe of ovotransferrin in ape-form (apo-OVOT); and the leucine/ isoleucine/valine-binding protein (LIVBP). All have domains that resemble a Rossmann fold, but there are also some significant differences. Results indicate that similar global dynamic behavior is preserved for the members of a fold family, and that differences usually occur in regions only where specific function is localized. The present work is a computational demonstration that the scaffold of a protein fold may be utilized for diverse purposes. LAO requires a bound ligand before it conforms to the large-scale fluctuation behavior of the three other members of the family, CysB, PBGD, and REP, ail of which contain a substrate (cofactor) at the active site cleft. The dynamics of the ligand-free enzymes LIVBP and apo-OVOT, on the other hand, concur with that of unliganded LAG. The present results suggest that it is possible to construct structure alignments based on dynamic fluctuation behavior.
Times Cited: 5
Source item page count: 14
Publication Date: APR
IDS No.: 302DE
29-char source abbrev: BIOPHYS J
Publisher address: 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA


Record 13 of 108
Author(s): Savas S; Gokgoz N; Kayserili H; Ozkinay F; Yuksel-Apak M; Kirdar B
Title: Screening of deletions in SMN, NAIP and BTF2p44 genes in Turkish spinal muscular atrophy patients
Source: HUMAN HEREDITY 2000, Vol 50, Iss 3, pp 162-165
Publisher: KARGER
Addresses: Kirdar B, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Genet & Mol Biol, TR-80815 Bebek, Istanbul, Turkey
Istanbul Med Sch, Inst Child Hlth, Istanbul, Turkey
Ege Univ, Fac Med, Dept Pediat, Div Genet & Teratol, Izmir, Turkey
Author Keywords: SMA; deletions; hybrid SMN gene; phenotype-genotype correlation
KeywordsPlus: MOTOR-NEURON GENE; DISEASE; PROTEIN; IDENTIFICATION; CONVERSION; SEVERITY; COMPLEX
Abstract: Deletions of the spinal muscular atrophy (SMA)-determining gene, SMN1, NAIP, and a third multicopy gene, BTF2p44tel were investigated in 60 unrelated Turkish SMA patients. SMN1 was deleted for at least exons 7 and 8 in 85% of the Turkish SMA patients. The NAIP gene was deleted in 75 and 33% of type I and type II SMA patients, respectively. Analysis of the 5'end of the BTF2p44tel gene indicated the extension of deletion in 13.3% of the cases, mainly in type I patients. Deletions of the NAIP and BTF2p44tel genes were detected in 1.3 and 3.9% of carrriers, respectively, in Turkish SMA families, Two patients were detected to harbor the hybrid SMN gene, one type II with deletion of the NAIP gene, and one type III without deletion of the NAIP gene. Copyright (C) 2000 S. Karger AG, Basel.
Times Cited: 0
Source item page count: 4
Publication Date: MAY-JUN
IDS No.: 289CB
29-char source abbrev: HUM HERED
Publisher address: ALLSCHWILERSTRASSE 10, CH-4009 BASEL, SWITZERLAND


Record 14 of 108
Author(s): Kraselcuk R; Isli AI; Aksoylu AE; Onsan ZI
Title: CO hydrogenation over bimetallic nickel-vanadium catalysts
Source: APPLIED CATALYSIS A-GENERAL 2000, Vol 192, Iss 2, pp 263-271
Publisher: ELSEVIER SCIENCE BV
Addresses: Onsan ZI, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Author Keywords: nickel-alumina; nickel-vanadium alumina; CO hydrogenation; kinetics
KeywordsPlus: NI-MO/AL2O3 CATALYSTS; SUPPORTED NICKEL; CARBON-MONOXIDE; KINETICS; COBALT; METHANATION; MOLYBDENUM; PROMOTERS; OXIDES; NI/AL2O3
Abstract: A series of gamma-Al2O3 supported Ni, Ni-V, Ni-V-K catalysts were prepared by impregnation or sequential impregnation to study the effects of V and K promotion on structural properties of Ni catalysts and their catalytic performance in CO hydrogenation. The Ni content of the samples was fixed at 5 wt.% while the V content was varied between 0.5 and 2 wt.%. Finally, 0.5 wt.% K was added to 5 wt.% Ni-1 wt.% V/Al2O3 for obtaining enhanced olefin selectivities, Experimental results indicate that total activity and C-2-C-4 hydrocarbons production are increased by V addition up to 1 wt.% while olefin selectivities show a decreasing trend in the same range. The addition of K decreases the total hydrocarbons production of the catalyst, more specifically the production of paraffinic hydrocarbons and CO2, resulting in an increase in the ratio of C-2-C-3 olefins to paraffins. The maximum selectivity for lower hydrocarbons is obtained at 548 K with the 5 wt.% Ni-l wt.% V-0.5 wt.% K catalyst. Regression analysis of intrinsic kinetic data obtained in the initial rate region on the Ni-V-K catalyst shows that CO consumption kinetics is best correlated by the surface carbide mechanism with irreversible dissociative adsorption of hydrogen as the rate-limiting step. (C) 2000 Elsevier Science B.V. All rights reserved.
Times Cited: 0
Source item page count: 9
Publication Date: FEB 14
IDS No.: 278FM
29-char source abbrev: APPL CATAL A-GEN
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 15 of 108
Author(s): Haliloglu T; Mattice WL
Title: Simulation of rotational isomeric state models for polypropylene melts on a high coordination lattice
Source: REVIEWS IN CHEMICAL ENGINEERING 1999, Vol 15, Iss 4, pp 293-305
Publisher: FREUND PUBLISHING HOUSE LTD
Addresses: Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Bogazici Univ, Ctr Polymer Res, Istanbul, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, TR-80815 Bebek, Istanbul, Turkey
Univ Akron, Inst Polymer Sci, Akron, OH 44325 USA
KeywordsPlus: CHAINS
Abstract: Recently the rotational isomeric state (RIS) model for unperturbed polymers has been combined with potential energy functions designed for the description of the interaction of pairs of molecules for the Monte Carlo simulation of coarse-grained representations of the chains on a high coordination lattice, under conditions where individual snapshots can be "reverse mapped" back to continuous space, with all atoms presented. This method, which was originally devised for RIS chains with interdependent bonds subject to symmetric potential energy functions, has been extensively applied to the conformation, energetics, structure, and dynamics of melts, free-standing thin films, and fibers, as well as the cohesion of two films of polyethylene (PE) chains. Later, the latter technique has been extended to handle vinyl polymers of desired stereochemistry and stereochemical sequence, with application to polypropylene (PP) chains. Here, a brief summary of previous simulations of the properties of PP chains will be made along with a general review of the simulation method.
Times Cited: 1
Source item page count: 13
IDS No.: 277FL
29-char source abbrev: REV CHEM ENG
Publisher address: STE 500, CHESHAM HOUSE, 150 REGENT ST, LONDON W1R 5FA, ENGLAND


Record 16 of 108
Author(s): Bahar I
Title: Dynamics of proteins and biomolecular complexes: Inferring functional motions from structure
Source: REVIEWS IN CHEMICAL ENGINEERING 1999, Vol 15, Iss 4, pp 319-347
Publisher: FREUND PUBLISHING HOUSE LTD
Addresses: Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Ctr Polymer Res, TR-80815 Bebek, Istanbul, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, TR-80815 Bebek, Istanbul, Turkey
KeywordsPlus: STATE HYDROGEN-EXCHANGE; TRANSFER RNA-SYNTHETASE; 3-DIMENSIONAL STRUCTURE; VIBRATIONAL DYNAMICS; MONOCLONAL-ANTIBODY; SINGLE-PARAMETER; FOLDED PROTEINS; 2-PROCESS MODEL; FOLDING UNITS; RESOLUTION
Abstract: A model referred to as a Gaussian network model (GNM) was recently introduced for estimating the dynamic characteristics of biomolecular structures, based on atomic coordinates in the native conformation. The model relies on the construction of a Kirchhoff matrix of contacts between sufficiently close interaction sites, the latter being conveniently chosen as the individual residues of the protein, or nucleotides of the nucleic acid. Knowledge of Kirchhoff matrix permits us to determine the fluctuation behavior in the neighborhood of the folded structure, a modal decomposition of which yields information on the cooperative modes of motion. Application of the GNM to several systems is presented. The model accurately predicts the X-ray crystallographic temperature factors and the Gibbs free energy changes associated with H/D exchange in solution near native state conditions. The utility of the GNM and related mode decomposition method for extracting information on the structural elements cooperatively involved in biological function is illustrated by application to an intact imunoglobulin G structure. Regions acting as hinges and the most flexible regions involved in antigen recognition are accurately identified, in close agreement with experimental observations.
Times Cited: 0
Source item page count: 29
IDS No.: 277FL
29-char source abbrev: REV CHEM ENG
Publisher address: STE 500, CHESHAM HOUSE, 150 REGENT ST, LONDON W1R 5FA, ENGLAND


Record 17 of 108
Author(s): Toksoy E; Ozdinler PH; Onsan ZI; Kirdar B
Title: High level secretion of TaqI restriction endonuclease by recombinant Escherichia coli
Source: BIOTECHNOLOGY TECHNIQUES 1999, Vol 13, Iss 11, pp 803-808
Publisher: KLUWER ACADEMIC PUBL
Addresses: Kirdar B, Bogazici Univ, Dept Chem Engn, PK 2, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: TaqI restriction endonuclease; MBP fusion protein; secretion; extracellular production
KeywordsPlus: BACTERIOCIN-RELEASE-PROTEIN; EXTRACELLULAR PRODUCTION; EXPRESSION; SYSTEM; STREPTOKINASE; EXCRETION
Abstract: The production and high level secretion of TaqI restriction endonuclease using bacterial secretion signal within the malE gene was achieved by cloning the PCR-amplified gene from Thermus aquaticus into E. coli. The maltose binding protein (MBP) part of the MBP-TaqI fusion protein expressed by this construct did not interfere with the biological activity of the TaqI restriction endonuclease. E. coli XL1 carrying pH185 produced 332 U ml(-1) TaqI endonuclease 81% of which was secreted into the medium without apparent cell lysis. Optimization of culture conditions and selection of the host strain were found to be important for the efficient extracellular production of this protein.
Times Cited: 0
Source item page count: 6
Publication Date: NOV
IDS No.: 272DY
29-char source abbrev: BIOTECHNOL TECHNIQUE
Publisher address: SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS


Record 18 of 108
Author(s): Kayaman N; Gurel EE; Baysal BM; Karasz FE
Title: Kinetics of coil-globule collapse in poly(methyl methacrylate) in dilute solutions below Theta temperatures
Source: MACROMOLECULES 1999, Vol 32, Iss 25, pp 8399-8403
Publisher: AMER CHEMICAL SOC
Addresses: Baysal BM, Tubitak Marmara Res Ctr, Dept Chem, TR-41470 Gebze, Kocaeli, Turkey
Tubitak Marmara Res Ctr, Dept Chem, TR-41470 Gebze, Kocaeli, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Univ Massachusetts, Dept Polymer Sci & Engn, Amherst, MA 01003 USA
KeywordsPlus: SINGLE-CHAIN COLLAPSE; TRANSITION; POLYSTYRENE; CYCLOHEXANE
Abstract: The time dependence of coil-globule collapse in atactic poly(methyl methacrylate) samples having molecular weights 6.5 x 10(6) and 3.3 x 10(6) g/mol dissolved in isoamyl acetate and n-butyl chloride were studied by dynamic light scattering. For example, a dilute solution of PMMA (6.5 x 10(6) g/mol) in isoamyl acetate was quenched from 61 degrees C (Theta temperature) to 18.5 degrees C. As a result, the measured hydrodynamic radius ([R-h]) was reduced from 42 +/- 2 to 15 +/- 2 nm. For the cells used in these DLS measurements the thermal equilibration time was found to be about 20 s. The transition from coil to globule in this cell was observed to take place in almost 35 s. We have found the coil-to-globule transition time to be inversely related to the depth of quench (Delta T) of the process. This transition time also increases with increase in molecular weight of the polymer chain.
Times Cited: 1
Source item page count: 5
Publication Date: DEC 14
IDS No.: 266ZC
29-char source abbrev: MACROMOLECULES
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036 USA


Record 19 of 108
Author(s): Aroguz AZ; Baysal BM
Title: Thermal, mechanical, and morphological characterization studies of poly(2,6-dimethyl-1,4-phenylene oxide) blends with polystyrene and brominated polystyrene
Source: JOURNAL OF APPLIED POLYMER SCIENCE 2000, Vol 75, Iss 2, pp 225-231
Publisher: JOHN WILEY & SONS INC
Addresses: Baysal BM, TUBITAK Marmara Res Ctr, Dept Chem, POB 21, TR-41470 Gebze, Turkey
TUBITAK Marmara Res Ctr, Dept Chem, TR-41470 Gebze, Turkey
Univ Istanbul, Fac Engn, Dept Chem, TR-34850 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-81700 Bebek, Turkey
Author Keywords: blends; poly(phenylene oxide); brominated polystyrene
KeywordsPlus: MISCIBILITY; COPOLYMERS; BEHAVIOR; SYSTEMS
Abstract: The miscibility of the binary and ternary blends of poly(2,6-dimethyl-1,4-phenylene oxide), brominated polystyrene, and polystyrene was investigated using a differential scanning calorimeter. The morphology of these blends was characterized by scanning electron microscopy. These studies revealed a close relation between the blend structure and its mechanical properties. The compatibilizing effect of poly(2,6-dimethyl-1,4-phenylene oxide) on the miscibility of the polystyrene/brominated polystyrene blends was examined. It was found that poly(2,6-dimethyl-1,4-phenylene oxide), which was miscible with polystyrene and partially miscible with brominated polystyrene, compatibilizes these two immiscible polymers if its contention exceeds 33 wt 9b. Upon the addition of poly(2,6-dimethyl-1,4-phenylene oxide) to the immiscible blends of polystyrene/brominated polystyrene, we observed a change in the morphology of the mixtures. An improvement in the mechanical properties was noticed. (C) 2000 John Wiley & Sons, Inc.
Times Cited: 0
Source item page count: 7
Publication Date: JAN 10
IDS No.: 262WG
29-char source abbrev: J APPL POLYM SCI
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012 USA


Record 20 of 108
Author(s): Haliloglu T; Bahar I
Title: Structure-based analysis of protein dynamics: Comparison of theoretical results for hen lysozyme with X-ray diffraction and NMR relaxation data
Source: PROTEINS-STRUCTURE FUNCTION AND GENETICS 1999, Vol 37, Iss 4, pp 654-667
Publisher: WILEY-LISS
Addresses: Bahar I, Bogazici Univ, Polymer Res Ctr, TR-80815 Bebek, Turkey
Bogazici Univ, Polymer Res Ctr, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
TUBITAK Adv Polymer Mat Res Ctr, Istanbul, Turkey
Author Keywords: Gaussian network model; NMR order parameters; crystallographic temperature factors; coupled motions; hen eggwhite lysozyme
KeywordsPlus: LOCAL CHAIN DYNAMICS; NORMAL-MODE ANALYSIS; EGG-WHITE LYSOZYME; MOLECULAR-DYNAMICS; HYDROGEN-EXCHANGE; FOLDED PROTEINS; VIBRATIONAL DYNAMICS; TEMPERATURE FACTORS; SINGLE-PARAMETER; FLUCTUATIONS
Abstract: An analytical approach based on Gaussian network model (GNM) is proposed for predicting the rotational dynamics of proteins. The method, previously shown to successfully reproduce X-ray crystallographic temperature factors for a series of proteins is extended here to predict bond torsional mobilities and reorientation of main chain amide groups probed by N-15-H nuclear magnetic resonance (NMR) relaxation, The dynamics of hen egg-white lysozyme (HEWL) in the folded state is investigated using the proposed approach. Excellent agreement is observed between theoretical results and experimental (X-ray diffraction and NMR relaxation) data. The analysis reveals the important role of coupled rotations, or cross-correlations between dihedral angle Librations, in defining the relaxation mechanism on a local scale. The crystal and solution structures exhibit some differences in their local motions, but their global motions are identical. Hinge residues mediating the cooperative movements of the alpha- and beta-domains are identified, which comprise residues in helix C, Glu35 and Ser36 on the loop succeeding helix B, Ile55 and Leu56 at the turn between strands II and III. The central part of the beta-domain long loop and the turn between strands I and II display an enhanced mobility. Finally, kinetically hot residues and key interactions are identified, which point at helix B and beta-strand III as the structural elements underlying the stability of the tertiary structure, Proteins 1999;37:654-667, (C) 1999 Wiley-Liss, Inc.
Times Cited: 2
Source item page count: 14
Publication Date: DEC 1
IDS No.: 261DK
29-char source abbrev: PROTEIN-STRUCT FUNCT GENET
Publisher address: DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012 USA


Record 21 of 108
Author(s): Kayaman N; Gurel EE; Baysal BM; Karasz FE
Title: Coil to globule transition behaviour of poly(methyl methacrylate) in isoamyl acetate
Source: POLYMER 2000, Vol 41, Iss 4, pp 1461-1468
Publisher: ELSEVIER SCI LTD
Addresses: Baysal BM, TUBITAK Marmara Res Ctr, Dept Chem, TR-41470 Gebze Kocaeli, Turkey
TUBITAK Marmara Res Ctr, Dept Chem, TR-41470 Gebze Kocaeli, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Univ Massachusetts, Dept Polymer Sci & Engn, Amherst, MA 01003 USA
Author Keywords: dynamic light scattering; coil-globule collapse; poly(methyl methacrylate)
KeywordsPlus: SINGLE-CHAIN; INTRINSIC-VISCOSITY; PHASE-TRANSITION; LIGHT-SCATTERING; POLYMER-CHAINS; COLLAPSE; POLYSTYRENE; CYCLOHEXANE; KINETICS; MACROMOLECULES
Abstract: The coil-globule transition behaviour of poly(methyl methacrylate) has been studied in isoamyl acetate by using the dynamic light scattering technique. The dimensions of the polymer show smooth and continuous contraction below a temperature (61.0 degrees C). The hydrodynamic size of PMMA in isoamyl acetate (M-w = 3.3 x 10(6) g mol(-1)) decreases to 41% in an unperturbed state at 18.4 degrees C. The temperature dependence of a chain contraction can be represented by a master curve in alpha(h)(3) \ tau \ M-w(1/2) vs \ tau \ M-w(1/2) plot, where alpha(h) = R-h/R-h,R-theta and tau = (T - theta)/theta. A high-chain density value implies that the highly collapsed globule contains 56% isoamyl acetate in its hydrodynamic volume. (C) 1999 Elsevier Science Ltd. All rights reserved.
Times Cited: 3
Source item page count: 8
Publication Date: FEB
IDS No.: 260BT
29-char source abbrev: POLYMER
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND


Record 22 of 108
Author(s): Eraslan S; Kayserili H; Apak MY; Kirdar B
Title: Identification of point mutations in Turkish DMD/BMD families using multiplex-single stranded conformation analysis (SSCA)
Source: EUROPEAN JOURNAL OF HUMAN GENETICS 1999, Vol 7, Iss 7, pp 765-770
Publisher: STOCKTON PRESS
Addresses: Kirdar B, Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Duzen Labs, Div Mol Genet, Istanbul, Turkey
Istanbul Univ, Inst Child Hlth, Div Med Genet, Istanbul, Turkey
Author Keywords: DMD/BMD; point mutations; multiplex single-stranded conformation analysis; (SSCA); nonsense mutation; missense mutation
KeywordsPlus: HUMAN DYSTROPHIN GENE; POLYMORPHISM SSCP; MISSENSE MUTATION; DELETION; DOMAIN
Abstract: Small mutations are the cause of the disease in one third of cases of Duchenne and Becker muscular dystrophy (DMD/BMD), The identification of point mutations in the dystrophin gene is considered to be very important, because it may provide new insights into the function of dystrophin and direct information for genetic counselling, In this study, we have screened 18 deletion-prone exons (25.5% of the coding region) of the dystrophin gene by using a modified non-isotopic multiplex single-stranded conformation analysis (SSCA). Mutations responsible for the disease phenotype could be identified in five out of 56 unrelated DMD/BMD patients without detectable deletions, Two of these mutations, 980-981delCC and 719G > C, are novel mutations which have not been described previously. Four of the five mutations, including 980-981delCC detected in this study are found to be nonsense or frameshift mutations leading to the synthesis of a truncated dystrophin protein. The missense mutation, 719G > C, causing the substitution of highly conserved alanine residue at 171 with proline in the actin binding domain of the dystrophin, is associated with a BMD phenotype. This study also revealed the presence of six polymorphisms in Turkish DMD/BMD patients.
Times Cited: 0
Source item page count: 6
Publication Date: OCT-NOV
IDS No.: 254LX
29-char source abbrev: EUR J HUMAN GENET
Publisher address: HOUNDMILLS, BASINGSTOKE RG21 6XS, HAMPSHIRE, ENGLAND


Record 23 of 108
Author(s): Kurt N; Haliloglu T
Title: Conformational dynamics of chymotrypsin inhibitor 2 by coarse-grained simulations
Source: PROTEINS-STRUCTURE FUNCTION AND GENETICS 1999, Vol 37, Iss 3, pp 454-464
Publisher: WILEY-LISS
Addresses: Haliloglu T, Bogazici Univ, Ctr Polymer Res, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Ctr Polymer Res, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: low resolution model; knowledge-based potentials; dynamic Monte Carlo; fluctuations; virtual bond rotations; orientational and conformational correlations
KeywordsPlus: SEQUENCE-STRUCTURE MATCHES; KNOWLEDGE-BASED POTENTIALS; MONTE-CARLO SIMULATIONS; LATTICE MODEL; MOLECULAR-DYNAMICS; GLOBULAR-PROTEINS; TRANSITION-STATE; COMPUTER-SIMULATION; X-RAY; PREDICTION
Abstract: A coarse-grained dynamic Monte Carlo (MC) simulation method is used to investigate the conformational dynamics of chymotrypsin inhibitor 2 (CI2). Each residue is represented therein by two interaction sites, one at the alpha-carbon and the other on the amino acid side-chain. The energy and geometry parameters extracted from databank structures are used. The calculated rms fluctuations of alpha-carbon atoms are in good agreement with crystallographic temperature factors. The two regions of the protein that pack against each other to form the main hydrophobic core exhibit negatively correlated fluctuations. The conformational dynamics could efficiently be probed by the time-delayed orientational and conformational correlation functions of the virtual bonds: the active site loop, excluding the active site bond, the turn region, and the N-terminal of the alpha-helix are relatively more mobile regions of the structure. A correlation is observed between the hydrogen/deuterium (H/D) exchange behavior and the long-time orientational and conformational autocorrelation function values for CI2. A cooperativity in the rotations of the bonds near in sequence is observed at all time windows, whereas the cooperative rotations of the bonds far along the sequence appear at long time windows; these correlations contribute to the stability of the secondary structures and the tertiary structure, respectively. Proteins 1999;37:454-464. (C) 1999 Wiley-Liss, Inc.
Times Cited: 2
Source item page count: 11
Publication Date: NOV 15
IDS No.: 251DM
29-char source abbrev: PROTEIN-STRUCT FUNCT GENET
Publisher address: DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012 USA


Record 24 of 108
Author(s): Haliloglu T
Title: Conformational dynamics of cytochrome C by coarse-grained simulations.
Source: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 1999, Vol 218, pp 189-PMSE-
Publisher: AMER CHEMICAL SOC
Addresses: Bogazici Univ, Ctr Polymer Res, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Times Cited: 0
Source item page count: 1
Publication Date: AUG 22
Part number: 2
IDS No.: 226RA
29-char source abbrev: ABSTR PAP AMER CHEM SOC
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036 USA


Record 25 of 108
Author(s): Jernigan RL; Demirel MC; Bahar I
Title: Relating structure to function through the dominant slow modes of motion of DNA topoisomerase II
Source: INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY 1999, Vol 75, Iss 3, pp 301-312
Publisher: JOHN WILEY & SONS INC
Addresses: Jernigan RL, NCI, Div Basic Sci, Lab Expt & Computat Biol, Mol Struct Sect,NIH, Bethesda, MD 20892 USA
NCI, Div Basic Sci, Lab Expt & Computat Biol, Mol Struct Sect,NIH, Bethesda, MD 20892 USA
Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Bogazici Univ, Polymer Res Ctr, Istanbul, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, TR-80815 Istanbul, Turkey
Author Keywords: topoisomerase; Gaussian network model; DNA binding proteins; slow modes of motion
KeywordsPlus: VIBRATIONAL DYNAMICS; RESIDUE POTENTIALS; GLOBULAR-PROTEINS; FOLDED PROTEINS; FLUCTUATIONS; LYSOZYME; MACROMOLECULES; SIMULATIONS; MECHANISM; NETWORKS
Abstract: Type II DNA topoisomerases are enzymes capable of transporting one DNA duplex through another by performing a cycle of DNA cleavage, transport, and religation, coupled to ATP binding and hydrolysis. Here, we considered a coarse-grained model of the structure and investigated the motions within two structures, DNA topoisomerase II and DNA gyrase A. The coarse graining with only one point per residue means that motions in such large proteins can be thoroughly investigated. The overall motions are reflected in the crystallographic temperature factors, which are reproduced by the model. Also, with this approach, we can view the slowest, most cooperative, modes of motion, corresponding to the largest-scale correlated motions in the protein. These motions are nearly identical in the two proteins and are likely related to individual steps in the enzyme's complex mechanism of activity. (C) 1999 John Wiley & Sons, Inc.*.
Times Cited: 3
Source item page count: 12
Publication Date: NOV 5
IDS No.: 247BR
29-char source abbrev: INT J QUANTUM CHEM
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012 USA


Record 26 of 108
Author(s): Haliloglu T
Title: Coarse-grained simulations of the conformational dynamics of proteins
Source: COMPUTATIONAL AND THEORETICAL POLYMER SCIENCE 1999, Vol 9, Iss 3-4, pp 255-260
Publisher: ELSEVIER SCI LTD
Addresses: Bogazici Univ, Ctr Polymer Res, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: Monte Carlo/Metropolis simulation technique; virtual bonds; conformational dynamics; autocorrelations; unfolding alpha-helices; beta-sheets
KeywordsPlus: SEQUENCE-STRUCTURE MATCHES; KNOWLEDGE-BASED POTENTIALS; PIG ALPHA-LACTALBUMIN; MOLTEN GLOBULE STATE; HYDROGEN-EXCHANGE; CYTOCHROME-C; BARNASE; NMR; RESOLUTION; STABILITY
Abstract: The conformational dynamics of a set of proteins, cytochrome c, alpha-lactalbumin and barnase, is studied by an off-lattice Monte Carlo (MC)/Metropolis simulation technique. A low-resolution model (virtual bond model) for the protein structure is used with recently extracted knowledge-based potentials. The calculated root-mean-square fluctuations in the alpha-carbons are in good agreement with X-ray crystallographic temperature factors. The potentially yielding or non-yielding regions of the protein for unfolding, in the kinetic sense, are identified from the correlation analysis of the rotational motions of the backbone bonds. The bonds which display highly auto-correlated rotational motions, in general, belong to those regions which are experimentally identified to be highly resistant to unfolding. (C) 1999 Elsevier Science Ltd. All rights reserved.
Times Cited: 1
Source item page count: 6
IDS No.: 230TM
29-char source abbrev: COMPUT THEOR POLYM SCI
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND


Record 27 of 108
Author(s): Haliloglu T; Mattice WL
Title: Detection of the onset of demixing in simulations of polypropylene melts in which the chains differ only in stereochemical composition
Source: JOURNAL OF CHEMICAL PHYSICS 1999, Vol 111, Iss 9, pp 4327-4333
Publisher: AMER INST PHYSICS
Addresses: Mattice WL, Univ Akron, Inst Polymer Sci, Akron, OH 44325 USA
Univ Akron, Inst Polymer Sci, Akron, OH 44325 USA
Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Bogazici Univ, Ctr Polymer Res, Istanbul, Turkey
TUBITAK Adv Polymer Mat Res Ctr, TR-80815 Bebek, Turkey
KeywordsPlus: HIGH-COORDINATION LATTICE; ANGLE NEUTRON-SCATTERING; POLYMER BLENDS; THERMODYNAMIC INTERACTIONS; ATACTIC POLYPROPYLENE; POLYBUTADIENE BLENDS; POLYOLEFIN BLENDS; PHASE-BEHAVIOR; STATE; DYNAMICS
Abstract: Simulations have been performed at 480 K for pure melts of atactic, isotactic and syndiotactic polypropylene chains with a degree of polymerization of 50 and composition C150H302, and also for the three 50:50 mixtures of two of these species. The simulations are performed on a high coordination lattice, with incorporation of short range intramolecular interactions from a rotational isomeric state model of polypropylene, and incorporation of long range interactions defined by a Lennard-Jones potential energy function for the interaction of pairs of molecules of propane. Both the rotational isomeric state model and Lennard-Jones parameters were taken directly from the literature (Suter and Prausnitz, respectively). The efficiency of the simulation on the sparsely occupied high coordination lattice facilitates the equilibration of the one- and two-component melts within accessible computer time. Onset of a tendency for demixing of isotactic and syndiotactic polypropylene is apparent in the intermolecular pair correlation functions. No such demixing occurs with isotactic and atactic polypropylene. Both of these predictions from the simulation are consistent with experimental results in the literature (Maier and Lohse, respectively). The simulation produces an ambigious prediction for the melt of atactic and syndiotactic polypropylene. This melt has been reported (Maier ) to exhibit phase separation, but less strongly than the isotactic-syndiotactic system, for which the simulation makes an unambiguous (and correct) prediction. The physical origin of the tendency for demixing in the simulations is identified as the differences in the preferred local conformations of polypropylene chains with various stereochemical sequences. This driving force is an example of "conformational asymmetry" induced solely by differences in stereochemical sequence. (C) 1999 American Institute of Physics. [S0021-9606(99)51433-5].
Times Cited: 6
Source item page count: 7
Publication Date: SEP 1
IDS No.: 228BM
29-char source abbrev: J CHEM PHYS
Publisher address: CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA


Record 28 of 108
Author(s): Demircan M; Camurdan MC; Postlethwaite BE
Title: On-line learning Fuzzy Relational Model based dynamic matrix control of an openloop unstable process
Source: CHEMICAL ENGINEERING RESEARCH & DESIGN 1999, Vol 77, Iss A5, pp 421-428
Publisher: INST CHEMICAL ENGINEERS
Addresses: Camurdan MC, Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Univ Strathclyde, Chem & Proc Engn Dept, Glasgow, Lanark, Scotland
Author Keywords: dynamic matrix control; fuzzy relational models; adaptive control
KeywordsPlus: PREDICTIVE CONTROL
Abstract: Fuzzy Relational Models (FRM) are used when implementing a dynamic matrix control (DMC) algorithm on a nonlinear process which exhibits multiplicity of steady state solutions. Following Ozkan(1), Ozkan and Camurdan(2), the openloop unstable equilibrium point of the process is first stabilized by an analog proportional only controller. DMC is then used to control this stabilized system. Both servo and regulatory control are investigated. Locally and globally obtained fixed and globally obtained variable FRMs are used. In some runs the recursive least squares (RLS) algorithm is also used to update the relational array so as to provide on-line learning. It is shown by simulations that FRMs that are identified in a local region performed as well as those that are identified in the whole operating region. On the other hand the performance of the system was found to be poor if a variable model is used.
Times Cited: 1
Source item page count: 8
Publication Date: JUL
IDS No.: 227FJ
29-char source abbrev: CHEM ENG RES DES
Publisher address: 165-189 RAILWAY TERRACE, DAVIS BLDG, RUGBY CV21 3BR, ENGLAND


Record 29 of 108
Author(s): Gurel EE; Kayaman N; Baysal BM; Karasz FE
Title: Dynamic light scattering studies of atactic and syndiotactic poly(methyl methacrylate)s in dilute theta solution
Source: JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS 1999, Vol 37, Iss 16, pp 2253-2260
Publisher: JOHN WILEY & SONS INC
Addresses: Baysal BM, Tubitak Marmara Res Ctr, Dept Chem, TR-41470 Gebze Kocaeli, Turkey
Tubitak Marmara Res Ctr, Dept Chem, TR-41470 Gebze Kocaeli, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Univ Massachusetts, Dept Polymer Sci & Engn, Amherst, MA 01003 USA
Author Keywords: dynamic light scattering; coil-globule transitions; poly(methyl methacrylate)
KeywordsPlus: LINEAR POLYMER DIMENSIONS; COIL-GLOBULE TRANSITION; POLYSTYRENE-CYCLOHEXANE SYSTEM; SINGLE-CHAIN; INTRINSIC-VISCOSITY; TEMPERATURE-DEPENDENCE; MIXTURE 1-CHLOROBUTANE; 3-COMPONENT SYSTEMS; HOMOPOLYMER CHAIN; ISOAMYL ACETATE
Abstract: The present article considers the coil-to-globule transition behavior of atactic and syndiotactic poly(methyl methacrylates), (PMMA) in their theta solvent, n-butyl chloride (nBuCl). Changes in Rh in these polymers with temperature in dilute theta solutions were investigated by dynamic light scattering. The hydrodynamic size of atactic PMMA (a-PMMA-1) in nBuCl (M-w: 2.55 x 10(6) g/mol) decreases to 61% of that in the unperturbed state at 13.0 degrees C. Atactic PMMA (a-PMMA-2) with higher molecular weight (M-w: 3.3 x 10(6) g/mol) shows higher contraction in the same theta solvent (alpha(eta) = R-h(T)IRh (theta) = 0.44) at a lower temperature, 7.25 degrees C. Although syndiotactic PMMA (s-PMMA) has lower molecular weight than that of atactic samples (M-w: 1.2 x 10(6)), a comparable chain collapse was observed (alpha(eta) = 0.63) at 9.0 degrees C. (C) 1999 John Wiley & Sons, Inc.
Times Cited: 4
Source item page count: 8
Publication Date: AUG 15
IDS No.: 221HM
29-char source abbrev: J POLYM SCI B-POLYM PHYS
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012 USA

Record 30 of 108
Author(s): Bahar I; Jernigan RL
Title: Subunit communication, processing and fluctuations in tryptophan synthase
Source: BIOPHYSICAL JOURNAL 1999, Vol 76, Iss 1, pp A115-A115
Publisher: BIOPHYSICAL SOCIETY
Addresses: NCI, Lab Exp & Comp Biol, NIH, Bethesda, MD 20892 USA
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Ctr Polymer Res, TR-80815 Bebek, Turkey
TUBITAK, Adv Polym Mat Res Ctr, Istanbul, Turkey
Times Cited: 0
Source item page count: 1
Publication Date: JAN
Part number: 2
IDS No.: 210BU
29-char source abbrev: BIOPHYS J
Publisher address: 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA


Record 31 of 108
Author(s): Aksoylu AE; Isli AI; Onsan ZI
Title: Interaction between nickel and molybdenum in Ni-Mo/Al2O3 catalysts: III. Effect of impregnation strategy
Source: APPLIED CATALYSIS A-GENERAL 1999, Vol 183, Iss 2, pp 357-364
Publisher: ELSEVIER SCIENCE BV
Addresses: Onsan ZI, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: nickel-alumina; nickel-molybdenum alumina; impregnation; CO hydrogenation; CO2 methanation
KeywordsPlus: CO HYDROGENATION; KINETICS
Abstract: Bimetallic 5 wt.% Ni-5 wt.% Mo/Al2O3 catalysts prepared by sequential impregnation and coimpregnation were tested for their physical properties, activity, and selectivity characteristics in COx hydrogenation at 523-598 K using different feed compositions. Experimental results show that the coimpregnated Ni-Mo catalyst has the highest active metal surface area. Specific activities and activation energies for CO2 methanation on coimpregnated and sequentially impregnated catalysts indicate that the nature of the synergetic interaction is not affected by the impregnation sequence. CO hydrogenation at relatively high C/H ratios and temperatures above 548 K is accompanied by activity losses on all samples due to carbon deposition. Although there is no significant relation between carbon deposition and C-2-C-4 selectivities, a positive effect on olefin to paraffin ratios is observed at intermediate temperatures. (C) 1999 Elsevier Science B.V. All rights reserved.
Times Cited: 0
Source item page count: 8
Publication Date: JUL 19
IDS No.: 206YF
29-char source abbrev: APPL CATAL A-GEN
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 32 of 108
Author(s): Sen TZ; Bahar I; Erman B; Laupretre F; Monnerie L
Title: Local dynamics of cis-1,4-polybutadiene and cis-1,4-polyisoprene. A comparative study based on cooperative kinematics theory and NMR experiments
Source: MACROMOLECULES 1999, Vol 32, Iss 9, pp 3017-3024
Publisher: AMER CHEMICAL SOC
Addresses: Bahar I, Bogazici Univ, Ctr Polymer Res, Dept Chem Engn, TR-80815 Istanbul, Turkey
Bogazici Univ, Ctr Polymer Res, Dept Chem Engn, TR-80815 Istanbul, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, TR-80815 Istanbul, Turkey
Sabanci Univ, Fac Engn & Nat Sci, TR-80020 Istanbul, Turkey
Ecole Super Phys & Chim Ind, PCSM, F-75231 Paris 05, France
KeywordsPlus: GLASS-TRANSITION TEMPERATURE; MOLECULAR-DYNAMICS; CHAIN DYNAMICS; POLYMER-CHAINS; AMORPHOUS POLYBUTADIENES; BULK POLYBUTADIENES; DENSE MEDIA; POLYISOPRENE; RELAXATION; SIMULATION
Abstract: Cooperative motions of cis-1,4-polybutadiene (cis-PB) and cis-1,4-polyisoprene (cis-PI) in the bulk state are analyzed and compared using the cooperative kinematics (CK) theory. The mechanisms of relaxation on a local scale are closely similar for the two polymers in dense media, resulting from the same geometry of the backbone, which is the major determinant of the types of accessible cooperative conformational rearrangements. The correlation times for the reorientation of C-H bonds of cis-PI are found to be about 1 order of magnitude longer than those for cis-PB at the same effective friction coefficient. The results are in accordance with previous NMR experiments which indicated a ratio of about 10. The molecular characteristics responsible for this difference in the local mobilities of the two polymers are examined. Three sources are identified: (i) the excess volume swept by the moving units in cis-PI due to the CH3 units appended to the backbone, (ii) the higher short-range conformational potential energies in cis-PI compared to those in cis-PB, and (iii) the restriction in the number of accessible isomeric transitions in cis-PI compared to those of cis-PB, which is due to the excluded-volume effect.
Times Cited: 1
Source item page count: 8
Publication Date: MAY 4
IDS No.: 194EM
29-char source abbrev: MACROMOLECULES
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036 USA


Record 33 of 108
Author(s): Altintas MM; Ulgen KO
Title: Growth of Thermus aquaticus and its TaqI endonuclease production
Source: ACTA BIOTECHNOLOGICA 1999, Vol 19, Iss 1, pp 45-56
Publisher: WILEY-V C H VERLAG GMBH
Addresses: Ulgen KO, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
KeywordsPlus: EXTRACELLULAR PROTEINASE
Abstract: The culture behaviour of Thermus aquaticus was characterized. The response of the bacterium to various carbon (tryptone, glucose, glycerol) and nitrogen sources (yeast extract, NaNO3, (NH4)(2)SO4, leucine, thymine, thiamine, glutamic acid) was studied. Amino acids did not support growth, but CASTENHOLZ salt medium supplemented with yeast extract and glucose or tryptone resulted in good growth and production. A suitable medium composition giving the highest biomass concentration and enzyme yield was developed. The simple medium containing TYE-NaCl resulted in the highest biomass concentration, whereas CASTENHOLZ mineral medium supplemented with tryptone and yeast extract gave the highest specific activity and enzyme yield. The effect of inoculum age and size on growth was also investigated in order to improve the yield and process consistency. The use of shake flasks inoculated with precultures at their early or late stationary phase resulted in the same biomass concentration (0.560 +/- 0.015 g/l) and similar maximum specific growth rates (0.258 +/- 0.003 h(-1)). Inoculum sizes between 1 and 2.5 per cent were optimal for cell growth. As the other papers on thermophilic microorganisms, including the T. aquaticus YT 1 strain, gave qualitative information on growth, the results presented hen cannot be compared with others on a quantitative basis. TaqI endonuclease was purified using a 5 step protocol including cell disruption, adsorption, precipitation, column chromatography and final dialysis. The enriched fraction had a specific activity of 33,600 U TaqI endonuclease per mg protein.
Times Cited: 0
Source item page count: 12
IDS No.: 188NP
29-char source abbrev: ACTA BIOTECHNOL
Publisher address: MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY


Record 34 of 108
Author(s): Akin AN; Aksoylu AE; Onsan ZI
Title: Adsorption and reaction studies on cobalt/alumina catalysts prepared by changing pH coprecipitation
Source: REACTION KINETICS AND CATALYSIS LETTERS 1999, Vol 66, Iss 2, pp 393-399
Publisher: ELSEVIER SCIENCE BV
Addresses: Onsan ZI, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Author Keywords: coprecipitation; Co/Al2O3; adsorption of CO; H-2 and O-2
KeywordsPlus: CO HYDROGENATION ACTIVITY; NICKEL-ALUMINA CATALYSTS; COBALT-ALUMINA; SUPPORT
Abstract: Co/Al2O3 catalysts prepared by changing pH coprecipitation with Co loadings in the 8.7-36 wt.% range were analyzed by TSA, TPV, pore structure, XRD as well as CO, H-2, O-2 adsorption and CO hydrogenation. High O-2 uptake and reducibility coupled with low dispersion and constant MSA above 17 wt.% Co indicate large crystallites that are less exposed to H-2. CO hydrogenation per Co site decreases with increasing dispersion or decreasing metal loading.
Times Cited: 1
Source item page count: 7
Publication Date: MAR
IDS No.: 182NH
29-char source abbrev: REACT KINET CATAL LETT
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 35 of 108
Author(s): Bahar I; Jernigan RL
Title: Cooperative fluctuations and subunit communication in tryptophan synthase
Source: BIOCHEMISTRY 1999, Vol 38, Iss 12, pp 3478-3490
Publisher: AMER CHEMICAL SOC
Addresses: Jernigan RL, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Ctr Polymer Res, TR-80815 Bebek, Istanbul, Turkey
TUBITAK Adv Polymer Mat Res Ctr, TR-80815 Bebek, Istanbul, Turkey
NCI, Mol Struct Sect, Lab Expt & Computat Biol, Div Basic Sci,NIH, Bethesda, MD 20892 USA
KeywordsPlus: ALPHA(2)BETA(2) COMPLEX REVEALS; INDUCED CONFORMATIONAL-CHANGES; ALPHA-SUBUNIT; SALMONELLA-TYPHIMURIUM; ESCHERICHIA-COLI; FLEXIBLE LOOP; TRIOSEPHOSPHATE ISOMERASE; BIENZYME COMPLEX; BETA-SUBUNIT; INTERSUBUNIT COMMUNICATION
Abstract: Tryptophan synthase (TRPS), with linearly arrayed subunits alpha beta beta alpha, catalyzes the last two reactions in the biosynthesis of L-tryptophan. The two reactions take place in the respective alpha- and beta-subunits of the enzyme, and the intermediate product, indole, is transferred from the alpha- to the beta-site through a 25 Angstrom long hydrophobic tunnel. The occurrence of a unique ligand-mediated long-range cooperativity for substrate channeling, and a quest to understand the mechanism of allosteric control and coordination in metabolic cycles, have motivated many experimental studies on the structure and catalytic activity of the TRPS alpha(2)beta(2) complex and its mutants. The dynamics of these complexes are analyzed here using a simple but rigorous theoretical approach, the Gaussian network model, Both wild-typo and mutant structures, in the unliganded and various liganded forms, are considered. The substrate binding site in the beta-subunit is found to be closely coupled to a group of hinge residues (beta 77-beta 89 and beta 376-beta 379) near the beta-beta interface. These residues simultaneously control the anticorrelated motion of the two beta-subunits, and the opening or closing of the hydrophobic tunnel. The latter process is achieved by the large amplitude fluctuations of the so-called COMM domain in the same subunit. Intersubunit communications are strengthened in the presence of external aldimines bound to the beta-site. The motions of the COMM core residues are coordinated with those of the alpha-beta hinge residues beta 174-beta 179 on the interfacial helix beta H6 at the entrance of the hydrophobic tunnel. And the motions of beta H6 are coupled, via helix beta HI and alpha L6, to those of the loop alpha L2 that includes the alpha-subunit catalytically active residue Asp60. Overall, our analysis sheds light on the molecular machinery underlying subunit communication, and identifies the residues playing a key role in the cooperative transmission of conformational motions across the two reaction sites.
Times Cited: 11
Source item page count: 13
Publication Date: MAR 23
IDS No.: 182QY
29-char source abbrev: BIOCHEMISTRY-USA
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036 USA


Record 36 of 108
Author(s): Haliloglu T
Title: Characterization of internal motions of Escherichia coli ribonuclease H by Monte Carlo simulation
Source: PROTEINS-STRUCTURE FUNCTION AND GENETICS 1999, Vol 34, Iss 4, pp 533-539
Publisher: WILEY-LISS
Addresses: Haliloglu T, Bogazici Univ, Polymer Res Ctr, TR-80815 Bebek, Turkey
Bogazici Univ, Polymer Res Ctr, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Author Keywords: E-coli; NMR; RNase; hydrogen exchange; virtual bonds; Monte Carlo simulation technique; conformational dynamics; auto- and cross-correlation
KeywordsPlus: GLOBULAR-PROTEINS; RESOLUTION; ALGORITHM; RESIDUES; DYNAMICS; MODEL
Abstract: The backbone dynamics of Escherichia coli ribonuclease H (RNase H) is studied by a recently developed off-lattice Monte Carlo/Metropolis simulation technique. A low-resolution model (virtual-bond model) is used together with knowledge-based potentials. The calculated mean-square fluctuations in alpha carbons are in good agreement with crystallographic temperature factors. The conformations generated around the native state are analyzed by time-dependent orientational and conformational correlation functions to study the internal motions of RNase at different time windows. A correlation between the free-energy changes for native-state hydrogen exchange (HX) and the extent of the autocorrelation in the rotations of the virtual bonds at long times has been observed. Crosscorrelations between the rotations of the bonds, which are near-neighbor in the sequence, are effective in all time windows and help the secondary structures to preserve their kinetic stability. On the other hand, the existence of cross-correlations at long times help the tertiary contacts be maintained. The order parameter of NH bond vector for each residue has been calculated and compared with N-15-NMR relaxation measurements. Proteins 1999;34:533-539. (C) 1999 Wiley-Liss, Inc.
Times Cited: 3
Source item page count: 7
Publication Date: MAR 1
IDS No.: 173DA
29-char source abbrev: PROTEIN-STRUCT FUNCT GENET
Publisher address: DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012 USA


Record 37 of 108
Author(s): Onay T; Kayserili H; Apak MY; Kirdar B
Title: Analysis of infertile brothers with congenital bilateral absence of vas deferens for mutations in the CFTR gene
Source: CLINICAL GENETICS 1999, Vol 55, Iss 1, pp 63-64
Publisher: MUNKSGAARD INT PUBL LTD
Addresses: Kirdar B, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
KeywordsPlus: CYSTIC-FIBROSIS
Times Cited: 0
Source item page count: 2
Publication Date: JAN
IDS No.: 165VT
29-char source abbrev: CLIN GENET
Publisher address: 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK


Record 38 of 108
Author(s): Kayaman N; Hamurcu EEG; Uyanik N; Baysal BM
Title: Interpenetrating hydrogel networks based on polyacrylamide and poly(itaconic acid): synthesis and characterization
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS 1999, Vol 200, Iss 1, pp 231-238
Publisher: WILEY-V C H VERLAG GMBH
Addresses: Hamurcu EEG, TUBITAK, Marmara Res Ctr, Dept Chem, POB 21, TR-41470 Gebze, Kocaeli, Turkey
TUBITAK, Marmara Res Ctr, Dept Chem, TR-41470 Gebze, Kocaeli, Turkey
Istanbul Tech Univ, Dept Chem, TR-80626 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
KeywordsPlus: POLY(ACRYLIC ACID); POLYMER NETWORKS; POLY(VINYL ALCOHOL); DRUG-RELEASE; PH; GELS; POLY(DIMETHYLSILOXANE); DELIVERY; BEHAVIOR; GELATIN
Abstract: The synthesis of sequential and simultaneous semi-interpenetrating hydrogel networks (IPNs) based on polyacrylamide (PAAm) and poly(itaconic acid) (PICA) is described. Polyacrylamide was used as a host polymer. Physical properties of IPN hydrogels were determined by IR, swelling, extraction and density measurements. No indication for the formation of hydrogen-bonded complexation was observed by LR spectroscopy. The extraction results showed that the grafting level between the two components of PAAm/PICA in simultaneous semi-IPN is higher than that observed in sequential IPNS. These results confirm that the decrease in swelling ratios with PICA contents is probably due to the entanglement effect. The properties of IPN hydrogels were found to be dependent on the composition and the type of IPN. Both sequential and simultaneous IPNs have quite different morphologies compared to the pure PAAm host hydrogel.
Times Cited: 3
Source item page count: 8
Publication Date: JAN
IDS No.: 159WV
29-char source abbrev: MACROMOL CHEM PHYSICS
Publisher address: MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY


Record 39 of 108
Author(s): Keskin O; Bahar I
Title: Packing of sidechains in low-resolution models for proteins
Source: FOLDING & DESIGN 1998, Vol 3, Iss 6, pp 469-479
Publisher: CURRENT BIOLOGY LTD
Addresses: Bahar I, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Polymer Res Ctr, TR-80815 Bebek, Turkey
TUBITAK Adv Polymer Mat Res Ctr, TR-80815 Bebek, Turkey
Author Keywords: hydrophobic core; sidechain isomers; sidechain packing; specific interactions; virtual bond model
KeywordsPlus: SIDE-CHAIN CONFORMATIONS; HOMOLOGOUS PROTEINS; GLOBULAR-PROTEINS; BACKBONE; PREDICTION; ENERGY; POTENTIALS; ALGORITHM; DISCRETE; ENTROPY
Abstract: Background: Atomic level rotamer libraries for sidechains in proteins have been proposed by several groups. Conformations of side groups in coarse-grained models, on the other hand, have not yet been analyzed, although low resolution approaches are the only efficient way to explore global structural features.

Results: A residue-specific backbone-dependent library for sidechain isomers, compatible with a coarse-grained model, is proposed. The isomeric states are utilized in packing sidechains of known backbone structures. Sidechain positions are predicted with a root-mean-square deviation (rmsd) of 2.40 Angstrom with respect to crystal structure for 50 test proteins. The rmsd for core residues is 1.60 Angstrom and decreases to 1.35 Angstrom when conformational correlations and directional effects in inter-residue couplings are considered.

Conclusions: An automated method for assigning sidechain positions in coarse-grained model proteins is proposed and made available on the internet; the method accounts satisfactorily for sidechain packing, particularly in the core.

Times Cited: 0
Source item page count: 11
IDS No.: 157CK
29-char source abbrev: FOLD DES
Publisher address: 84 THEOBALDS RD, LONDON WC1X 8RR, ENGLAND


Record 40 of 108
Author(s): Altintas MM; Ozer N; Ulgen KO
Title: Purification of TaqI endonuclease from Thermus aquaticus
Source: JOURNAL OF CHROMATOGRAPHY A 1998, Vol 828, Iss 1-2, pp 373-381
Publisher: ELSEVIER SCIENCE BV
Addresses: Ulgen KO, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: Thermus aquaticus; TaqI endonuclease; enzymes; purification
KeywordsPlus: RESTRICTION ENDONUCLEASE
Abstract: A purification procedure for the thermostable restriction enzyme TaqI was developed using high-performance ion-exchange liquid chromatography. The effects of various operating conditions on the separation behaviour of TaqI endonuclease from the cell extracts were investigated for optimisation and scaling up. The separation of the enzyme by HPLC was found to be strongly dependent on the sample volume, slope of linear gradient and order of the ion-exchange columns. The final yield of the enzyme is also dependent to a great extent upon the number of fractionation steps employed to purify the enzyme. In the present study, 4000 U TaqI endonuclease per mg protein was recovered from 2 g Thermus aquaticus cells with a two-step purification protocol in one day. The purification factor was 24. Compared to other classical methods of purification reported in literature with 4000 or 32 000 U enzyme from 200 g of Thermus aquaticus cells, HPLC yielded 190 000 U enzyme from 200 g cells using cation and anion HPLC columns sequentially and thus resulted in a higher efficiency. (C) 1998 Elsevier Science B.V. All rights reserved.
Times Cited: 2
Source item page count: 9
Publication Date: DEC 18
IDS No.: 152ZP
29-char source abbrev: J CHROMATOGR A
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 41 of 108
Author(s): Karal O; Hamurcu EEG; Baysal BM
Title: Effect of a triblock PCL-PDMS-PCL copolymer on the properties of immiscible poly(vinylchloride)/poly(2-ethylhexylacrylate) blends
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS 1998, Vol 199, Iss 12, pp 2699-2708
Publisher: WILEY-V C H VERLAG GMBH
Addresses: Baysal BM, Tubitak, Marmara Res Ctr, Dept Chem, POB 21, TR-41470 Gebze, Kocaeli, Turkey
Tubitak, Marmara Res Ctr, Dept Chem, TR-41470 Gebze, Kocaeli, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
KeywordsPlus: POLYMER BLENDS; POLY(METHYL METHACRYLATE); MISCIBILITY BEHAVIOR; POLY(VINYL CHLORIDE); TERNARY BLENDS; POLY(STYRENE-GRAFT-ETHYLENE OXIDE); POLYVINYL-CHLORIDE) BLENDS; POLY(ETHYL METHACRYLATE); PHASE-BEHAVIOR; COMPATIBILITY
Abstract: Miscibility, thermal, mechanical and morphological properties of poly(vinyl chloride)/poly(2-ethylhexyl acrylate), (PVC/PEHA) blends containing 1-10 wt.-% of the triblock copolymer polycaprolactone-block-poly(dimethylsiloxane)-block-(PCL-PDMS-PCL, Tegomer) were investigated by several techniques. Binary blends of PVC/PEHA are found to be immiscible according to differential scanning calorimetry and viscosity measurements. The effect of Tegomer addition on the properties of blends was examined. Ternary blends of PVC/PEHA/Tegomer exhibited a single T-g behaviour and viscosity measurements indicate some compatibility. Stress-strain results showed that Tegomer has a synergetic effect on the flexibility of the blends. FTIR analysis confirms the specific interactions between the components in ternary blends of PVC/PEHA/Tegomer. Morphological properties of the blends were examined by scanning electron microscopy.
Times Cited: 1
Source item page count: 10
Publication Date: DEC
IDS No.: 150JE
29-char source abbrev: MACROMOL CHEM PHYSICS
Publisher address: MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY


Record 42 of 108
Author(s): Keskin O; Bahar I; Badretdinov AY; Ptitsyn OB; Jernigan RL
Title: Empirical solvent-mediated potentials hold for both intra-molecular and inter-molecular inter-residue interactions
Source: PROTEIN SCIENCE 1998, Vol 7, Iss 12, pp 2578-2586
Publisher: CAMBRIDGE UNIV PRESS
Addresses: Jernigan RL, NCI, Mol Struct Sect, Math Biol Lab, Div Basic Sci,NIH, Bethesda, MD 20892 USA
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Polymer Res Ctr, TR-80815 Bebek, Istanbul, Turkey
TUBITAK Adv Polymer Mat Res Ctr, TR-80815 Bebek, Istanbul, Turkey
NCI, Mol Struct Sect, Lab Expt & Computat Biol, Div Basic Sci,NIH, Bethesda, MD 20892 USA
Rockefeller Univ, Lab Mol Biophys, New York, NY 10021 USA
Russian Acad Sci, Inst Prot Res, Pushchino 142292, Moscow Region, Russia
Author Keywords: knowledge-based potentials; protein interfaces; protein solvation
KeywordsPlus: QUASI-CHEMICAL APPROXIMATION; PROTEIN-PROTEIN INTERFACES; SEQUENCE-STRUCTURE MATCHES; KNOWLEDGE-BASED POTENTIALS; GLOBULAR-PROTEINS; ENERGY FUNCTIONS; RECOGNITION; CORRECT
Abstract: Whether knowledge-based intra-molecular inter-residue potentials are valid to represent inter-molecular interactions taking place at protein-protein interfaces has been questioned in several studies. Differences in the chain connectivity effect and in residue packing geometry between interfaces and single chain monomers have been pointed out as possible sources of distinct energetics for the two cases. In the present study, the interfacial regions of protein-protein complexes are examined to extract inter-molecular inter-residue potentials, using the same statistical methods as those previously adopted for intra-molecular residue pairs. Two sets of energy parameters are derived, corresponding to solvent-mediation and "average residue" mediation. The former set is shown to be highly correlated (correlation coefficient 0.89) with that previously obtained for inter-residue interactions within single chain monomers, while the latter exhibits a weaker correlation (0.69) with its intra-molecular counterpart. In addition to the close similarity of intra- and inter-molecular solvent-mediated potentials, they are shown to be significantly mon residue-specific and thereby discriminative compared to the residue-mediated ones, indicating that solvent-mediation plays a major role in controlling the effective inter-residue interactions, either at interfaces, or within single monomers. Based on this observation, a reduced set of energy parameters comprising 20 one-body and 3 two-body terms is proposed (as opposed to the 20 x 20 tables of inter-residue potentials), which reproduces the conventional 20 x 20 tables with a correlation coefficient of 0.99.
Times Cited: 6
Source item page count: 9
Publication Date: DEC
IDS No.: 146CR
29-char source abbrev: PROTEIN SCI
Publisher address: 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA


Record 43 of 108
Author(s): Birol G; Doruker P; Kirdar B; Onsan ZI; Ulgen K
Title: Mathematical description of ethanol fermentation by immobilised Saccharomyces cerevisiae
Source: PROCESS BIOCHEMISTRY 1998, Vol 33, Iss 7, pp 763-771
Publisher: ELSEVIER SCI LTD
Addresses: Onsan ZI, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: Saccharomyces cerevisiae; ethanol fermentation; yeast growth; kinetic modelling; immobilisation
KeywordsPlus: CA-ALGINATE BEADS; ALCOHOLIC FERMENTATION; SUBSTRATE-INHIBITION; GROWTH; KINETICS; CELLS; YEAST; IMMOBILIZATION; GLUCOSE
Abstract: Fermentation characteristics of Saccharomyces cerevisiae ATCC 9763 immobilised in Ca-alginate gel beads have been investigated in a stirred batch system at 2, 4, 8, 10% (w/v) initial glucose concentrations. The experimental results were tested using eleven different kinetic models relating biomass and ethanol production and glucose utilisation in different forms. The models proposed by Monod and Hinshelwood were found to be more appropriate for describing the batch growth and ethanol production of immobilised S. cerevisiae at low (2-4%) and high (8-10%) initial glucose concentrations, respectively. The validation of the models chosen was done using data obtained from experiments in an inclined reactor with nutrient recirculation. (C) 1998 Elsevier Science Ltd. All rights reserved.
Times Cited: 0
Source item page count: 9
Publication Date: SEP
IDS No.: 139CU
29-char source abbrev: PROCESS BIOCHEM
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND


Record 44 of 108
Author(s): Lustig B; Bahar I; Jernigan RL
Title: RNA bulge entropies in the unbound state correlate with peptide binding strengths for HIV-1 and BIV TAR RNA because of improved conformational access
Source: NUCLEIC ACIDS RESEARCH 1998, Vol 26, Iss 22, pp 5212-5217
Publisher: OXFORD UNIV PRESS
Addresses: Lustig B, Appl Sci Consultants, 621-B River Oaks Pkwy, San Jose, CA 95134 USA
San Jose State Univ, Dept Chem, San Jose, CA 95192 USA
Appl Sci Consultants, San Jose, CA 95134 USA
Bogazici Univ, Ctr Polymer Res, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, TR-80815 Bebek, Istanbul, Turkey
NCI, Lab Expt & Computat Biol, Mol Struct Sect, NIH, Bethesda, MD 20892 USA
KeywordsPlus: MAJOR GROOVE; COMPLEX; RECOGNITION
Abstract: For the binding of peptides to wild-type HIV-1 and BIV TAR RNA and to mutants with bulges of various sizes, changes in the Delta Delta Gvalues of binding were determined from experimental K-d values. The corresponding entropies of these bulges are estimated by enumerating all possible RNA bulge conformations on a lattice and then applying the Boltzmann relationship. Independent calculations of entropies from fluctuations are also carried out using the Gaussian network model(GNM) recently introduced for analyzing folded structures. Strong correlations are seen between the changes in free energy determined for binding and the two different unbound entropy calculations. The fact that the calculated entropy increase with larger bulge size is correlated with the enhanced experimental binding free energy is unusual. This system exhibits a dependence on the entropy of the unbound form that is opposite to usual binding models. Instead of a large initial entropy being unfavorable since it would be reduced upon binding, here the larger entropies actually favor binding. Several interpretations are possible: (i) the higher conformational freedom implies a higher competence for binding with a minimal strain, by suitable selection amongst the set of already accessible conformations; (ii) larger bulge entropies enhance the probability of the specific favorable conformation of the bound state; (iii) the increased freedom of the larger bulges contributes more to the bound state than to the unbound state; (iv) indirectly the large entropy of the bound state might have an unfavorable effect on the solvent structure. Nonetheless, this unusual effect is interesting.
Times Cited: 3
Source item page count: 6
Publication Date: NOV 15
IDS No.: 140JV
29-char source abbrev: NUCL ACID RES
Publisher address: GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND


Record 45 of 108
Author(s): Baysal BM; Kayaman N
Title: Coil-globule transition of poly(methyl methacrylate) by intrinsic viscosity
Source: JOURNAL OF CHEMICAL PHYSICS 1998, Vol 109, Iss 19, pp 8701-8707
Publisher: AMER INST PHYSICS
Addresses: Baysal BM, Marmara Res Ctr, Dept Chem, POB 21, TR-41470 Gebze, Turkey
Marmara Res Ctr, Dept Chem, TR-41470 Gebze, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
KeywordsPlus: LINEAR POLYMER DIMENSIONS; THETA-TEMPERATURE; COLLAPSED REGIME; SINGLE-CHAIN; CYCLOHEXANE; POLYSTYRENE; MACROMOLECULES; KINETICS; POLY(ALPHA-METHYLSTYRENE); GYRATION
Abstract: The coil-globule transition for poly(methyl methacrylate) has been studied in the mixed solvent tert-butyl alcohol+water system. Two polymeric samples having molecular weights M-w=2.55 x 10(6) and M-w = 4.73 x 10(6) were used. The contraction and expansion of the molecular chains were determined by viscometric measurements, The results were compared with light scattering data obtained recently for the same system. A smooth and continuous contraction was observed below the theta temperature (41.5 degrees C). The temperature dependence of [eta] can be represented by a master curve in alpha(eta)(3)\tau\M-w(1/2) vs \tau\M-w(1/2) plot, where alpha(eta)(3) = [ eta(T)]/[ eta(theta)] is a viscosity expansion factor and tau =(T - theta)/T is the reduced temperature. A comparison of the observed globular radius with a theory for contracted coil confirmed the coil-globule transition for this system. (C) 1998 American Institute of Physics. [S0021-9606(98)52443-9].
Times Cited: 6
Source item page count: 7
Publication Date: NOV 15
IDS No.: 139AJ
29-char source abbrev: J CHEM PHYS
Publisher address: CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA



Record 46 of 108
Author(s): Dervisoglu M; Hortacsu O
Title: An experimental study of coal gasification
Source: ENERGY 1998, Vol 23, Iss 12, pp 1073-1076
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Addresses: Dervisoglu M, Bogazici Univ, Dept Chem Engn, PK 2, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Abstract: Experiments were carried out on a 2m diameter gas generator for a ceramics factory to study the effects of air-supply pressure, steam-saturation temperature and generator-gas exit temperature on fuel heating value. A total of 64 gasification experiments was performed using a standard coal mixture. Gaseous fuels with heating values ranging from 1100 to 1400 cal/liter were obtained. The heating value of the gas could be raised by up to 27% by maintaining the three process variables close to their optimum values, i.e. air-supply pressure = 43 cm of H2O, steam-saturation temperature = 55 degrees C, and generator gas-exit temperature = 160 degrees C. (C) 1998 Elsevier Science Ltd. All rights reserved.
Times Cited: 0
Source item page count: 4
Publication Date: DEC
IDS No.: 139FZ
29-char source abbrev: ENERGY
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND


Record 47 of 108
Author(s): Haliloglu T; Cho JH; Mattice WL
Title: Simulations of rotational isomeric state models for poly(propylene) melts on a high coordination lattice
Source: MACROMOLECULAR THEORY AND SIMULATIONS 1998, Vol 7, Iss 6, pp 613-617
Publisher: WILEY-V C H VERLAG GMBH
Addresses: Mattice WL, Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Bogazici Univ, Ctr Polymer Res, Istanbul, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, TR-80815 Bebek, Istanbul, Turkey
Dankook Univ, Dept Polymer Sci & Engn, Yongsan Gu, Seoul 140714, South Korea
Univ Akron, Maurice Morton Inst Polymer Sci, Akron, OH 44325 USA
KeywordsPlus: POLYETHYLENE CHAINS
Abstract: In the last two years, a method was developed for the Monte Carlo simulation of coarse-grained representations of the chains in polyethylene (PE) melts, under conditions where individual snapshots can be "reverse-mapped" back to continuous space, with all atoms present. In its original form, the symmetry of the torsion potential energy function, E(phi) = E(-phi), was exploited in the mapping of a coarse-grained version of the rotational isomeric state (RTS) model of PE onto a high coordination lattice. Recently the symmetry restriction was relaxed, so that the simulation could treat isolated RIS poly(propylene) (PP) chains of any stereochemical sequence. Here that simulation of isolated PP chains is extended to PP melts, by introducing the intermolecular interactions required for maintenance of cohesion with the proper cohesive energy. The method is applied to melts of isotactic PP and syndiotactic PP, and satisfactory cohesion is achieved. Satisfactory equilibration of the PP melts requires utilization of a reptation move, in addition to the single bead moves employed previously in simulations of PE melts.
Times Cited: 5
Source item page count: 5
Publication Date: NOV
IDS No.: 136ZE
29-char source abbrev: MACROMOL THEORY SIMUL
Publisher address: MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY


Record 48 of 108
Author(s): Erman B; Bahar I
Title: Local dynamics and glass transition
Source: MACROMOLECULAR SYMPOSIA 1998, Vol 133, pp 33-46
Publisher: WILEY-V C H VERLAG GMBH
Addresses: Erman B, Sabanci Univ, Sabanci Ctr, TR-80745 Istanbul, Turkey
Sabanci Univ, Sabanci Ctr, TR-80745 Istanbul, Turkey
Bogazici Univ, Ctr Polymer Res, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, TR-80815 Istanbul, Turkey
KeywordsPlus: FREELY ROTATING BONDS; MOLECULAR-DYNAMICS; POLYMER-CHAINS; CONFORMATIONAL DYNAMICS; RESTRICTIVE ENVIRONMENT; BULK POLYBUTADIENES; SINGLE-PARAMETER; DENSE MEDIA; RELAXATION; KINEMATICS
Abstract: The dynamics of polymer chains in the bulk state rue discussed at three different temperature scales: (i) Well above the glass transition temperature where the basic step of motion is the rotameric transition of bonds. In this regime, the dynamics may conveniently be analyzed by the rotational isomeric state model. (ii) In the vicinity of glass transition where friction forces from the environment dominate. In this regime, the dynamics may be modeled according to the cooperative kinematics model. (iii) Well below glass transition. Here, an analogy with a native protein is made, and the mean-squared fluctuations are analyzed by adopting the Gaussian Network Model, which recently proved successful in describing fluctuations in native proteins.
Times Cited: 3
Source item page count: 14
Publication Date: AUG
IDS No.: 133KJ
29-char source abbrev: MACROMOL SYMPOSIA
Publisher address: MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY


Record 49 of 108
Author(s): Ercan SN; Dervisoglu M
Title: Study of the steady flow behavior of hazelnut paste
Source: JOURNAL OF FOOD PROCESS ENGINEERING 1998, Vol 21, Iss 3, pp 181-190
Publisher: FOOD NUTRITION PRESS INC
Addresses: Dervisoglu M, Bogazici Univ, Kimyo Muh bol PK2, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
KeywordsPlus: RHEOLOGY
Abstract: The steady flow behavior of five different hazelnut pastes was studied and compared. Among the three steady shear geometries tried; cone and plate, plate and plate and concentric cylinder, the concentric cylinder was found to produce the most consistent data. Generated data were used to test the applicability of possible rheological models. Power Law Model could correlate the data very successfully. Yield stress values determined were quite low and application of Herschel-Bulkley Model did not improve the correlation significantly. The temperature dependency of the flow behavior was also studied obtaining data at four different temperatures. Correlations for temperature dependency were incorporated into the rheological model equations and these models were used to estimate pumping power requirements for pipe flow.
Times Cited: 0
Source item page count: 10
Publication Date: AUG
IDS No.: 123TX
29-char source abbrev: J FOOD PROCESS ENG
Publisher address: 6527 MAIN ST, P O BOX 374, TRUMBULL, CT 06611 USA


Record 50 of 108
Author(s): Bahar I; Jernigan RL
Title: Vibrational dynamics of transfer RNAs: Comparison of the free and synthetase-bound forms
Source: JOURNAL OF MOLECULAR BIOLOGY 1998, Vol 281, Iss 5, pp 871-884
Publisher: ACADEMIC PRESS LTD
Addresses: Jernigan RL, NCI, Mol Struct Sect, Lab Expt & Computat Biol, Div Basic Sci,NIH, Bethesda, MD 20892 USA
NCI, Mol Struct Sect, Lab Expt & Computat Biol, Div Basic Sci,NIH, Bethesda, MD 20892 USA
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Polymer Res Ctr, TR-80815 Bebek, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, TR-80815 Bebek, Turkey
Author Keywords: tRNA-synthetase complex; vibrational dynamics; recognition and binding; collective motions; B factors
KeywordsPlus: PHENYLALANINE TRANSFER-RNA; MOLECULAR-DYNAMICS; CRYSTALLOGRAPHIC REFINEMENT; RESTRAINED REFINEMENT; SINGLE-PARAMETER; STRUCTURAL BASIS; PROTEINS; RESOLUTION; MOTIONS; FLUCTUATIONS
Abstract: The vibrational dynamics of transfer RNAs, both free, and complexed with the cognate synthetase, are analyzed using a model (Gaussian network model) which recently proved to satisfactorily describe the collective motions of folded proteins. The approach is similar to a normal mode analysis, with the major simplification that no residue specificity is taken into consideration, which permits us (i) to cast the problem into an analytical form applicable to biomolecular systems including about 10(3) residues, and (ii) to acquire information on the essential dynamics of such large systems within computational times at least two orders of magnitude shorter than conventional simulations. On a local scale, the fluctuations calculated for yeast tRNA(Phe) and tRNA(Asp) in the free state, and for tRNA(Gln) complexed with glutaminyl-tRNA synthetase (GlnRS) are in good agreement with the corresponding crystallographic B factors. On a global scale, a hinge-bending region comprising nucleotides US to C12 in the D arm, G20 to G22 in the D loop, and m(7)G46 to C48 in the variable loop (for tRNA(Phe)), is identified in the free tRNA, conforming with previous observations. The two regions subject to the largest amplitude anticorrelated fluctuations in the free form, i.e. the anticodon region and the acceptor arm are, at the same time, the regions that experience the most severe suppression in their flexibilities upon binding to synthetase, suggesting that their sampling of the conformational space facilitates their recognition by the synthetase. Likewise, examination of the global mode of motion of GlnRS in the complex indicates that residues 40 to 45, 260 to 270, 306 to 314, 320 to 327 and 478 to 485, all of which cluster near the ATP binding site, form a hinge-bending region controlling the cooperative motion, and thereby the catalytic function, of the enzyme. The distal beta-barrel and the tRNA acceptor binding domain, on the other hand, are distinguished by their high mobilities in the global modes of motion, a feature typical of recognition sites, also observed for other proteins. Most of the conserved bases and residues of tRNA and GlnRS are severely constrained in the global motions of the molecules, suggesting their having a role in stabilizing and modulating the global motion. (C) 1998 Academic Press.
Times Cited: 11
Source item page count: 14
Publication Date: SEP 4
IDS No.: 117FX
29-char source abbrev: J MOL BIOL
Publisher address: 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND


Record 51 of 108
Author(s): Ozkan B; Bahar I
Title: Recognition of native structure from complete enumeration of low-resolution models with constraints
Source: PROTEINS-STRUCTURE FUNCTION AND GENETICS 1998, Vol 32, Iss 2, pp 211-222
Publisher: WILEY-LISS
Addresses: Bahar I, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Polymer Res Ctr, TR-80815 Bebek, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, Istanbul, Turkey
Author Keywords: sequential folding; local structure formation; coarsed-grained simulations; knowledge-based potentials; virtual bond rotations; misfolded structures
KeywordsPlus: PANCREATIC TRYPSIN-INHIBITOR; PROTEIN-STRUCTURE PREDICTION; AMIDE-PROTON-EXCHANGE; TERTIARY STRUCTURES; SECONDARY STRUCTURE; TERMINAL DOMAIN; X-RAY; MYOGLOBIN; ALGORITHM; POTENTIALS
Abstract: Complete sets of low-resolution conformations are generated for eight small proteins by rotating the C-alpha-C-alpha virtual bonds at selected flexible regions, while the remaining structural elements are assumed to move in rigid blocks. Several filtering criteria are used to reduce the ensemble size and to ensure the sampling of well-constructed conformations. These filters, based on structure and energy constraints deduced from knowledge-based studies, include the excluded volume requirement, the radius of gyration constraint, and the occurrence of sufficiently strong attractive inter-residue potentials to stabilize compact forms. About 8,000 well-constructed decoys or "probable folds" (PFs) are constructed for each protein. A correlation between root-mean-square (rms) deviations from X-ray structure and total energies is observed, revealing a decrease in energy as the rms deviation decreases, The conformation with the lowest energy exhibits an rms deviation smaller than 3.0 Angstrom in most of the proteins considered. The results are highly sensitive to the choice of flexible regions, A strong tendency to assume native state rotational angles is revealed for some flexible bonds from the analysis of the distributions of dihedral angles in the PFs, suggesting the formation of foldons near these locally stable regions at early folding pathway. Proteins 32:211-222, 1998, (C) 1998 Wiley-Liss, Inc.
Times Cited: 3
Source item page count: 12
Publication Date: AUG 1
IDS No.: 106KP
29-char source abbrev: PROTEIN-STRUCT FUNCT GENET
Publisher address: DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012 USA


Record 52 of 108
Author(s): Brega A; Scacchi R; Cuccia M; Kirdar B; Peloso G; Corbo RM
Title: Study of 15 protein polymorphisms in a sample of the Turkish population
Source: HUMAN BIOLOGY 1998, Vol 70, Iss 4, pp 715-728
Publisher: WAYNE STATE UNIV PRESS
Addresses: Brega A, Univ Milan, Dipartimento Biol & Genet Sci Med, Via Viotti 5, I-20133 Milan, Italy
Univ Milan, Dipartimento Biol & Genet Sci Med, I-20133 Milan, Italy
CNR, Ctr Genet Evoluz, Rome, Italy
Univ Pavia, Dipartimento Genet & Microbiol, I-27100 Pavia, Italy
Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Univ Pavia, Ist Med Legale, I-27100 Pavia, Italy
Univ La Sapienza, Dipartimento Genet & Biol Mol, Rome, Italy
Author Keywords: Turkish population; protein polymorphisms; multivariate analysis
KeywordsPlus: COAGULATION FACTOR-XIIIB; GENETIC-POLYMORPHISM; B-SUBUNIT; EUROPEAN POPULATIONS; JAPANESE POPULATION; OROSOMUCOID ORM1; GERMAN POPULATION; APOLIPOPROTEIN-E; C-II; ALLELE
Abstract: Anatolia, because of its geographic position and its use as an area of settlement, was also a land of transit that accommodated a succession of populations. The last important invasion occurred in the Middle Ages with the arrival of the Turks, an Altaic-speaking nomadic population descended from the Oguz tribes and originating in Mongolia. Although the Turks imposed their culture, their genetic contribution seems to have been modest. To validate this hypothesis, we studied the genetic structure of the Turkish population by examining 15 genetic markers in a sample of 93 subjects. The allele frequencies observed were HP*1 = 0.240; GLO1*1 = 0.344, ESD*2 = 0.134, GC*1S = 0.613, GC*1F = 0.129, PGM1*2S = 0.322, PGM1*2F = 0.041, PGM1*1F = 0.027, F13B*1 = 0.762, F13B*2 = 0.101, ORM1*S = 0.327, AHSG*2 = 0.181, C6*B = 0.239, C7*1 = 0.983, APOC2*1 = 1.0, APOE*3 = 0.868, APOE*2 = 0.063, BF*F = 0.258, BF*S07 = 0.017, BF*SQ0 = 0.011, C4A*Q0 = 0.145, C4A*2 = 0.070, C4A*5 = 0.012, C4A*6 = 0.023, C4B*Q0 = 0.101, C4B*2 = 0.048, C4B*3 = 0.005, and C4B*11 = 0.005. The present Turkish population was compared to other European, Middle Eastern, and North African populations by means of correspondence analysis. Turks cluster with Turkomans, who share the ancient Turks' derivation from the Oguz tribe. Moreover, Turks clearly belong to European groups and resemble the populations of neighboring countries. Therefore the present data support the hypothesis that the ancient Turkish tribes, who started to enter Anatolia 1000 years ago, contributed little to the gene pool of the preexisting Anatolian populations. Alternatively, if the genetic structure of the invading Turks resembled that of the ancient Anatolians, it will be impossible to find traces of their admixture with the autochthonous inhabitants of Anatolia. However, further analysis of other samples from Turkey and from populations living in the homelands of the Turkish tribes, namely, the eastern area of the Caspian Sea and Mongolia, is needed.
Times Cited: 6
Source item page count: 14
Publication Date: AUG
IDS No.: 107RQ
29-char source abbrev: HUM BIOL
Publisher address: 4809 WOODWARD AVE, DETROIT, MI 48201-1309 USA


Record 53 of 108
Author(s): Yildir C; Onsan ZI; Kirdar B
Title: Optimization of starting time and period of induction and inducer concentration in the production of the restriction enzyme EcoRI from recombinant Escherichia coli 294
Source: TURKISH JOURNAL OF CHEMISTRY 1998, Vol 22, Iss 3, pp 221-226
Publisher: SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY
Addresses: Yildir C, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: EcoRI; restriction enzyme; induction; enzyme purification
KeywordsPlus: PURIFICATION; ENDONUCLEASE; STRAIN; QUANTITIES
Abstract: Induction parameters including inducer concentration; period of induction and the cell concentration at which inducer is to be added to the fermentation broth were optimized in order to increase the yield of the EcoRI restriction endonuclease isolated from recombinant E. coli. Bacterial cells harboring the plasmid pPG430 containing EcoRI endonuclease and the methylase genes under the control of lac promoter were used in the experiments where induction was accomplished by using lactose isopropyl-beta-D-thiogalactoside (IPTG). An IPTG concentration of 0.1 mM, the late exponential phase of growth (at an optical density of 1.2 at 595 nm) and an induction period of 6 hours were determined to be the optimum conditions for induction.
Times Cited: 0
Source item page count: 6
IDS No.: 102CE
29-char source abbrev: TURK J CHEM
Publisher address: PO BOX 605 YENISEHIR, 06445 ANKARA, TURKEY


Record 54 of 108
Author(s): Isli AI; Aksoylu AE; Onsan ZI
Title: The effect of lanthanum and barium additives on the thermal stabilization of gamma-Al2O3
Source: TURKISH JOURNAL OF CHEMISTRY 1998, Vol 22, Iss 3, pp 253-260
Publisher: SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY
Addresses: Isli AI, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: gamma-Al2O3; thermal stabilization; lanthanum additive; barium additive; calcination
KeywordsPlus: TEMPERATURE CATALYTIC COMBUSTION; ALKALINE-EARTH IONS; SURFACE-AREA; RARE-EARTH; ALUMINA; METHANATION; SUPPORTS; NI/AL2O3
Abstract: The effect of La and Ba additives on the thermal stabilization of gamma-Al2O3 was investigated through total-surface-area measurements. The parameters considered were additive content, calcination temperature, and calcination period. The effect of precalcination was also studied. It was found that thermal stabilization caused by 3 wt% La and Ba is superior to 6 wt% La or Ba, and the positive effect of 3 wt% La and 3 wt% Ba are almost identical. The nearly threefold increase in the total surface area of 3 wt% La or Ba doped samples calcined above the gamma - alpha phase-transition temperature indicates that the aluminate complexes formed with La or Ba during phase transition impart thermal resistance to sintering. Aluminate formation at these temperatures is verified by XRD measurements. Precalcination at 723 K stabilizes the gamma-Al2O3 structure, leading to higher surface areas in the undoped sample upon sintering.
Times Cited: 0
Source item page count: 8
IDS No.: 102CE
29-char source abbrev: TURK J CHEM
Publisher address: PO BOX 605 YENISEHIR, 06445 ANKARA, TURKEY


Record 55 of 108
Author(s): Savas S; Gokgoz N; Kayserili H; Ozkinay F; Apak M; Kirdar B
Title: Deletion analysis of SMNtel, NAIP and BTF2p44tel genes in Turkish SMA families
Source: EUROPEAN JOURNAL OF HUMAN GENETICS 1998, Vol 6, pp P4145-
Publisher: STOCKTON PRESS
Addresses: Bogazici Univ, Dept Genet & Mol Biol, TR-80815 Bebek, Istanbul, Turkey
Istanbul Med Sch, Istanbul, Turkey
Ege Univ, Sch Med, Dept Genet & Teratol, Izmir, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Times Cited: 0
Source item page count: 1
Supplement: 1
IDS No.: ZX500
29-char source abbrev: EUR J HUMAN GENET
Publisher address: HOUNDMILLS, BASINGSTOKE RG21 6XS, HAMPSHIRE, ENGLAND


Record 56 of 108
Author(s): Onay T; Topaloglu O; Kayserili H; Camcioglu Y; Cokugras H; Akcakaya N; Apak M; Kirdar B
Title: Cystic fibrosis mutations and associated haplotypes in Turkey
Source: EUROPEAN JOURNAL OF HUMAN GENETICS 1998, Vol 6, pp P4158-
Publisher: STOCKTON PRESS
Addresses: Bogazici Univ, Dept Genet & Mol Biol, TR-80815 Bebek, Istanbul, Turkey
Istanbul Med Sch, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Times Cited: 0
Source item page count: 2
Supplement: 1
IDS No.: ZX500
29-char source abbrev: EUR J HUMAN GENET
Publisher address: HOUNDMILLS, BASINGSTOKE RG21 6XS, HAMPSHIRE, ENGLAND


Record 57 of 108
Author(s): Birol G; Onsan ZI; Kirdar B; Oliver SG
Title: Ethanol production and fermentation characteristics of recombinant Saccharomyces cerevisiae strains grown on starch
Source: ENZYME AND MICROBIAL TECHNOLOGY 1998, Vol 22, Iss 8, pp 672-677
Publisher: ELSEVIER SCIENCE INC
Addresses: Kirdar B, Bogazici Univ, Dept Chem Engn, Pk 2, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
UMIST, Dept Biochem & Appl Mol Biol, Manchester M60 1QD, Lancs, England
Author Keywords: recombinant yeast; starch; fermentation; alpha-amylase; glucoamylase
KeywordsPlus: ALPHA-AMYLASE; PLASMID STABILITY; EXPRESSION; GENE; CDNA
Abstract: The production of ethanol from starch has been investigated in three genetically modified Saccharomyces cerevisiae strains (YPG/AB, YPG/MM, and YPB-G). Two of the three strains produce the Aspergillus awamori glucoamylase together with either the Bacillus subtilis (YPG/AB) or the mouse (YPG/MM) alpha-amylase as separately secreted polypeptides. YPB-G, on the other hand, secretes a bifunctional fusion, protein that contains both the B. subtilis alpha-amylase and the A. awamori glucoamylase activities. Substrate utilization, biomass growth, and ethanol production were all studied in both starch- and glucose-containing media. Much higher growth rates were found when any of the three strains were grown on glucose. YPG/AB showed the most efficient utilization of starch for ethanol production with the lowest levels of reducing sugars accumulating in the medium. The superior performance of YPG/AB as compared to YPB-G was found to correlate with its higher level of alpha-amylase activity. The ethanol production levels of YPG/AB in starch- and glucose-containing media were found to be comparable. YPB-G, which secretes the bifunctional fusion protein, could produce ethanol in media with starch concentrations above 100 g l(-1) while YPG/M(M) over dot did not produce ethanol from starch because of its negligible secretion of glucoamylase. (C) 1998 Elsevier Science Inc.
Times Cited: 3
Source item page count: 6
Publication Date: JUN
IDS No.: ZU617
29-char source abbrev: ENZYME MICROB TECHNOL
Publisher address: 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA


Record 58 of 108
Author(s): Aksoylu AE; Onsan ZI
Title: Kinetics of CO hydrogenation over Ni-Mo/Al2O3 catalysts with and without K promotion
Source: INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 1998, Vol 37, Iss 6, pp 2397-2403
Publisher: AMER CHEMICAL SOC
Addresses: Onsan ZI, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
KeywordsPlus: METHANATION REACTION; CARBON-MONOXIDE; NICKEL; POTASSIUM; SUPPORT; MOLYBDENUM; NI/AL2O3; OLEFINS; SYNGAS
Abstract: The effect of K promotion on the CO hydrogenation activity and C-2-C-4 hydrocarbons selectivity of the 15 wt % Ni-10 wt % Mo/Al2O3 catalyst was investigated in the 498-548 K range using unpromoted and 1-3 wt % K-promoted samples. CO2 methanation tests at 523 K were used as a probe to confirm activity trends. Intrinsic kinetic data were obtained in the initial rate region on both unpromoted and 1 wt % K-promoted Ni-Mo catalysts. K promotion of the bimetallic Ni-Mo catalyst decreases both the activity and the specific activity of the Ni sites while increasing the C-2-C-3 olefin-to-paraffin ratio. The surface carbide mechanism with dissociative adsorption of hydrogen as the rate-limiting step gives the most plausible kinetic model among the models tested for both Ni-Mo and Ni-Mo-K catalysts.
Times Cited: 2
Source item page count: 7
Publication Date: JUN
IDS No.: ZT342
29-char source abbrev: IND ENG CHEM RES
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036 USA


Record 59 of 108
Author(s): Hamurcu EE; Akcelrud L; Baysal BM; Karasz FE
Title: Dynamic light scattering studies of poly(4-chlorostyrene) and poly(2-chlorostyrene) in theta solvents
Source: POLYMER 1998, Vol 39, Iss 16, pp 3657-3663
Publisher: ELSEVIER SCI LTD
Addresses: Baysal BM, TUBITAK, Marmara Res Ctr, Dept Chem, TR-41470 Gebze Kocaeli, Turkey
TUBITAK, Marmara Res Ctr, Dept Chem, TR-41470 Gebze Kocaeli, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Turkey
Univ Massachusetts, Dept Polymer Sci & Engn, Amherst, MA 01003 USA
Fed Univ Rio De Janeiro, Inst Quim, Rio De Janeiro, Brazil
Author Keywords: coil-globule transitions; dynamic tight scattering; halogenated polystyrenes
KeywordsPlus: LINEAR POLYMER DIMENSIONS; POLYSTYRENE-CYCLOHEXANE SYSTEM; TEMPERATURE-DEPENDENCE; INTRINSIC-VISCOSITY; GLOBULE TRANSITION; CHAIN; COLLAPSE; COIL; POLY(N-ISOPROPYLACRYLAMIDE); KINETICS
Abstract: Most studies of coil-to-globule transitions of macromolecules have dealt exclusively with the standard polystyrene-cyclohexane system. In this work we aim to extend such investigations to halogenated polystyrenes, namely poly(4-chlorostyrene)(PPCS), poly(2-chlorostyrene)(POCS) and poly(chlorostyrene)(PCS),a mixture of 2- and 4-isomers. Changes in R-h Of these polymers with temperature in their respective theta solvents were investigated by dynamic light scattering. The hydrodynamic size of PPCS in a-propyl benzene(M-W: 2.25 x 10(6) g mol(-1), M-W/M-n 1.16) decreases to 75% of that in the unperturbed state at 22.2 degrees C. POCS (M-W: 10.32 x 10(6) and M-W: 4.30 X 10(6), M-W/M-n: 1.10) in 2-butanone exhibited LCST behaviour and a Limited chain collapse was observed with increasing temperature above theta point. The parameters alpha(h) = R-h/R-h(theta) for POCS with two different molecular weights, (10.32 M and 4.30 M) were found to be 0.67 and 0.77, respectively at 37.0 degrees C. A smooth and continuous contraction was also observed for the mixture of 2- and 4-isomers, PCS (M-W: 2.32 x 10(6) g mol(-1), M-W/M-n: 1.06). (C) 1998 Elsevier Science Ltd. All rights reserved.
Times Cited: 1
Source item page count: 7
Publication Date: JUL
IDS No.: ZQ907
29-char source abbrev: POLYMER
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND


Record 60 of 108
Author(s): Ozkan L; Camurdan MC
Title: Model predictive control of a nonlinear unstable process
Source: COMPUTERS & CHEMICAL ENGINEERING 1998, Vol 22, pp S883-S886
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Addresses: Camurdan MC, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: dynamic matrix control; adaptive control; unstable process
Abstract: In this work, conventional (fixed model) dynamic matrix control (DMC), and adaptive (variable model) DMC which combines on-line parameter estimation via a recursive least squares algorithm and control are carried out on a nonlinear, unstable process. The controlled process has multiple steady states one of which is unstable. The control around the unstable point using DMC is done in a cascade arrangement. In the inner loop the unstable process is stabilized with an analog proportional only controller. This stabilized process is then controlled by the outer loop DMC. With this configuration stable control is achieved with the conventional DMC; whereas the stability and the performance of the system with the adaptive DMC is found to be dependent on the controller parameters. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
Times Cited: 1
Source item page count: 4
Supplement: S
IDS No.: ZL637
29-char source abbrev: COMPUT CHEM ENG
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND


Record 61 of 108
Author(s): Haliloglu T; Bahar I
Title: Coarse-grained simulations of conformational dynamics of proteins: Application to apomyoglobin
Source: PROTEINS-STRUCTURE FUNCTION AND GENETICS 1998, Vol 31, Iss 3, pp 271-281
Publisher: WILEY-LISS
Addresses: Bahar I, Bogazici Univ, Ctr Polymer Res, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Ctr Polymer Res, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, Bebek, Istanbul, Turkey
Author Keywords: low resolution models; knowledge-based potentials; unfolding kinetics; helix unwinding; cooperative motions; dynamic Monte Carlo; correlations between atomic fluctuations; virtual bond rotations
KeywordsPlus: KNOWLEDGE-BASED POTENTIALS; SPERM WHALE APOMYOGLOBIN; MONTE-CARLO SIMULATIONS; PROTON NMR-SPECTROSCOPY; LATTICE MODEL; NATIVE-STATE; COMPUTER-SIMULATION; X-RAY; INTERMEDIATE; PREDICTION
Abstract: A coarse-grained dynamic Monte Carlo method is proposed for investigating the conformational dynamics of proteins, Each residue is represented by two interaction sites, one at the alpha-carbon, and the other on the amino acid sidechain, Geometry and energy parameters extracted from databank structures are used, The method is applied to the crystal structure of apomyoglobin (apo-Mb). Equilibrium and dynamic properties of ape-Mb are characterized within computation times one order of magnitude shorter than conventional molecular dynamics (MD) simulations. The calculated rms fluctuations in alpha-carbons are in good agreement with crystallographic temperature factors. Regions exhibiting enhanced conformational mobilities are identified. Among the loops connecting the eight helices A to H, the loop CD undergoes the fastest motions, leading to partial unwinding of helix D. Helix G is the most stable helix on the basis of the kinetic stability of dihedral angles, followed by the respective helices A, E, H, and B. These results, in agreement with H/D exchange and two-dimensional NMR experiments, as well as with MD simulations, lend support to the use of the proposed approach as an efficient, yet physically plausible, means of characterizing protein conformational dynamics. (C) 1998 Wiley-Liss, Inc.
Times Cited: 8
Source item page count: 11
Publication Date: MAY 15
IDS No.: ZK813
29-char source abbrev: PROTEIN-STRUCT FUNCT GENET
Publisher address: DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012 USA


Record 62 of 108
Author(s): Kayaman N; Okay O; Baysal BM
Title: Swelling of polyacrylamide gels in polyacrylamide solutions
Source: JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS 1998, Vol 36, Iss 8, pp 1313-1320
Publisher: JOHN WILEY & SONS INC
Addresses: Okay O, TUBITAK, Marmara Res Ctr, Dept Chem, POB 21, TR-41470 Gebze, Kocaeli, Turkey
TUBITAK, Marmara Res Ctr, Dept Chem, TR-41470 Gebze, Kocaeli, Turkey
Kochi Univ, Dept Chem, TR-41300 Izmit, Kocaeli, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: swelling; polyacrylamide gels; swelling in polymer solutions; polymer-polymer interaction parameter
KeywordsPlus: RUBBER-ELASTICITY THEORY; POLYMER NETWORKS; POLY(ACRYLIC ACID); POLY(METHYL METHACRYLATE); BEHAVIOR; COMPLEXATION; COLLAPSE; EQUILIBRIUM; COPOLYMERIZATION; FLUORESCENCE
Abstract: Swelling behavior of polyacrylamide (PAAm) and polyacrylamide-co-polyacrylic acid (PAAm-co-PAAc) gels was investigated in aqueous solutions of monodisperse PAAms with molecular weights ((M) over bar(w)) ranging from 1.5 x 10(3) to 5 x 10(6) g/mol. The volume of the gels decreases as the PAAm concentration in the external solution increases. This decrease becomes more pronounced as the molecular weight of PAAm increases. The classical Flory-Huggins (FH) theory correctly predicts the swelling behavior of nonionic PAAm gels in PAAm solutions. The polymer-polymer interaction parameter chi(23) was found to decrease as the molecular weight of PAAm increases. The swelling behavior of PAAm-co-PAAc gels in PAAm solutions deviates from the predictions of the FH theory. This is probably due to the change of the ionization degree of AAc units depending on the polymer concentration in the external solution. (C) 1998 John Wiley & Sons, Inc.
Times Cited: 3
Source item page count: 8
Publication Date: JUN
IDS No.: ZK573
29-char source abbrev: J POLYM SCI B-POLYM PHYS
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012 USA


Record 63 of 108
Author(s): Haliloglu T; Mattice WL
Title: Mapping of rotational isomeric state chains with asymmetric torsional potential energy functions on a high coordination lattice: Application to polypropylene
Source: JOURNAL OF CHEMICAL PHYSICS 1998, Vol 108, Iss 16, pp 6989-6995
Publisher: AMER INST PHYSICS
Addresses: Haliloglu T, Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Bogazici Univ, Ctr Polymer Res, Istanbul, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, TR-80815 Istanbul, Turkey
Univ Akron, Inst Polymer Sci, Akron, OH 44325 USA
KeywordsPlus: DIELECTRIC-RELAXATION; POLYMERS; MODEL
Abstract: A high coordination lattice model was recently introduced for simulating coarse-grained rotational isomeric state (RIS) chains in which the bonds have symmetric torsional potential energy functions, E(phi) = E(-phi). This symmetry was exploited in the coarse-graining and mapping onto the high coordination lattice, thereby making the procedure unsuitable (without modification) for application to chains where one or more bonds has an asymmetric torsion potential energy function, E(phi) not equal E(-phi). The necessary modification is described here, and then documented by mapping previously described RIS models for isotactic and syndiotactic polypropylene onto the high coordination lattice. Each bead on the high coordination lattice represents a monomer unit, C3H6, of polypropylene. The conditional probabilities derived from the RIS model form the basis for the acceptance of the single bead moves used in the Monte Carlo simulations on the 2nnd lattice. The simulated chains have reasonable mean-square end-to-end distances and mean-square radii of gyration. The relaxation of the end-to-end vector follows the stretched exponential behavior, exp[-(t/tau)beta], where beta=0.5 and tau is the correlation time. The elaboration retains the ability to correctly treat chains in which the bonds have symmetric torsional potential energy functions, as shown by application to polyethylene, where each bead on the high coordination lattice represents C2H4. (C) 1998 American Institute of Physics.
Times Cited: 10
Source item page count: 7
Publication Date: APR 22
IDS No.: ZJ230
29-char source abbrev: J CHEM PHYS
Publisher address: CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA


Record 64 of 108
Author(s): Eroglu MS; Hazer B; Baysal BM
Title: Synthesis and thermal characterization of macromonomeric azo initiator containing poly(epsilon-caprolactone): Styrene and methyl methacrylate copolymerization
Source: JOURNAL OF APPLIED POLYMER SCIENCE 1998, Vol 68, Iss 7, pp 1149-1157
Publisher: JOHN WILEY & SONS INC
Addresses: Eroglu MS, TUBITAK Marmara Res Ctr, Dept Chem, POB 21, TR-41470 Gebze, Kocaeli, Turkey
TUBITAK Marmara Res Ctr, Dept Chem, TR-41470 Gebze, Kocaeli, Turkey
Zonguldak Karaelmas Univ, Dept Chem, TR-67100 Zonguldak, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Author Keywords: PCL; macroinitiator; crosslinked block copolymer; biodegradable copolymer
KeywordsPlus: BLOCK-COPOLYMERS; POLYCAPROLACTONE; POLYMERIZATION; AZOINITIATORS; MACRO
Abstract: Macromonomeric azo initiator containing biodegradable poly(epsilon-caprolactone, (PCL) was synthesized by the condensation reaction of PCL with 4,4'-azobis(4-cyanopentanoyl chloride) and methacryloyl chloride. This macromonomeric azo initiator (MIM-PCL) was further used in the polymerization of styrene (St) or methylmethacrylate (MMA) via a radical initiated process at 60 degrees C in bulk in order to obtain polystyrene (PS)-b-PCL or poly(methyl methacrylate) (PMMA)-b-PCL crosslinked block copolymers. Thermal decomposition kinetics of MIM-PCL and its copolymers were studied by using thermogravimetric analysis and differential scanning calorimetry (DSC). DSC traces of MIM-PCL showed two different exotherms, at 98 and 127 degrees C, The first exotherm, observed at 98 degrees C, was due to the polymerization of the terminal methacrylic groups; the other was due to the exothermic decomposition of azo groups of MIM-PCL. PCL-b-PS and PCL-b-PMMA crosslinked block copolymers showed single glass transition temperatures due to the compatibility of the crosslinked block segments. The polymer-solvent interaction parameter of PCL in chloroform was determined by vapor pressure osmometry to be 0.1 for the PCL-chloroform system at 30 degrees C. The average molecular weights between junction points of crosslinked homo PCL were calculated by using the Flory-Rehner equation. (C) 1998 John Wiley & Sons, Inc.
Times Cited: 1
Source item page count: 9
Publication Date: MAY 16
IDS No.: ZH689
29-char source abbrev: J APPL POLYM SCI
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012 USA


Record 65 of 108
Author(s): Aksoylu AE; Misirli Z; Onsan ZI
Title: Interaction between nickel and molybdenum in Ni-Mo/Al2O3 catalysts: I - CO2 methanation and SEM-TEM studies
Source: APPLIED CATALYSIS A-GENERAL 1998, Vol 168, Iss 2, pp 385-397
Publisher: ELSEVIER SCIENCE BV
Addresses: Onsan ZI, Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
TUBITAK, Marmara Res Ctr, Mat & Chem Technol Res Inst, TR-41470 Gebze, Kocaeli, Turkey
Author Keywords: nickel-alumina; nickel-molybdenum alumina; CO2 methanation; CO adsorption
KeywordsPlus: METAL-SUPPORT INTERACTIONS; ALUMINA CATALYSTS; HYDROGENATION
Abstract: A series of alumina supported Ni, Mo and Ni-Mo catalysts were prepared for investigating the interaction between Ni and Mo in terms of their structural properties and catalytic activities. The catalysts containing 0-15 wt% Ni and/or Mo were prepared by impregnation or coimpregnation and were tested for BET surface area and total pore volume. CO chemisorption was used for metal surface area measurements. The catalytic activities of the samples were tested by CO2 methanation. Selected Ni/Al2O3 and Ni-Mo/Al2O3 catalysts with Ni and Mo loadings in the 5-15 wt% range were also examined by TEM and SEM-EDX, The results show that Mo changes the structural properties and the methanation activities of the catalysts. TEM and SEM-EDX studies support the synergetic interaction between Ni sites and MoOx species and show that the nature of the Ni-Mo interaction changes with the level of Ni and Mo loading. At low Mo loadings, Mo species act as a diluent of the matrix, promoting Ni particle distribution. At higher Mo loadings, partial coverage of the nickel particles is observed especially on catalysts with high total metal loading. SEM backscattered composition images indicate the presence of molybdenum in the oxide form which means that the active sites are the nickel crystallites. (C) 1998 Elsevier Science B.V.
Times Cited: 6
Source item page count: 13
Publication Date: MAR 27
IDS No.: ZH652
29-char source abbrev: APPL CATAL A-GEN
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 66 of 108
Author(s): Aksoylu AE; Onsan ZI
Title: Interaction between nickel and molybdenum in Ni-Mo/Al2O3 catalysts: II - CO hydrogenation
Source: APPLIED CATALYSIS A-GENERAL 1998, Vol 168, Iss 2, pp 399-407
Publisher: ELSEVIER SCIENCE BV
Addresses: Onsan ZI, Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Author Keywords: nickel-alumina; nickel-molybdenum alumina; CO adsorption; CO hydrogenation
KeywordsPlus: METAL-SUPPORT INTERACTIONS; METHANATION; OLEFINS
Abstract: A series of alumina supported Ni, Mo and Ni-Mo catalysts prepared by impregnation or coimpregnation were tested to investigate the effects of Ni-Mo interaction on their structural properties and activity/selectivity characteristics in CO hydrogenation. The Ni and Mo contents of the catalysts were varied between 0-15 wt% according to a factorial experimental design. The results of CO hydrogenation tests reveal that the specific activity of the active sites changes with Mo loading, Ni:Mo molar ratio and total metal loading. Introducing Mo as the second metal increases the total hydrocarbon production as well as the C-2-C-4 hydrocarbons selectivity in the 498-573 K temperature range. Lower H-2/CO molar ratios increase C-2-C-4 selectivity, and this effect is enhanced with Mo addition especially to samples with higher Ni loading. (C) 1998 Elsevier Science B.V.
Times Cited: 3
Source item page count: 9
Publication Date: MAR 27
IDS No.: ZH652
29-char source abbrev: APPL CATAL A-GEN
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 67 of 108
Author(s): Eraslan S; Gokgoz N; Kirdar B
Title: Identification of deletion carriers in Duchenne/Becker muscular dystrophy families using a digoxigenin-labeled quantitative polymerase chain reaction technique
Source: MOLECULAR DIAGNOSIS 1997, Vol 2, Iss 4, pp 251-258
Publisher: CHURCHILL LIVINGSTONE INC MEDICAL PUBLISHERS
Addresses: Kirdar B, Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Mol Biol & Genet, TR-80815 Istanbul, Turkey
Author Keywords: dosage analysis; multiplex systems; computer-assisted laser densitometry; fluorescent primers
KeywordsPlus: GENE DELETIONS; DMD GENE; MUTATIONS; PCR; HYBRIDIZATION; FREQUENCY; PROTEIN; RNA; DNA
Abstract: Background: A quantitative polymerase chain reaction (PCR) technique based on the incorporation of digoxigenin (DIG), and visualization of the labeled fragments for the detection of deletion carriers in Duchenne/Becker muscular dystrophy families has been developed.

Methods and Results: Sixty-five DNA samples taken from mothers and/or sisters of familial and sporadic deletion patients were investigated in the exponential phase of amplification. All obligate carriers were correctly identified using this technique. In more than 95% of deletion families. possible carriers could be screened by using four different multiplex systems specifically designed to increase the efficiency of the detection. Deletions were found to be present in 42% of possible carriers. All these results were confirmed by computer-assisted laser densitometry.

Conclusion: Dosage analysis by DIG-labeled quantitative PCR is a reliable and accurate technique for detecting Duchenne/Becker muscular dystrophy deletion carriers.

Times Cited: 0
Source item page count: 8
Publication Date: DEC
IDS No.: ZF450
29-char source abbrev: MOL DIAGN
Publisher address: CURTIS CENTER, INDEPENDENCE SQUARE WEST, PHILADELPHIA, PA 19106-3399 USA


Record 68 of 108
Author(s): Onay T; Topaloglu O; Zielenski J; Gokgoz N; Kayserili H; Camcioglu Y; Cokugras H; Akcakaya N; Apak M; Tsui LC; Kirdar B
Title: Analysis of the CFTR gene in Turkish cystic fibrosis patients: identification of three novel mutations (3172delAC, P1013L and M1028I)
Source: HUMAN GENETICS 1998, Vol 102, Iss 2, pp 224-230
Publisher: SPRINGER VERLAG
Addresses: Kirdar B, Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Genet & Mol Biol, TR-80815 Istanbul, Turkey
Hosp Sick Children, Dept Genet, Toronto, ON M5G 1X8, Canada
Istanbul Univ, Inst Child Hlth, Div Med Genet, Istanbul, Turkey
Istanbul Univ, Cerrahpasa Med Sch, Dept Pediat, Istanbul, Turkey
KeywordsPlus: TRANSMEMBRANE CONDUCTANCE REGULATOR; NONSENSE MUTATION; POPULATION; CHROMOSOMES; FREQUENCY; DELETION; DNA; POLYMORPHISM; HAPLOTYPES; EXPRESSION
Abstract: In order to determine the spectrum of cystic fibrosis (CF) mutations In the Turkish population, a complete coding region of the cystic fibrosis transmembrane conductance regulator (CFTR) gene including exon-intron boundaries, on 122 unrelated CF chromosomes from 73 Turkish CF families was analysed by denaturing gradient gel electrophoresis and multiplex heteroduplex analysis on MDE gel matrix. in addition to 15 previously reported mutations and 12 polymorphisms, three novel mutations, namely 3172delAC, P1013L and M1028I, were detected. Delta F508 was found to be present on 18.8% of CF chromosomes. The second most common mutation was 1677delTA, with a frequency of 7.3%, followed by G542X and 2183AA-->G mutations, with frequencies of 4.9%. These four most common mutations in Turkish CF population account for approximately 36% of mutations. This study could only detect 52.5% of disease-causing mutations in this population; 47.5% of CF alleles remain to be identified, reflecting the high molecular heterogeneity of the Turkish population.
Times Cited: 6
Source item page count: 7
Publication Date: FEB
IDS No.: ZB303
29-char source abbrev: HUM GENET
Publisher address: 175 FIFTH AVE, NEW YORK, NY 10010 USA

Record 69 of 108
Author(s): Aksoylu AE; Onsan ZI
Title: A parametric study on CO2 hydrogenation by Ni-based monometallic and bimetallic catalysts
Source: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 1998, Vol 215, pp 214-COLL-
Publisher: AMER CHEMICAL SOC
Addresses: Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Times Cited: 0
Source item page count: 1
Publication Date: APR 2
Part number: 1
IDS No.: ZA911
29-char source abbrev: ABSTR PAP AMER CHEM SOC
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036 USA


Record 70 of 108
Author(s): Haliloglu T; Cho JH; Mattice W
Title: Simulation of rotational isomeric state models for polypropylene melts on a high coordination lattice
Source: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 1998, Vol 215, pp 197-PMSE-
Publisher: AMER CHEMICAL SOC
Addresses: Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Bogazici Univ, Polymer Res Ctr, Istanbul, Turkey
Dankook Univ, Dept Polymer Sci & Polymer Engn, Seoul, South Korea
Univ Akron, Maurice Morton Inst Polymer Sci, Akron, OH 44325 USA
Times Cited: 0
Source item page count: 1
Publication Date: APR 2
Part number: 2
IDS No.: ZA912
29-char source abbrev: ABSTR PAP AMER CHEM SOC
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036 USA


Record 71 of 108
Author(s): Baysal B; Erbil C; Morganelli PL; Stockmayer WH
Title: Dielectric studies of various olefin/SO2 copolymers
Source: TURKISH JOURNAL OF CHEMISTRY 1997, Vol 21, Iss 4, pp 239-245
Publisher: SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY
Addresses: Baysal B, Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, Istanbul, Turkey
Tubitak Marmara Res Ctr, Gebze, Kocaeli, Turkey
Istanbul Tech Univ, Dept Chem, TR-80626 Istanbul, Turkey
Dartmouth Coll, Dept Chem, Hanover, NH 03755 USA
KeywordsPlus: TERPOLYMERS; SULFONES); DYNAMICS
Abstract: Dielectric constant and loss have been measured at low and high frequencies for several poly(1-olefin sulfones) as well as for the polysulfones of allybenzene and allyl cyclopentane. The low-frequency dispersion in allylbenzene due to helical sequences is weaker in benzene than in dioxane, and in both solvents is much lower than for the l-olefin polymers. Solvent effects on the high frequency process are also reported, but yield no simple uniform picture.
Times Cited: 1
Source item page count: 7
IDS No.: ZA085
29-char source abbrev: TURK J CHEM
Publisher address: PO BOX 605 YENISEHIR, 06445 ANKARA, TURKEY


Record 72 of 108
Author(s): Bahar I; Wallqvist A; Covell DG; Jernigan RL
Title: Correlation between native-state hydrogen exchange and cooperative residue fluctuations from a simple model
Source: BIOCHEMISTRY 1998, Vol 37, Iss 4, pp 1067-1075
Publisher: AMER CHEMICAL SOC
Addresses: Jernigan RL, NCI, Div Basic Sci, Mol Struct Sect, Lab Expt & Computat Biol,Div Basic Sci,NIH, Bethesda, MD 20892 USA
NCI, Div Basic Sci, Mol Struct Sect, Lab Expt & Computat Biol,Div Basic Sci,NIH, Bethesda, MD 20892 USA
Bogazici Univ, Polymer Res Ctr, TR-80815 Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
TUBITAK, Adv Polymer Mat Res Ctr, TR-80815 Istanbul, Turkey
NCI, Frederick Canc Res & Dev Ctr, Sci Applicat Int Corp, Frederick, MD 21702 USA
KeywordsPlus: PANCREATIC TRYPSIN-INHIBITOR; NUCLEAR MAGNETIC-RESONANCE; FRENCH BEAN PLASTOCYANIN; AMIDE-PROTON-EXCHANGE; COLI RIBONUCLEASE HI; CYTOCHROME-C; STAPHYLOCOCCAL NUCLEASE; CIRCULAR-DICHROISM; CRYSTAL-STRUCTURE; ESCHERICHIA-COLI
Abstract: Recently, we developed a simple analytical model based on local residue packing densities and the distribution of tertiary contacts for describing the conformational fluctuations of proteins in their folded state. This so-called Gaussian network model (GNM) is applied here to the interpretation of experimental hydrogen exchange (HX) behavior of proteins in their native state or under weakly denaturing conditions. Calculations are performed for five proteins: bovine pancreatic trypsin inhibitor, cytochrome c, plastocyanin, staphylococcal nuclease, and ribonuclease H. The results are significant in two respects, First, a good agreement is reached between calculated fluctuations and experimental measurements of HX despite the simplicity of the model and within computational times 2 or 3 orders of magnitude faster than earlier, more complex simulations. Second, the success of a theory, based on the coupled conformational fluctuations of residues near the native state, to satisfactorily describe the native-state HX behavior indicates the significant contribution of local, but cooperative, fluctuations to protein conformational dynamics. The correlation between the HX data and the unfolding kinetics of individual residues further suggests that local conformational susceptibilities as revealed by the GNM approach may have implications relevant to the global dynamics of proteins.
Times Cited: 27
Source item page count: 9
Publication Date: JAN 27
IDS No.: YV442
29-char source abbrev: BIOCHEMISTRY-USA
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036 USA


Record 73 of 108
Author(s): Kayaman N; Kazan D; Erarslan A; Okay O; Baysal BM
Title: Structure and protein separation efficiency of poly(N-isopropylacrylamide) gels: Effect of synthesis conditions
Source: JOURNAL OF APPLIED POLYMER SCIENCE 1998, Vol 67, Iss 5, pp 805-814
Publisher: JOHN WILEY & SONS INC
Addresses: Okay O, Tubitak Marmara Res Ctr, Res Inst Basic Sci, POB 21, TR-41470 Gebze, Kocaeli, Turkey
Tubitak Marmara Res Ctr, Res Inst Basic Sci, TR-41470 Gebze, Kocaeli, Turkey
Tubitak Marmara Res Ctr, Res Inst Genet Engn & Biotechnol, TR-41470 Gebze, Kocaeli, Turkey
Kocaeli Univ, Fac Arts & Sci, Dept Chem, TR-41300 Izmit, Kocaeli, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Istanbul, Turkey
Author Keywords: poly(N-isopropylacrylamide); temperature-sensitive gels; gel swelling; protein separation efficiency; gel extraction
KeywordsPlus: TEMPERATURE-SENSITIVE HYDROGEL; PHASE-TRANSITION; POLYACRYLAMIDE GELS; POLYMER NETWORKS; SALT-SOLUTIONS; COLLAPSE; WATER; CYCLIZATION; EXTRACTION; ASSAY
Abstract: Crosslinked poly(N-isopropylacrylamide) (PNIPA) gels with different crosslink densities in the form of rods and beads were prepared by free-radical crosslinking copolymerization. Solution and inverse suspension polymerization techniques were used for the gel synthesis. The gels were utilized to concentrate dilute aqueous solutions of penicillin G acylase (PGA), bovine serum albumin (BSA), and 6-aminopenicillanic acid (6-APA). The discontinuous volume transition at 34 degrees C observed in the gel swelling was used as the basis of concentrating dilute aqueous protein solutions. PNIPA gels formed below 18 degrees C were homogeneous, whereas those formed at higher temperatures exhibited heterogeneous structures. The water absorption capacity of PNIPA gels in the form of beads was much higher, and their rate of swelling was much faster than the rod-shaped PNIPA gels. It was also found that the polymerization techniques used significantly affect the properties of PNIPA gels. The separation efficiency decreased when the protein molecules PGA or BSA in the external solution were replaced with small-molecular-weight compounds, such as 6-APA. The protein separation efficiency by the gel beads increased to 100% after coating the bead surfaces with BSA. (C) 1998 John Wiley & Sons, Inc.
Times Cited: 20
Source item page count: 10
Publication Date: JAN 31
IDS No.: YQ699
29-char source abbrev: J APPL POLYM SCI
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012 USA


Record 74 of 108
Author(s): Ozyurt B; Sunol AK; Camurdan MC; Mogili P; Hall LO
Title: Chemical plant fault diagnosis through a hybrid symbolic-connectionist machine learning approach
Source: COMPUTERS & CHEMICAL ENGINEERING 1998, Vol 22, Iss 1-2, pp 299-321
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Addresses: Sunol AK, Univ S Florida, Coll Engn, Tampa, FL 33620 USA
Univ S Florida, Coll Engn, Tampa, FL 33620 USA
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
KeywordsPlus: ARTIFICIAL NEURAL NETWORKS; DECISION TREES; KNOWLEDGE; SYSTEM; MODEL
Abstract: A novel hybrid symbolic-connectionist approach to machine learning is introduced and applied to fault diagnosis of a hydrocarbon chlorination plant. The learning algorithm addresses the knowledge acquisition problem by developing and maintaining the knowledge base through instance based inductive learning. The performance of the learning system is discussed in terms of the knowledge extracted from example cases and its classification accuracy on the test cases. Results indicate that the introduced system is a promising alternative to neural networks for fault diagnosis and a complement to expert systems. (C) 1997 Elsevier Science Ltd.
Times Cited: 1
Source item page count: 23
IDS No.: YM359
29-char source abbrev: COMPUT CHEM ENG
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND


Record 75 of 108
Author(s): Aksoylu AE; Onsan ZI
Title: Hydrogenation of carbon oxides using coprecipitated and impregnated Ni/Al2O3 catalysts
Source: APPLIED CATALYSIS A-GENERAL 1997, Vol 164, Iss 1-2, pp 1-11
Publisher: ELSEVIER SCIENCE BV
Addresses: Onsan ZI, Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Bogazici Univ, Dept Chem Engn, TR-80815 Bebek, Istanbul, Turkey
Author Keywords: nickel-alumina; coprecipitation; impregnation; CO hydrogenation; CO2 methanation
KeywordsPlus: NICKEL-ALUMINA CATALYSTS; METHANATION; CO2; CONVERSION; ADSORPTION; METALS; COBALT
Abstract: A group of Ni/Al2O3 catalysts having metal contents in the 0-16.5 wt% range were prepared using coprecipitation and impregnation methods. The catalysts were reduced under the same conditions; the reaction conditions were also fixed in similar sets of experiments for better comparison, Total surface area, total pore volume, metal surface area, and both the CO hydrogenation and CO2 methanation activities of the catalysts were studied in order to compare the effect of preparation method on structural properties as well as on catalyst activity and selectivity. A comparison of CO hydrogenation results on catalysts with similar nickel loadings indicates that coprecipitated catalysts have higher productivity and C-2-C-4 hydrocarbon selectivity, whereas impregnated catalysts yield better olefin/paraffin ratios for the C-2-C-3 hydrocarbons. In CO2 methanation, coprecipitated catalysts show higher methanation activity and lower CO production level per methane produced for all nickel loadings investigated. (C) 1997 Elsevier Science B.V.
Times Cited: 7
Source item page count: 11
Publication Date: DEC 23
IDS No.: YL761
29-char source abbrev: APPL CATAL A-GEN
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 76 of 108
Author(s): Akin AN; Onsan ZI
Title: Kinetics of CO hydrogenation over coprecipitated cobalt-alumina
Source: JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY 1997, Vol 70, Iss 3, pp 304-310
Publisher: JOHN WILEY & SONS LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
Author Keywords: coprecipitation; cobalt-alumina; CO hydrogenation; intrinsic kinetics
KeywordsPlus: FISCHER-TROPSCH SYNTHESIS; CATALYTIC SYNTHESIS; METHANATION REACTION; CARBON-MONOXIDE; HYDROCARBONS; SELECTIVITY; METALS
Abstract: The kinetics of CO hydrogenation over coprecipitated 36 wt% Co/Al2O3 was studied in a fixed-bed microreactor at atmospheric pressure. Intrinsic kinetic data were obtained in the initial rate region using four different CO concentrations and two different H-2/CO ratios over the 473-523 K temperature range. The surface carbide mechanism. with dissociative adsorption of hydrogen as the rate controlling step gives the most plausible kinetic model among the eight different models tested. C-1-C-4 production rates are found to be strongly influenced by temperature, and optimum C-1-C-4 hydrocarbon selectivity is obtained at 508 K. The activation energy for CO consumption and CH4 formation are calculated as 74 +/- 2 kJ mol(-1) and 84 +/- 2 kJ mol(-1) respectively.
Times Cited: 3
Source item page count: 7
Publication Date: NOV
IDS No.: YF723
29-char source abbrev: J CHEM TECHNOL BIOTECHNOL
Publisher address: BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD


Record 77 of 108
Author(s): Kayaman N; Okay O; Baysal BM
Title: Swelling of polyacrylamide gels in aqueous solutions of ethylene glycol oligomers
Source: POLYMER GELS AND NETWORKS 1997, Vol 5, Iss 4, pp 339-356
Publisher: ELSEVIER SCI LTD
Addresses: TUBITAK,MARMARA RES CTR,RES INST BASIC SCI,DEPT CHEM,TR-41470 GEBZE,KOCAELI,TURKEY
KOCAELI UNIV,DEPT CHEM,TR-41300 IZMIR,KOCAELI,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
KeywordsPlus: PHASE-TRANSITION; POLYMER NETWORKS; COLLAPSE; BEHAVIOR
Abstract: Addition of a small amount of ethylene glycol oligomers (OEG), with the number of repeat units y = 2-4, in an aqueous solution leads to the contraction of both linear and cross-linked poly(acrylamide-co-acrylic acid) chains. The results present clear evidence for the screening Effect of OEG on the ionic groups of the polymer chains. Measurements indicate that the pre-swollen poly(acrylamide-co-acrylic acid) gels immersed in aqueous OEG solutions are at equilibrium. However, as the molecular weight of OEG increases, these gels cannot attain their equilibrium swelling ratio due to the appearance of non-equilibrium structures. The stability of these structures increases as the initial swelling degree of the gels increases. (C) 1997 Elsevier Science Ltd.
Times Cited: 8
Source item page count: 18
IDS No.: YF382
29-char source abbrev: POLYM GELS NETWORKS
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 78 of 108
Author(s): Bahar I; Kaplan M; Jernigan RL
Title: Short-range conformational energies, secondary structure propensities, and recognition of correct sequence-structure matches
Source: PROTEINS-STRUCTURE FUNCTION AND GENETICS 1997, Vol 29, Iss 3, pp 292-308
Publisher: WILEY-LISS
Addresses: NCI,MOL STRUCT SECT,MATH BIOL LAB,DIV BASIC SCI,NIH,BETHESDA,MD 20892
BOGAZICI UNIV,CTR POLYMER RES,TR-80815 BEBEK,ISTANBUL,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
TUBITAK,ADV POLYMER MAT RES CTR,TR-80815 BEBEK,ISTANBUL,TURKEY
Author Keywords: knowledge-based potentials; virtual bonds; coupling between bond torsions and bond angles; secondary structure propensities; inverse folding experiments
KeywordsPlus: HELIX-FORMING TENDENCIES; ALPHA-HELIX; AMINO-ACIDS; THERMODYNAMIC SCALE; GLOBULAR PROTEINS; PACKING DENSITY; POTENTIALS; STABILITY; REPRESENTATION; PREDICTION
Abstract: A statistical analysis of known structures is made for an assessment of the utility of short-range energy considerations. For each type of amino acid, the potentials governing (1) the torsions and bond angle changes of virtual C-alpha-C-alpha bonds and (2) the coupling between torsion and bond angle changes are derived. These contribute approximately -2 RT per residue to the stability of native proteins, approximately half of which is due to coupling effects. The torsional potentials for the alpha-helical states of different residues are verified to be strongly correlated with the free-energy change measurements made upon single-site mutations at solvent-exposed regions, Likewise, a satisfactory correlation is shown between the beta-sheet potentials of different amino acids and the scales from free-energy measurements, despite the role of tertiary context in stabilizing beta-sheets. Furthermore, there is excellent agreement between our residue-specific potentials for alpha-helical state and other thermodynamic based scales. Threading experiments performed by using an inverse folding protocol show that 50 of 62 test structures correctly recognize their native sequence on the basis of short-range potentials. The performance is improved to 55, upon simultaneous consideration of short-range potentials and the nonbonded interaction potentials between sequentially distant residues, Interactions between near residues along the primary structure, i.e., the local or short-range interactions, are known to be insufficient, alone, for understanding the tertiary structural preferences of proteins alone. Yet, knowledge of short-range conformational potentials permits rationalizing the secondary structure propensities and aids in the discrimination between correct and incorrect tertiary folds. (C) 1997 Wiley-Liss, Inc.
Times Cited: 13
Source item page count: 17
Publication Date: NOV
IDS No.: YE223
29-char source abbrev: PROTEIN-STRUCT FUNCT GENET
Publisher address: DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012


Record 79 of 108
Author(s): Karal O; Hamurcu EE; Baysal BM
Title: Blends of polycaprolactone-poly(dimethylsiloxane)-polycaprolactone triblock copolymer with poly(vinyl chloride): preparation and characterization
Source: POLYMER 1997, Vol 38, Iss 24, pp 6071-6078
Publisher: ELSEVIER SCI LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
TUBITAK,MARMARA RES CTR,DEPT CHEM,TR-41470 GEBZE,KOCAELI,TURKEY
Author Keywords: polycaprolactone; poly(dimethylsiloxane); polycaprolactone; poly(vinyl chloride); miscibility
KeywordsPlus: POLYMER BLENDS; GAS PERMEATION; PVC COMPOUNDS; POLYVINYL-CHLORIDE); MORPHOLOGY; SURFACE
Abstract: Miscibility, thermal, mechanical, gas permeation, morphological and surface properties of poly(vinyl chloride) (PVC) blends containing 1-10% triblock polycaprolactone-poly(dimethylsiloxane)-polycaprolactone (PCL-PDMS-PCL) copolymer were investigated by using several techniques. Fourier transform infra-red analysis of blends reveal the existence of specific interactions via hydrogen bonding between the alpha-hydrogen of PVC and the carbonyl group of PCL in the triblock copolymer. This PCL-PDMS-PCL/PVC blend system exhibited a single glass transition according to differential scanning calorimetry and dynamic mechanical thermal analysis results. Stress-strain results showed that PCL-PDMS-PCL triblock copolymer is a very effective plasticizer for PVC. Gas permeability of the blends increased with the copolymer content. Morphological and surface properties of the blend system were examined by scanning electron microscopy and contact angle measurements. (C) 1997 Elsevier Science Ltd.
Times Cited: 3
Source item page count: 8
Publication Date: NOV
IDS No.: YC404
29-char source abbrev: POLYMER
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 80 of 108
Author(s): Erbil HY; Yasar B; Suzer S; Baysal BM
Title: Surface characterization of the hydroxy-terminated poly(epsilon-caprolactone)/poly(dimethylsiloxane) triblock copolymers by electron spectroscopy for chemical analysis and contact angle measurements
Source: LANGMUIR 1997, Vol 13, Iss 20, pp 5484-5493
Publisher: AMER CHEMICAL SOC
Addresses: Erbil HY, TUBITAK,DEPT CHEM,MARMARA RES CTR,POB 21,TR-41470 GEBZE,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,TURKEY
BILKENT UNIV,DEPT CHEM,TR-06533 BILKENT,TURKEY
KeywordsPlus: BLOCK-COPOLYMERS; POLYMER SURFACE; SPREADING PRESSURE; POLYSILOXANE; POLYETHYLENE; POLYSTYRENE; WETTABILITY; WATER; BULK
Abstract: The surface composition and free energy properties of two grades of amphiphilic and semicrystalline triblock copolymers consisting of a poly(dimethylsiloxane) (PDMS) midblock (M-w similar to 2300) coupled to poly(epsilon-caprolactone) (PCL) end blocks having differing molecular weights (M-w similar to 2000, sample P3, and M-w similar to 3000, sample P2) and homopolymer PCL (M-w similar to 40 000) were investigated by Fourier transform infrared, spectroscopy, electron spectroscopy for chemical analysis (ESCA), and contact angle measurements using critical surface tension, one-liquid and two-liquid methods. ESCA showed that the molar concentration of PDMS increased from 36.5% in the bulk up to 70.2% in the surface for sample P2 and from 46.3% in the bulk up to 79.2% in the surface for sample P3 in high vacuum. This indicates that the lower surface energy PDMS microdomains were segregated in the surface region to minimize the surface energy of the copolymer. The longer the PCL block, the higher the phase separation. One-liquid contact angle results were evaluated by using van Oss, Good, and Chaudhury's Lifshitz-van der Waals and Lewis acid-base (AB) methodology, and it was determined that the basicity surface tension coefficients (gamma(s)(-)) of the copolymers decreased with the increase of the PDMS content at the surface, a result in agreement with the ESCA results but not proportional to them, indicating that the surfaces of the copolymers are highly mobile and molecular rearrangement takes place upon contacting with a polar testing liquid drop. The strong AB interaction between the basic carboxyl groups of PCL segments with the Lewis acidic groups of the polar liquids restructured the surface molecular composition at the contact area by increasing PCL and decreasing PDMS concentration in polar environments. The two-liquid contact angle method was also applied, and it was determined that gamma(s)(-) decreased inverse proportionally with the increase of PDMS segments. Also, it was realized that the molecular restructuring did not take place in the two-liquid method.
Times Cited: 8
Source item page count: 10
Publication Date: OCT 1
IDS No.: XZ089
29-char source abbrev: LANGMUIR
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036


Record 81 of 108
Author(s): Bahar I
Title: Local relaxation of polymers in dense media: Cooperative kinematics theory and applications
Source: MACROMOLECULAR THEORY AND SIMULATIONS 1997, Vol 6, Iss 5, pp 881-906
Publisher: HUTHIG & WEPF VERLAG
Addresses: Bahar I, BOGAZICI UNIV,CTR POLYMER RES,TR-80815 BEBEK,ISTANBUL,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
TUBITAK,ADV POLYMER MAT RES CTR,TR-80815 BEBEK,ISTANBUL,TURKEY
KeywordsPlus: MOLECULAR-DYNAMICS SIMULATION; BULK AMORPHOUS POLYMERS; FREELY ROTATING BONDS; CONFORMATIONAL TRANSITIONS; BROWNIAN DYNAMICS; GLASS-TRANSITION; CHAIN MOLECULES; ORIENTATIONAL CORRELATIONS; RESTRICTIVE ENVIRONMENT; COMPUTER-SIMULATIONS
Abstract: Cooperative kinematics (CK) theory and its recent applications are presented. CK theory has been developed as an efficient approach for predicting the mechanism of segmental relaxation processes in bulk polymers. The theory aims at determining the most probable changes in atomic coordinates, occurring collectively in response to a given, external or localized, structural perturbation. The basic postulate is the minimization of the energy change involved in the overall conformational motion, which naturally yields the optimal pathway of cooperative relaxation. Attention has been confined here to the collective motions accompanying the rotational transitions of backbone bonds in polyethylene (PE) and polybutadiene (PB). The strong dependence of the mechanism of motions on the geometry of the repeat unit and on chain connectivity is emphasized. The differences in the types of correlated transitions operating in different structures, the effective conformational energy changes triggered by bond rotational jumps, and the correlation lengths for particular bond isomerizations are analyzed. The reorientations of C-H bond vectors in cis- and trans-PB are also examined to explain the shorter correlation time of cia units, compared to trans, detected by NMR. A good agreement between various CK predictions and results from molecular dynamics (MD) simulations is obtained. The fact that CK calculations are at least two orders of magnitude faster than MD simulations invites attention to the utility of the CK method as an efficient tool for elucidating the pathway of motion in complex systems.
Times Cited: 3
Source item page count: 26
Publication Date: SEP
IDS No.: XW911
29-char source abbrev: MACROMOL THEORY SIMUL
Publisher address: AUF DEM WOLF 4, CH-4052 BASEL, SWITZERLAND


Record 82 of 108
Author(s): Cvetkovska M; Lazarevic M; Koseva S; Baysal B; Hamurcu EE; Uyanik N
Title: Macro-azo-initiators having poly(ethylene glycol) units: Synthesis, characterization, and application to AB block copolymerization
Source: JOURNAL OF APPLIED POLYMER SCIENCE 1997, Vol 65, Iss 11, pp 2173-2181
Publisher: JOHN WILEY & SONS INC
Addresses: TUBITAK MARMARA RES CTR,DEPT CHEM,TR-41470 GEBZE,TURKEY
SV KIRIL & METODIJ UNIV,FAC TECHNOL & MET,SKOPJE,MACEDONIA
BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,TURKEY
ISTANBUL TECH UNIV,DEPT CHEM,TR-80626 MASLAK,ISTANBUL,TURKEY
KeywordsPlus: THERMAL-PROPERTIES; POLYMERIZATION; STYRENE
Abstract: Macro-azo-initiators (MAIs) having poly( ethylene glycol)(PEG) units were obtained by various multistep synthetic approaches. In the first stage, macro-azo-initiators of PEG type with azo groups inserted in the main chain were prepared. MAIs were then characterized by chemical analyses, spectral methods, H-1-NMR, GPC, and DSC techniques. They were used in the free-radical bulk polymerization of dicyclohexylitaconate to synthesize AB block copolymers of poly( ethylene glycol-b-dicyclohexylitaconate) (PEG-b-PDCHI). (C) 1997 John Wiley & Sons, Inc.
Times Cited: 1
Source item page count: 9
Publication Date: SEP 12
IDS No.: XR148
29-char source abbrev: J APPL POLYM SCI
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012


Record 83 of 108
Author(s): Habbaba MM; Ulgen KO
Title: Analysis of protein adsorption to ion exchangers in a finite bath
Source: JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY 1997, Vol 69, Iss 4, pp 405-414
Publisher: JOHN WILEY & SONS LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,TURKEY
Author Keywords: ion-exchange chromatography; computer simulation; protein purification; models; process design
KeywordsPlus: PERFORMANCE LIQUID-CHROMATOGRAPHY; AMINO-ACIDS; AFFINITY-CHROMATOGRAPHY; PEPTIDES; PREDICTION; DESORPTION
Abstract: The adsorption of proteins to ion exchangers was investigated by finite bath experiments and by computer simulations using existing rate models. Experimental data were obtained for the binding of bovine serum albumin at different feed concentrations to both cation and anion exchangers. The results were interpreted together with model predictions and the values of the parameters characterizing the mass transfer mechanisms as well as the interaction rates of the adsorbate-adsorbent complex were estimated. The best agreement between theory and experiment throughout the whole period of adsorption process was obtained with a complex model where several steps of the overall mechanism were simultaneously controlling the overall rate. The simplified models, which offer rapid solution requiring less computational power, can be used at low feed concentrations of the proteins where the mechanisms controlling the adsorption rate are less complex. As the interaction rate mechanism and the intraparticle mass transfer mechanism in the adsorbent particles are the same in both finite bath and column adsorption systems, the information presented in this paper can be used to predict the protein adsorption in a column chromatography system.
Times Cited: 7
Source item page count: 10
Publication Date: AUG
IDS No.: XQ031
29-char source abbrev: J CHEM TECHNOL BIOTECHNOL
Publisher address: BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD


Record 84 of 108
Author(s): Akin AN; Onsan ZI
Title: The effect of preparation variables on the CO hydrogenation activity of coprecipitated Co/Al2O3 catalysts
Source: JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY 1997, Vol 69, Iss 3, pp 337-344
Publisher: JOHN WILEY & SONS LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
Author Keywords: catalyst preparation; coprecipitation; cobalt-alumina; CO hydrogenation
KeywordsPlus: ALUMINA CATALYSTS; SITE TRANSFER; SURFACE; COBALT; DISPERSION; SUPPORT
Abstract: Studies have been conducted on the effect of preparation variables on the activity of coprecipitated cobalt-alumina catalysts to be used for the production of C-1-C-4 hydrocarbons by CO hydrogenation. The preparation parameters considered were the precipitation pH, the precipitation agent, the metal loading, the reduction temperature and the reduction period. It was found that changing pH precipitation with a constant final pH between 11.0 and 12.5 and the use of NaOH together with nitrates as precursors yielded better catalysts with maximal metal surface area. The optimum cobalt loading for the selective production of C-1-C-4 hydrocarbons is around 35 wt%. Optimum activity and selectivity are obtained by applying an 8-h reduction scheme at 648 K under 100 cm(3) min(-1) hydrogen. Calcination prior to reduction has a detrimental effect on metal surface area and hence on catalytic activity.
Times Cited: 4
Source item page count: 8
Publication Date: JUL
IDS No.: XK010
29-char source abbrev: J CHEM TECHNOL BIOTECHNOL
Publisher address: BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD


Record 85 of 108
Author(s): Celik A; Eraslan S; Gokgoz N; Ilgin H; Basaran S; Bokesoy I; Kayserili H; Apak MY; Kirdar B
Title: Identification of the parental origin of polysomy in two 49,XXXXY cases
Source: CLINICAL GENETICS 1997, Vol 51, Iss 6, pp 426-429
Publisher: MUNKSGAARD INT PUBL LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
BOGAZICI UNIV,DEPT GENET & MOL BIOL,ISTANBUL,TURKEY
ANKARA UNIV,FAC MED,DEPT MED BIOL,TR-06100 ANKARA,TURKEY
UNIV ISTANBUL,INST CHILD HLTH,DIV MED GENET,ISTANBUL,TURKEY
Author Keywords: (CA)(n) repeats; nondisjunction; polysomy X; RFLP analysis; 49;XXXXY
KeywordsPlus: BECKER MUSCULAR-DYSTROPHY; PRENATAL-DIAGNOSIS; X-CHROMOSOME; NONDISJUNCTION; POLYMORPHISMS; REPEAT; DUCHENNE; FAMILIES; CARRIER; REGION
Abstract: The parental origin and mechanism of formation of polysomy X were studied in two polysomic cases, using four X-linked restriction fragment length polymorphisms, three (CA), dinucleotide repeat sequences and one variable number tandem repeat (VNTR) locus as genetic markers. A nonradioactive technique based on the hybridization of the polymerase chain reaction (PCR) product was developed for the analysis of dinucleotide repeats. Segregation analysis using different nonradioactive approaches based on the PCR, revealed that all four X chromosomes were of maternal origin. These data provide additional evidence of an identical mechanism of successive nondisjunctions in maternal meiosis I and II.
Times Cited: 3
Source item page count: 4
Publication Date: JUN
IDS No.: XH250
29-char source abbrev: CLIN GENET
Publisher address: 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK


Record 86 of 108
Author(s): Uzturk D; Akman U
Title: Centralized and decentralized control of retrofit heat-exchanger networks
Source: COMPUTERS & CHEMICAL ENGINEERING 1997, Vol 21, pp S373-S378
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,YSTANBUL,TURKEY
KeywordsPlus: DESIGN
Abstract: A method for optimal retrofit design of heat-exchanger networks that do not posses control variables in their original structures, is presented. Bypasses, as control variables, are placed in order to satisfy hard/soft target-temperature constraint specifications with minimum increase in exchanger areas. Alternative bypass-placement configurations are compared in terms of static flexibility, cost of retrofit design, and resiliency (Morari Resiliency Index). Pairings among the bypasses and controlled target temperatures are selected for the most favorable configuration according to Relative Gain Array criterion. Final control configuration is tested under centralized and decentralized feedback control schemes. Centralized scheme satisfies hard and soft target-temperature constraints and provides smooth response.
Times Cited: 1
Source item page count: 6
Supplement: S
IDS No.: XD313
29-char source abbrev: COMPUT CHEM ENG
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB


Record 87 of 108
Author(s): Orcun S; Discioglu A; Altinel K; Hortacsu O
Title: Scheduling of batch processes: An industrial application in paint industry
Source: COMPUTERS & CHEMICAL ENGINEERING 1997, Vol 21, pp S673-S678
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Addresses: Orcun S, BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
BOGAZICI UNIV,DEPT IND ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
MARSHALL PAINT & VARNISH CO INC,GEBZE,KOCAELI,TURKEY
Author Keywords: batch operations; integer programming; production planning; short term scheduling
Abstract: In this work, the mathematical programming model for optimal scheduling of the operations of a batch processing chemical plant, capable to handle all possible deterministic and many stochastic variations in the set-up and operation times of the batch operations developed previously (Orcun et al., 1996, 1995, and 1994) is applied to operations in a plant of a leading Turkish paint manufacturer. The plant focused on in this work is a multi-product, batch processing plant having a wide variety of products, competing for various process equipment on a production site. The plant under consideration operates with respect to an ''order based'' production policy. Thus, this application can be classified as a short term scheduling of a real case multi-product batch processing plant. The MILP (Mixed Integer Linear Programming) formulation generated as a result of the general modeling framework developed, is solved using the CPLEX 3.0 to obtain schedules maximizing the net operational plant profit under varying market conditions. Moreover, the analysis of the schedules obtained from the solution of the problems formulated yielded some information on the performance, utilization and organization of the production site.
Times Cited: 2
Source item page count: 6
Supplement: S
IDS No.: XD313
29-char source abbrev: COMPUT CHEM ENG
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB


Record 88 of 108
Author(s): Doruker P; Bahar I
Title: Role of water on unfolding kinetics of helical peptides studied by molecular dynamics simulations
Source: BIOPHYSICAL JOURNAL 1997, Vol 72, Iss 6, pp 2445-2456
Publisher: BIOPHYSICAL SOCIETY
Addresses: BOGAZICI UNIV,SCH ENGN,POLYMER RES CTR,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
TUBITAK,ADV POLYMER MAT RES CTR,TR-80815 BEBEK,ISTANBUL,TURKEY
KeywordsPlus: OCCURRING AMINO-ACIDS; COIL STABILITY-CONSTANTS; ALANINE-BASED PEPTIDES; APOLAR SIDE-CHAINS; ALPHA-HELIX; THEORETICAL EVIDENCE; FORMING TENDENCIES; C-PEPTIDE; RIBONUCLEASE; PARAMETERS
Abstract: Molecular dynamics simulations have been carried out with four polypeptides, Ala(13), Val(13), Ser(13), and Ala(4)Gly(5)Ala(,) in vacuo and with explicit hydration, The unfolding of the polypeptides, which are initially fully alpha-helix in conformation, has been monitored during trajectories of 0.3 ns at 350 K, A rank of Ala < Val < Ser < Gly is found in the order of increasing rate of unwinding, The unfolding of Ala(13) and Val(13) is completed in hundreds of picoseconds, while that of Ser(13) is about one order of magnitude faster, The helix content of the peptide containing glycine residues falls to zero within a few picoseconds, Ramachandran plots indicate quite distinct equilibrium distributions and time evolution of dihedral angles in water and in vacuum for each residue type. The unfolding of polyalanine and polyvaline helices is accelerated due to solvation, In contrast, polyserine is more stable in water compared to vacuum, because its side chains can form intramolecular hydrogen bonds with the backbone more readily in vacuum, which disrupts the helix. Distribution functions of the spatial and angular position of water molecules in the proximity of the polypeptide backbone polar groups reveal the stabilization of the coiled structures by hydration. The transition from helix to coil is characterized by the appearance of a new peak in the probability distribution at a specific location characteristic of hydrogen bond formation between water and backbone polar groups. No significant insertion of water molecules is observed at the precise onset of unwinding, while (i, i+3) hydrogen bond formation is frequently detected at the initiation of alpha-helix unwinding.
Times Cited: 9
Source item page count: 12
Publication Date: JUN
IDS No.: XA636
29-char source abbrev: BIOPHYS J
Publisher address: 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998


Record 89 of 108
Author(s): Haliloglu T; Mattice WL
Title: Conformational transitions of end-adsorbed triblock copolymers in a nonselective solvent
Source: MACROMOLECULAR THEORY AND SIMULATIONS 1997, Vol 6, Iss 3, pp 667-677
Publisher: HUTHIG & WEPF VERLAG
Addresses: Haliloglu T, UNIV AKRON,INST POLYMER SCI,AKRON,OH 44325
BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,TR-80815 BEBEK,ISTANBUL,TURKEY
TUBITAK ADV POLYMER MAT RES CTR,TR-80815 BEBEK,TURKEY
KeywordsPlus: ADSORPTION-KINETICS; BLOCK COPOLYMERS; INTERFACE; CHAINS; POLYMERS; SURFACE; FORCES; MICA
Abstract: Conformational dynamics of triblock copolymers end-adsorbed onto a surface from a nonselective solvent have been studied by a Monte Carlo lattice simulation technique. The triblock copolymers are A(NA)B(NB)A(NA) With N-A = 10 and N-B = 5, 10, 20 and 40, at surface interaction parameters epsilon = -0.5 and -1.0. A is the adsorbing block and B is the nonadsorbing block. The number of chains in the periodic box is varied over the range 100 less than or equal to n less than or equal to 500. The triblock copolymer can exist in three states: loop (L), tail (T) and free (F) chain. Fractions of those conformations at different system parameters (n, N-B and epsilon) and the associated lifetimes are calculated from the simulations. A kinetic scheme is constructed and the corresponding transition rate matrix is used in the master formalism equation, the solution of which yields the dynamic modes of the system. A correlation function is defined to produce a single overall view of the rate of transitions between different conformational states. The degree of surface interaction has strong influence on the rate of transitions between the states, in particular, longer average lifetimes and a wider distribution of lifetimes of the loop conformation contribute to the slower decay of the correlation curves. At high surface adsorption, larger N-B decrease the rate of all transitions at all values of a. A weak dependence on n is observed for all sizes of N-B at both surface energies.
Times Cited: 2
Source item page count: 11
Publication Date: MAY
IDS No.: XA610
29-char source abbrev: MACROMOL THEORY SIMUL
Publisher address: AUF DEM WOLF 4, CH-4052 BASEL, SWITZERLAND


Record 90 of 108
Author(s): Hamurcu EE; Hazer B; Baysal BM
Title: Polystyrene-b-polydimethyl siloxane (PDMS) multicomponent polymer networks: Styrene polymerization with macromonomeric initiators (macroinimers) having PDMS units
Source: POLYMER 1997, Vol 38, Iss 12, pp 2981-2987
Publisher: ELSEVIER SCI LTD
Addresses: TUBITAK,MARMARA RES CTR,RES INST BASIC SCI,DEPT CHEM,TR-41470 GEBZE,TURKEY
KARADENIZ TECH UNIV,DEPT CHEM,TR-61080 TRABZON,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,TURKEY
Author Keywords: macroinimer; poly(dimethylsiloxane); poly(S-b-PDMS) polymer network
KeywordsPlus: BLOCK COPOLYMERS; AZO-INITIATORS; MACRO
Abstract: A new macromonomeric initiator (macroinimer) was synthesized and evaluated for the bulk polymerization of styrene at 60 and 80 degrees C. The macroinimer containing poly(dimethylsiloxane), PDMS, was synthesized via condensation reactions between 4,-4'-azobis-4-cyanopentanoyl chloride (ACPC), PDMS and methacryloyl chloride. The product (MIM I) was thermally homopolymerized and copolymerized with styrene in bulk. Kinetics of radical polymerization of styrene with MIM I at 60 degrees C and at low conversion was studied. Rate constant K, k(p)(fk(d)/k(1))(1/2), was estimated from kinetic data as 1.15 x 10(-4) 1(1/2) mol(-1/2) s. Bulk polymerization of styrene with macroinimers at 80 degrees C gave crosslinked block copolymers. D.s.c. measurements showed that crosslinked block copolymers had a glass transition temperature around 45 degrees C. This is evidence of a plasticizing effect of flexible polysiloxane segments in copolymers. Crosslinked PDMS-b-PS block copolymers obtained using macroinimers may be an interesting group of thermoplastic elastomers. (C) 1997 Elsevier Science Ltd.
Times Cited: 0
Source item page count: 7
Publication Date: JUN
IDS No.: XA395
29-char source abbrev: POLYMER
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 91 of 108
Author(s): Kayaman N; Okay O; Baysal BM
Title: Phase transition of polyacrylamide gels in PEG solutions
Source: POLYMER GELS AND NETWORKS 1997, Vol 5, Iss 2, pp 167-184
Publisher: ELSEVIER SCI LTD
Addresses: TUBITAK MARMARA RES CTR,RES INST BASIC SCI,DEPT CHEM,TR-41470 GEBZE,KOCAELI,TURKEY
KOCAELI UNIV,DEPT CHEM,IZMIR,KOCAELI,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
KeywordsPlus: RUBBER-ELASTICITY THEORY; TEMPERATURE-SENSITIVE GELS; POLYMER NETWORKS; POLY(ACRYLIC ACID); POLY(METHACRYLIC ACID); POLY(ETHYLENE GLYCOL); COLLAPSE; EQUILIBRIUM; BEHAVIOR; SWOLLEN
Abstract: Non-ionic polyacrylamide gels immersed in aqueous solutions of poly(ethylene glycol) (PEG) exhibit a continuous volume change upon continuous increase of the PEG concentration in the external solution. The volume change becomes discontinuous when ionizable groups are incorporated into the network. As the proportion of ionizable groups increases, or, as the molecular weight of PEG decreases, the critical concentration of PEG required for a discontinuous volume collapse rises. The distribution of PEG inside and outside the gel phase changes with gel volume; it also exhibits a discontinuous change at the phase transition. Flory-Huggins theory gives a qualitative description of the phenomenon. (C) 1997 Elsevier Science Limited.
Times Cited: 11
Source item page count: 18
IDS No.: XA252
29-char source abbrev: POLYM GELS NETWORKS
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 92 of 108
Author(s): Bahar I; Jernigan RL
Title: Inter-residue potentials in globular proteins and the dominance of highly specific hydrophilic interactions at close separation
Source: JOURNAL OF MOLECULAR BIOLOGY 1997, Vol 266, Iss 1, pp 195-214
Publisher: ACADEMIC PRESS LTD
Addresses: NCI,MOL STRUCT SECT,MATH BIOL LAB,DIV BASIC SCI,NIH,BETHESDA,MD 20892
BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
BOGAZICI UNIV,CTR POLYMER RES,TR-80815 BEBEK,ISTANBUL,TURKEY
TUBITAK,ADV POLYMER MAT RES CTR,TR-80815 BEBEK,ISTANBUL,TURKEY
Author Keywords: potentials of mean force; globular protein structures; radial distribution functions; homogeneous interactions; specific interactions
KeywordsPlus: AMINO-ACID-RESIDUES; SIDE-CHAINS; MEAN FORCE; CONFORMATIONS; HYDROPHOBICITY; PREDICTION; MODELS; SIMULATION; ENSEMBLES; SEQUENCE
Abstract: Residue-specific potentials between pairs of side-chains and pairs of sidechain-backbone interaction sites have been generated by collecting radial distribution data for 302 protein structures. Multiple atomic interactions have been utilized to enhance the specificity and smooth the distance-dependence of the potentials. The potentials are demonstrated to successfully discriminate correct sequences in inverse folding experiments. Many specific effects are observable in the non-bonded potentials; grouping of residue types is inappropriate, since each residue type manifests some unique behavior. Only a weak dependence is seen on protein size and composition. Effective contact potentials operating in three different environments (self, solvent-exposed and residue-exposed) and over any distance range are presented. The effective contact potentials obtained from the integration of radial distributions over the distance interval r less than or equal to 6.4 Angstrom are in excellent agreement with published values. The hydrophobic interactions are verified to be dominantly strong in this range. Comparison of these with a newly derived set of effective contact potentials for closer inter-residue separations (r less than or equal to 4.0 Angstrom) demonstrates drastic changes in the most favorable interactions. In the closer approach case, where the number of pairs with a given residue is approximately one, the highly specific interactions between charged and polar side-chains predominate. These closer approach values could be utilized to select successively the relative positions and directions of residue side-chains in protein simulations, following a hierarchical algorithm optimizing side-chain-side-chain interactions over the two successively closer distance ranges. The homogeneous contribution to stability is stronger than the specific contribution by about a factor of 5. Overall, the total non-bonded interaction energy calculated for individual proteins follows a dependence on the number of residues of the form of n(1.28), indicating an enhanced stability for larger proteins. (C) 1997 Academic Press Limited.
Times Cited: 53
Source item page count: 20
Publication Date: FEB 14
IDS No.: WH768
29-char source abbrev: J MOL BIOL
Publisher address: 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX


Record 93 of 108
Author(s): Haliloglu T; Stevenson DC; Mattice WL
Title: Monte Carlo simulation of the adsorption from a nonselective solvent of symmetric triblock copolymers with sticky end blocks
Source: JOURNAL OF CHEMICAL PHYSICS 1997, Vol 106, Iss 8, pp 3365-3369
Publisher: AMER INST PHYSICS
Addresses: Haliloglu T, BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
BOGAZICI UNIV,CTR POLYMER RES,ISTANBUL,TURKEY
TUBITAK,ADV POLYMER MAT RES CTR,TR-80815 BEBEK,ISTANBUL,TURKEY
UNIV AKRON,DEPT POLYMER SCI,AKRON,OH 44325
KeywordsPlus: DIBLOCK COPOLYMERS; KINETICS; INTERFACE; CHAINS
Abstract: The adsorption of symmetric triblock copolymers from a nonselective solvent on an impenetrable surface has been studied by a lattice Monte Carlo simulation method. The triblock copolymers are A(NA)B(NB)A(NA) with N-A=10, 5 less than or equal to N-B less than or equal to 40, and surface interaction parameters -1.5 less than or equal to epsilon less than or equal to-0.5, where A is the adsorbing block and B is the nonadsorbing block. The concentration, expressed as the volume fraction, is varied over the range 0.012 less than or equal to c less than or equal to 0.143. This report describes the adsorption isotherms and the kinetics of the adsorption in;he simulations. At short times, the adsorption is diffusion controlled. Good approximations to the Langmuir adsorption isotherm are observed for the equilibrium adsorbed amount, Gamma and surface coverage of the adsorbing block, theta(A). The results are compared with recent simulations for diblock copolymers. The adsorbed amount is less for the diblock than for the triblock copolymers at low concentration. The surface coverage by the adsorbing block is the same for both cases at weak surface adsorption. The surface density profiles are also obtained and compared. The adsorbed number of chains per unit area (sigma) and surface coverage for triblock copolymers under: weak adsorption conditions are found, respectively, to scale according to the relationship sigma, theta(A) similar to 1/beta(2), where beta=(N-B/N-A)(3/5), which implies the importance of the nonadsorbing block size for the adsorption features of triblock copolymers. These results confirm the experimental observation reported recently by Dorgan et al. [Macromolecules 26, 5321 (1993)]. (C) 1997 American Institute of Physics.
Times Cited: 4
Source item page count: 5
Publication Date: FEB 22
IDS No.: WH843
29-char source abbrev: J CHEM PHYS
Publisher address: CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999


Record 94 of 108
Author(s): Kopac M; Hortacsu A; Arikol M
Title: Comparative evaluation of some existing rate-type constitutive equations for a viscoelastic fluid undergoing wiggle flow
Source: JOURNAL OF NON-NEWTONIAN FLUID MECHANICS 1997, Vol 68, Iss 1, pp 1-15
Publisher: ELSEVIER SCIENCE BV
Addresses: Kopac M, ZONGULDOK KARAELMAS UNIV,FAC ENGN,DEPT MECH ENGN,TR-67100 ZONGULDOK,TURKEY
BOGAZICI UNIV,FAC ENGN,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
Author Keywords: constitutive equations; non-linear regression; non-newtonian fluid; numerical simulations; viscoelastic fluid; wiggle flow
KeywordsPlus: VELOCITY
Abstract: A comparative evaluation of existing rate-type constitutive equations is provided for a viscoelastic fluid undergoing accelerated flow. To this end, accurate point velocity and stress birefringence data previously obtained by laser Doppler anemometry and stress birefringence are utilized. For each constitutive equation, the numerical values of constants which yield the best fit with experimental data are determined via non-linear regression analysis. The best agreement between experimental and calculated normal stress differences is obtained with the White-Metzner equation. The success of this equation is attributed to the deformation rate dependence of its viscosity and time constant. (C) 1997 Elsevier Science B.V.
Times Cited: 0
Source item page count: 15
Publication Date: JAN
IDS No.: WH652
29-char source abbrev: J NON-NEWTONIAN FLUID MECH
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 95 of 108
Author(s): Ozer EO; Platin S; Akman U; Hortacsu O
Title: Supercritical carbon dioxide extraction of spearmint oil from mint-plant leaves
Source: CANADIAN JOURNAL OF CHEMICAL ENGINEERING 1996, Vol 74, Iss 6, pp 920-928
Publisher: CANADIAN SOC CHEMICAL ENGINEERING
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
Author Keywords: spearmint oil; hydro distillation; supercritical CO2 extraction; selectivity; yield
Abstract: Spearmint oil (essential oil of Mentha spicata) was extracted from Turkish mint-plant leaves using supercritical CO2 in a basket-type extractor. Effects of temperature, pressure, extraction time, amount of CO2, and entrainer (ethanol) concentration on composition of essential-oil extracts and oil yield, relative to hydro-distillation, were investigated. Relative yields were as high as 80%. Monoterpenes fraction in extracts was inversely correlated with relative oil yields. Monoterpenes were preferentially extracted by CO2 due to their high vapor pressure, low molar mass and low polarity. Supercritical extraction presented advantages over the conventional hydro-distillation by yielding extracts lower in monoterpenes fraction and by enabling high yields at temperatures safe for the heat-sensitive essential oil.
Times Cited: 4
Source item page count: 9
Publication Date: DEC
IDS No.: WG866
29-char source abbrev: CAN J CHEM ENG
Publisher address: 130 SLATER ST, STE 550, OTTAWA ON K1P 6E2, CANADA


Record 96 of 108
Author(s): Bahar I; Jernigan RL
Title: Coordination geometry of nonbonded residues in globular proteins
Source: FOLDING & DESIGN 1996, Vol 1, Iss 5, pp 357-370
Publisher: CURRENT BIOLOGY LTD
Addresses: NCI,MOL STRUCT SECT,MATH BIOL LAB,DIV BASIC SCI,NIH,BETHESDA,MD 20892
BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,TR-80815 BEBEK,ISTANBUL,TURKEY
TUBITAK ADV POLYMER MAT RES CTR,TR-80815 BEBEK,ISTANBUL,TURKEY
Author Keywords: coordination geometry; residue packing; specificity of interresidue interactions
KeywordsPlus: SIDE-CHAIN; PACKING; STABILITY; SEQUENCES; FEATURES; FOLD
Abstract: Background: Two opposite Views have been advanced for the packing of sidechains in globular proteins. The first is the jigsaw puzzle model, in which the complementarity of size and shape is essential. The second, the nuts-and-bolts model, suggests that constraints induced by steric complementarity or pairwise specificity have little influence. Here, the angular distributions of sidechains around amino acids of different types are analyzed, in order to capture the preferred (if any) coordination loci in the neighborhood of a given type of amino acid.

Results: Some residue pairs select specific coordination states with probabilities about ten times higher than expected for random distributions. This selectivity becomes more pronounced at closer separations leading to an effective free energy of stabilization as large as -2 RT for some sidechain pairs. A list of the most probable coordination sites around each residue type is presented, along with their statistical weights.

Conclusions: These data provide guidance as to how to pack selectively the nonbonded sidechains in the neighborhood of a central residue for computer generation of unknown protein structures. (C) Current Biology Ltd

Times Cited: 22
Source item page count: 14
IDS No.: WC406
29-char source abbrev: FOLD DES
Publisher address: 34-42 CLEVELAND STREET, LONDON, ENGLAND W1P 6LB


Record 97 of 108
Author(s): Hamurcu EE; Hazer B; Misirli Z; Baysal BM
Title: Preparation and characterization of block and graft copolymers using macroazoinitiators having siloxane units
Source: JOURNAL OF APPLIED POLYMER SCIENCE 1996, Vol 62, Iss 9, pp 1415-1426
Publisher: JOHN WILEY & SONS INC
Addresses: TUBITAK,MARMARA RES CTR,RES INST BASIC SCI,DEPT CHEM,TR-41470 GEBZE,KOCAELI,TURKEY
TUBITAK,MARMARA RES CTR,DEPT MAT SCI,TR-41470 GEBZE,KOCAELI,TURKEY
KARADENIZ TECH UNIV,DEPT CHEM,TR-61080 TRABZON,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
KeywordsPlus: MACRO; INITIATORS
Abstract: alpha,omega-Amine terminated organofunctional polydimethylsiloxane (PDMS) was condensed with 4,4'-azobis-4-cyanopentanoyl chloride (ACPC) to prepare macroazoinitiators containing siloxane units. Interfacial polycondensation reaction at room temperature was applied: ACPC was slightly dissolved in carbon tetrachloride and it was poured on aqueous NaOH solution of PDMS. Block copolymers containing PDMS as a block segment combined with polystyrene (PS) have been derived by the polymerization of styrene monomer initiated by these macroazoinitiators. PS-b-PDMS block copolymers were characterized by using nuclear magnetic resonance and infrared spectroscopy. Thermal and mechanical properties of the block copolymers were studied by using thermogravimetric analysis, differential scanning calorimetry, and a Tensilon stress-strain instrument. The morphology of block copolymers was investigated by scanning electron microscopy. PDMS-g-polybutadiene (PBd) graft copolymers were also prepared by reaction of PBd with the above macroazoinitiator. Increase in the amount of macroazoinitiator in the mixture of PBd (52% w/w) leads to the formation of crosslinked graft copolymers. Molecular weights of soluble graft copolymer samples were between 450 and 600 K with a polydispersity of 2.0-2.3. (C) 1996 John Wiley & Sons, Inc.
Times Cited: 4
Source item page count: 12
Publication Date: NOV 28
IDS No.: VN880
29-char source abbrev: J APPL POLYM SCI
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012


Record 98 of 108
Author(s): Aksoylu AE; Akin AN; Onsan ZI; Trimm DL
Title: Structure/activity relationships in coprecipitated nickel-alumina catalysts using CO2 adsorption and methanation
Source: APPLIED CATALYSIS A-GENERAL 1996, Vol 145, Iss 1-2, pp 185-193
Publisher: ELSEVIER SCIENCE BV
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,TR-80815 BEBEK,ISTANBUL,TURKEY
UNIV NEW S WALES,SCH CHEM ENGN & IND CHEM,KENSINGTON,NSW 2033,AUSTRALIA
Author Keywords: nickel/alumina; coprecipitated nickel/alumina; carbon dioxide adsorption; carbon dioxide methanation
KeywordsPlus: GROUP-VIII METALS; HYDROGENATION; MORPHOLOGY
Abstract: A series of coprecipitated Ni/Al2O3 catalysts containing 0-25 wt.-% Ni were examined for total surface area, total pore volume, metal surface area, CO2 adsorption and CO2 methanation activity in order to study the relation between metal content, structure and catalyst activity. Coprecipitated Ni/Al2O3 catalysts are found to be efficient promoters for methanation. Methanation activity is dependent on the nickel content and the degree of CO2 adsorption at the reaction considered. Although Al2O3 does not exhibit methanation activity, it is found to be active for CO2 adsorption. Reverse spillover increases methane production per unit nickel surface particularly for catalysts with low Ni loadings.
Times Cited: 6
Source item page count: 9
Publication Date: OCT 8
IDS No.: VL822
29-char source abbrev: APPL CATAL A-GEN
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 99 of 108
Author(s): Yilmaz F; Baysal BM
Title: Application of thermal blob theory to intrinsic viscosity measurements of poly(4-chlorostyrene) above the theta point
Source: JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS 1996, Vol 34, Iss 10, pp 1789-1793
Publisher: JOHN WILEY & SONS INC
Addresses: TUBITAK,MARMARA RES CTR,RES INST BASIC SCI,DEPT CHEM,GEBZE 41470,TURKEY
TECH UNIV YILDIZ,DEPT CHEM,SISLI 80270,ISTANBUL,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,ISTANBUL,TURKEY
Author Keywords: blob theory; viscosity; poly(4-chlorostyrene); theta point
KeywordsPlus: LINEAR POLYMER DIMENSIONS; TEMPERATURE-DEPENDENCE; COLLAPSED REGIME; HYDRODYNAMIC RADIUS; MOLECULAR-WEIGHT; FLEXIBLE COILS; TRANSITION; POLYSTYRENE; CYCLOHEXANE; SYSTEM
Abstract: Macromolecular chains obey purely Gaussian statistics close to the theta temperature. An asymptotic regime is also reached far above the theta point. Thermal blob theory permits an approximate calculation of thermal expansion factor. In this theory, an adjustable pa rameter is used as a prefactor (A*N-1) in order to calculate the reduced blob parameter (Nl N-c). In this work, we proposed a different approach to evaluate (A*N-1) by plotting tau M(omega)(1/2)/alpha(eta)(5) against tau M(omega)(1/2). Chain expansion data of poly(4-chlorostyrene) in various solvents is used to evaluate viscosity expansion factors at various temperatures. It seems that predictions of thermal blob theory provide a better fit to experimental points rather than those evaluations based on Flory-type approaches. (C) 1996 John Wiley & Sons, Inc.
Times Cited: 0
Source item page count: 5
Publication Date: JUL 30
IDS No.: UU547
29-char source abbrev: J POLYM SCI B-POLYM PHYS
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012


Record 100 of 108
Author(s): Gonenc ZS; Akman U; Sunol AK
Title: Analysis of retention in supercritical fluid chromatography and its relation to solubility
Source: TURKISH JOURNAL OF CHEMISTRY 1996, Vol 20, Iss 1, pp 9-26
Publisher: SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY
Addresses: UNIV S FLORIDA,DEPT CHEM ENGN,TAMPA,FL 33620
BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,ISTANBUL,TURKEY
KeywordsPlus: PARTIAL MOLAR VOLUME; CARBON-DIOXIDE; STATIONARY PHASE; MOBILE PHASE; SOLUTE; LIQUID
Abstract: The effects of temperature, pressure and supercritical fluid density on the solubility-retention relationship of solutes in supercritical fluid chromatography are investigated. New retention data for naphthalene, phenanthrene, benzoic acid and 2-methoxy-naphthalene is obtained as a function of pressure at different temperatures. The bulk of the data is taken near the critical region of the mobile gas where the anomalities are expected. This data is used to compare two approaches for thermodynamic modeling of pressure dependence of solute retention. In these approaches, mobile-phase partial molar volumes of the solutes are determined either from bulk solubility data or from infinite-dilution fugacity coefficients. In both approaches, an integrated from of retention pressure relation is utilized to explicitly reveal the nature of interactions between the stationary phase and the solute. The approach that utilizes infinite-dilution fugacity coefficient better predicts the pressure dependence of retention, especially for solutes that are substantially soluble near the critical point of the mobile phase. Relationships between pressure and temperature dependence of solubility and retention of solutes are also investigated.
Times Cited: 0
Source item page count: 18
IDS No.: UT103
29-char source abbrev: TURK J CHEM
Publisher address: PO BOX 605 YENISEHIR, 06445 ANKARA, TURKEY


Record 101 of 108
Author(s): Aksoylu AE; Akin AN; Sunol SG; Onsan ZI
Title: The effect of metal loading on the adsorption parameters of carbon dioxide on coprecipitated nickel-alumina catalysts
Source: TURKISH JOURNAL OF CHEMISTRY 1996, Vol 20, Iss 1, pp 88-94
Publisher: SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY
Addresses: Aksoylu AE, BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,ISTANBUL,TURKEY
Author Keywords: nickel-alumina; coprecipitated nickel-alumina; CO2 adsorption
KeywordsPlus: GROUP-VIII METALS; HYDROGENATION; HYDROCARBONS; METHANATION; GAS; CO2
Abstract: A coprecipitation method has been developed and modified for the preparation of nickel-alumina catalysts having metal loadings in the 0-25 wt% Ni range. The effect of metal loading on CO2 adsorption was investigated under isothermal chromatographic conditions using an elution technique in the temperature range 483-533 K. Average enthalpies of adsorption were determined using the isosteres obtained from the experimental adsorption isotherms. The isotherms were also fitted to the Langmuir equation for the evaluation of adsorption equilibrium coefficients, Gibbs free energies, average adsorption enthalpies and entropies.
Times Cited: 3
Source item page count: 7
IDS No.: UT103
29-char source abbrev: TURK J CHEM
Publisher address: PO BOX 605 YENISEHIR, 06445 ANKARA, TURKEY


Record 102 of 108
Author(s): Boyaci C; Uzturk D; Konukman AES; Akman U
Title: Dynamics and optimal control of flexible heat-exchanger networks
Source: COMPUTERS & CHEMICAL ENGINEERING 1996, Vol 20, pp S775-S780
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Addresses: Boyaci C, BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,ISTANBUL,TURKEY
Abstract: A distributed-parameter model of multi-tube, single-pass heat exchangers are used to construct the dynamic model of a heat-exchanger network (HEN). Based on the control-vector parameterization technique, open-loop (time-dependent bypass manipulation) and closed-loop (target-temperature dependent bypass manipulation) centralized optimal-control schemes are developed and tested. The parameterizations are done in such a way that the manipulated variables approach and eventually match the values obtained from static optimization which refers to an algebraic model of the HEN. Manipulation of the bypasses linearly in time up to their optimal values results in a quite satisfactory dynamic response of the HEN and eliminates temporary violations of the target-temperature control-precision constraints.
Times Cited: 2
Source item page count: 6
Supplement: B
IDS No.: UR310
29-char source abbrev: COMPUT CHEM ENG
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB


Record 103 of 108
Author(s): Uzturk D; Konukman AES; Boyaci C; Akman U
Title: Operability of an autothermal reactor linked to a flexible heat-exchanger network
Source: COMPUTERS & CHEMICAL ENGINEERING 1996, Vol 20, pp S943-S948
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Addresses: Uzturk D, BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,ISTANBUL,TURKEY
KeywordsPlus: PROCESS DESIGN; INDEX
Abstract: Operability of an autothermal fixed-bed catalytic reactor within a Heat-Exchanger Network (HEN) is investigated. A retrofit HEN is designed by considering the critical temperature deviations that cause run-away behavior for the reactor. The flexible retrofit design is of minimum cost (area) and keeps both the hot-spot temperature (maximum temperature rise) in the reactor within a strict safety margin and the overall conversion within a strict feasibility margin against a set of possible disturbance directions. The flexible retrofit HEN enables creation of favorable disturbance-propagation paths via optimal manipulation of bypass-stream flow rates, and thus, increases the operability and controllability of the autothermal reactor within the HEN.
Times Cited: 2
Source item page count: 6
Supplement: B
IDS No.: UR310
29-char source abbrev: COMPUT CHEM ENG
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB


Record 104 of 108
Author(s): Orcun S; Altinel IK; Hortacsu O
Title: Scheduling of batch processes with operational uncertainties
Source: COMPUTERS & CHEMICAL ENGINEERING 1996, Vol 20, pp S1191-S1196
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Addresses: Orcun S, BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,ISTANBUL,TURKEY
BOGAZICI UNIV,DEPT IND ENGN,BEBEK 80815,ISTANBUL,TURKEY
Author Keywords: scheduling; batch operations; integer programming; production planning; stochastic optimization
KeywordsPlus: CHEMICAL-PLANTS; MULTIPURPOSE
Abstract: In this work, a mathematical programming model for optimal scheduling of the operations of a batch processing chemical plant is developed. The model is capable to handle all possible deterministic variations in the set-up and operation times of batch operations, and the model is sufficiently general to include the uncertainties introduced by the probabilistic behavior of set-up and operation times of batches when such variations can be mathematically defined. It is shown that the probabilistic model can be reduced to a Mixed Integer Non-Linear Program (MINLP), once the probability distribution functions used to model the random variations are defined. The resulting MINLP is then linearized and solved for small examples using CPLEX 3.0 in order to obtain a schedule which maximizes the net expected operational profit.
Times Cited: 3
Source item page count: 6
Supplement: B
IDS No.: UR310
29-char source abbrev: COMPUT CHEM ENG
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB


Record 105 of 108
Author(s): Eroglu MS; Hazer B; Guven O; Baysal BM
Title: Preparation and thermal characterization of block copolymers by macroazonitriles having glycidyl azide and epichlorohydrin moieties
Source: JOURNAL OF APPLIED POLYMER SCIENCE 1996, Vol 60, Iss 12, pp 2141-2147
Publisher: JOHN WILEY & SONS INC
Addresses: TUBITAK,MARMARA RES CTR,RES INST BASIC SCI,DEPT CHEM,GEBZE 41470,TURKEY
KARADENIZ TECH UNIV,DEPT CHEM,TRABZON 61080,TURKEY
HACETTEPE UNIV,DEPT CHEM,BEYTEPE 06532,ANKARA,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,ISTANBUL,TURKEY
Abstract: Poly(glycidyl azide) (PGA) an energetic polymer and polyepichlorohydrin (PECH) were condensed with 4,4' azobis(4-cyanopentanoyl chloride) (ACPC) to prepare macro-azo-initiators. Block copolymers containing each of these polyethers as a block segment combined with polystyrene (PS) or poly(vinyl acetate) (PVAc) have been drived by the polymerization of monomers initiated with this macro-azo-initiators. Thermal properties of block copolymers were investigated with differential scanning calorimetry (DSC) and thermogravimetry. DSC traces showed single glass transition temperatures in between the related segments of copolymers. Dynamic thermogravimetric analysis revealed the individual degradation behaviors of block segments (C) 1996 John Wiley & Sons, Inc.
Times Cited: 5
Source item page count: 7
Publication Date: JUN 20
IDS No.: UM890
29-char source abbrev: J APPL POLYM SCI
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012


Record 106 of 108
Author(s): Baysal BM; Uyanik N; Hamurcu EE; Cvetkovska M
Title: Styrene polymerization with a macroinitiator having siloxane units
Source: JOURNAL OF APPLIED POLYMER SCIENCE 1996, Vol 60, Iss 9, pp 1369-1378
Publisher: JOHN WILEY & SONS INC
Addresses: Baysal BM, TUBITAK,MARMARA RES CTR,RES INST BASIC SCI,DEPT CHEM,POB 21,GEBZE 41470,KOCAELI,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL 80815,TURKEY
ISTANBUL TECH UNIV,DEPT CHEM,ISTANBUL 80626,TURKEY
UNIV ST CYRIL & METHUDIUS,FAC TECHNOL & MET,SKOPJE,MACEDONIA
KeywordsPlus: COPOLYMERS
Abstract: Block copolymers containing segments of poly(dimethylsiloxane) (PDMS) and polystyrene were synthesized. Dihydroxy terminated PDMS M(n) 2500 g/mol, was reacted with an aliphatic diisocyanate (isophorone diisocyanate) and an aliphatic hydroperoxide (t-butyl hydroperoxide). The resulting polymeric peroxycarbamate having siloxane units (a new macroinitiator) was used as free radical initiator for vinyl polymerization of styrene. Formation of block copolymers was illustrated by several characterization methods such as chemical and spectroscopic analysis, fractionation, and GPC. Mechanical and thermal characterization of the copolymers were made by stress-strain tests and DSC. The surface properties and the morphology of the block copolymers were investigated by contact angle measurements and SEM. (C) 1996 John Wiley & Sons, Inc.
Times Cited: 7
Source item page count: 10
Publication Date: MAY 31
IDS No.: UK881
29-char source abbrev: J APPL POLYM SCI
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012


Record 107 of 108
Author(s): Akman U; Sunol GSG; Sunol AK
Title: A comparison of supercritical partition and supercritical adsorption chromatographies
Source: TURKISH JOURNAL OF CHEMISTRY 1995, Vol 19, Iss 4, pp 263-274
Publisher: SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,ISTANBUL,TURKEY
UNIV S FLORIDA,DEPT CHEM ENGN,TAMPA,FL 33620
KeywordsPlus: PARTIAL MOLAR VOLUME; FLUID CHROMATOGRAPHY; CARBON-DIOXIDE; STATIONARY PHASE; MOBILE PHASE; RETENTION; SOLUTE; SOLUBILITY; PRESSURE; DEPENDENCE
Abstract: Implications of the partial molar volume of solute in the stationary-phase material in both superciritical partition chromatography and supercritical adsorption chromatography are discussed within the framework of a thermodynamic model of solute retention. Using experimental retention data and the thermodynamic model it is illustrated that, in supercritical partititon chromatography, relationships among solubility, sorption and retention are confounded by the effects (pressure dependence) of the partial molar volume of solute in the stationary-phase material and possible swelling of the stationary-phase material by the supercritical mobile-phase fluid. For the first time in the literature, a supercritical sorption isotherm is imbedded in the thermodynamic model of solute retention in order to simulate temperature, pressure and density dependence of solute retention in supercirical adsorption chromatography. Unlike the behavior predicted by the model of solute retention in supercritical partition chromatography, simulation of pressure dependence of solute retention in supercritical adsorption chromatograpy with the aid of supercritical sorption isotherm does not show a retention minimum, and the retention coefficient exhibits an asymptotic decrease to aero with increasing pressure as expected. It is demonstrated that in supercritical adsorption chromatograpy the direct inverse relationship present between the solute's solubility and sorption also exists between solubility (solvent power) and retention but as weighted by the molar volume of the mobile phase.
Times Cited: 0
Source item page count: 12
IDS No.: TW248
29-char source abbrev: TURK J CHEM
Publisher address: PO BOX 605 YENISEHIR, 06445 ANKARA, TURKEY


Record 108 of 108
Author(s): Hortacsu O; Aeskinazi O; Akman U
Title: Release mechanisms of extractable compounds from plant matrices during supercritical fluid extraction - Mathematical modeling
Source: INNOVATIONS IN SUPERCRITICAL FLUIDS 1995, Vol 608, pp 364-378
Publisher: AMER CHEMICAL SOC
Addresses: Hortacsu O, BOGAZICI UNIV,DEPT CHEM ENGN,BEBECK 80815,ISTANBUL,TURKEY
Abstract: Two mathematical models: Cellular Permeable-Tube Arrays (CPTA) model and Serially-Interconnected Perfectly-Mixed Tanks (SI-PMTs) model were proposed in an attempt to explain the release mechanisms of extractable compounds from plant matrices during supercritical fluid extraction. Models enable phenomenological description of probable three-phase mass transfer taking place within plant cells. A complex chromatographic-type release is envisioned for the supercritical-fluid extraction of materials from plant matrices. A parametric sensitivity analysis is conducted on the SI-PMTs
Times Cited: 3
Source item page count: 15
Book series title: ACS SYMPOSIUM SERIES
IDS No.: BE38K
29-char source abbrev: ACS SYMP SER
Publisher address: 1155 SIXTEENTH ST NW, WASHINGTON, DC 20036