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  • 1
    Electronic Resource
    Electronic Resource
    Model assembly study of the ligand binding by p-hydroxybenzoate hydroxylase: Correlation between the calculated binding energies and the experimental dissociation constants (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 21 (1995), S. 22-29 
    Details
    ISSN: 0887-3585
    Keywords: solvation ; electrostatic interaction ; proton transfer ; ab initio quantum mechanical ; semiempirical quantum mechanical ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The energies of binding of seven ligands by p-hydroxybenzoate hydroxylase (PHBH) were calculated theoretically. Direct enzyme-ligand interaction energies were calculated using the ab initio quantum mechanical model assembly of the active site at the 3-21G level. Solvation energies of the ligands needed in the evaluation of the binding energies were calculated with the semiempirical AM1-SM2 method and the long-range electrostatic interaction energies between the ligands and the protein matrix classically using the static charge distributions of the ligands and the protein. Energies for proton-transfer between the ligands OH or SH substituent at position 4 and the active-site tyrosine within the ab initio model assemblies were calculated and compared to the corresponding pKas in aqueous solution. Excluding 3,4-dihydroxybenzoate, the natural product of PHBH, a linear relationship between the calculated binding energies and the experimental binding free energies was found with a correlation coefficient of 0.90. Contributions of the direct enzyme-ligand interaction energies, solvation energies and the long-range electrostatic interaction energies to the calculated binding energies were analyzed. The proton-transfer energies of the ligands with substituents ortho to the ionized OH were found to be perturbed less in the model calculations than the energies of their meta isomers as deduced from the corresponding pKas. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340210104
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  • 2
    Electronic Resource
    Electronic Resource
    Modification of olefin polymerization catalysts. I. Mechanism of the interaction between AIEt3 and silyl ethers (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 3241-3253 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction between AlEt3 and silyl ethers, PhnSi(OMe)4-n (n = 0-3), was followed by 13C- and 29Si-NMR techniques in conditions close to those typical for an olefin polymerization reaction with supported Ziegler-Natta catalysts (A1Et3:silyl ether ratios from 1 to 10, temperature range 25-75°C). A1Et3 and silyl ethers form instantaneously at ambient temperature a donor-acceptor complex, which is stable at a 1:1 molar ratio. In the presence of excess A1Et3 the complex decomposes via a mechanism consisting, in the case of PhSi(OMe)3, of five consecutive steps: alternating complexation and ether reductions with the formation of alkylated silyl ethers, Ph(Et)nSi(OMe)3-n (n = 1,2), and dialkyl-aluminum alkoxides, (Et2A1OMe3)n (n = 2,3). The rate of decomposition was enhanced by the increasing number of methoxy groups present in the silyl ether, heating, or a high A1Et3:silyl ether ratio. The decomposition was not inhibited by the presence of 1-hexene.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080251206
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  • 3
    Electronic Resource
    Electronic Resource
    Quantum mechanical model assembly study on the energetics of binding of arabinose, fucose, and galactose to L-arabinose-binding protein (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 20 (1994), S. 367-372 
    Details
    ISSN: 0887-3585
    Keywords: ligand binding ; ab initio quantum mechanics ; semiempirical quantum mechanics ; solvation ; sugars ; binding energies ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Binding energies ofL-arabinose, D-fucose, and D-galactose to L-arabinose-binding protein was investigated theoretically. The calculated binding energies were composed of three contributions: (1) direct ligand-active site interaction energies calculated using static ab initio model assemblies; (2) solvation energies of the ligands; and (3) long-range electrostatic interaction energies between the ligands and the protein matrix. The calculated binding energies and the contributions of the energy components were used to analyze the experimental affinities of the ligands. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340200409
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  • 4
    Electronic Resource
    Electronic Resource
    Ab initio models for receptor-ligand interactions in proteins. 4. Model assembly study of the catalytic mechanism of triosephosphate isomerase (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 225-236 
    Details
    ISSN: 0887-3585
    Keywords: enzyme reaction ; ab initio quantum mechanical ; semiempirical quantum mechanical ; continuum electrostatics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The catalytic mechanism of triosephosphate isomerase (TIM) was investigated with ab initio quantum mechanical calculations. Electrostatic interactions between the quantum mechanical active site and the protein and solvent environment were modeled using the finite difference Poission-Boltzman method. The complexes of TIM with the substrate dihydroxyacetone phosphate (DHAP), five possible intermediates and the product glyceraldehyde-3-phosphate (GAP) were optimized in the active-site model at the 3-21G(*) level and energy profile for the proton abstraction from DHAP by the active-site Glu167 was calculated at the MP2/3-21G(*)//3-21G(*) level. Calculated energetics of the enzyme reaction were found to be in reasonable agreement with the experimental findings. Calculations revealed that an enediol of the substrate is a probable intermediate in the enzyme reaction. It was suggested that the proton abstracted from the substrate by the active-site glutamate goes to the carbonyl oxygen of the substrate producing enediol intermediate either directly or after it is exchanged with solvent. © 1996 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.8
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  • 5
    Electronic Resource
    Electronic Resource
    Selective Formation of cis(X)- and trans(X)-Ru(dmbpy)(CO)2X2 Complexes (X = Cl, Br, I, SCN) from Monomeric and Dimeric Ru-mono(dmbpy) Carbonyl Complexes (Dmbpy = 4,4′-Dimethyl-2,2′-bipyridine) (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 101-106 
    Details
    ISSN: 1434-1948
    Keywords: Ruthenium ; Halogens ; Carbonyl complexes ; Structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aqueous hydrogen halides HX (X = Cl, Br, I) are shown to be excellent halogen sources for the synthesis of a series of halogen-containing ruthenium mono(2,2′-bipyridine) carbonyl complexes Ru(dmbpy)(CO)2X2 (dmbpy = 4,4′-dimethyl-2,2′-bipyridine), as well as effective reagents for the attack of the Ru-Ru bond in the dimer [Ru(dmbpy)(CO)2Cl]2. Selective syntheses were established for both cis- and trans-halogen complexes in the case of Cl- and of Br-containing derivatives, but the only stable isomer containing iodine was trans(I)-Ru(dmbpy)(CO)2I2. The failure to obtain the cis isomer was probably due to sterical effects. Furthermore, a novel S-bound trans(SCN) analogue was synthesized and structurally characterized. In all experiments, the reaction conditions selected led to complete halogen exchange; no mixed halogen or pseudohalogen complexes were detected.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 6
    Electronic Resource
    Electronic Resource
    Syntheses and Characterization of New Tertiary Phosphane Ligands Prepared from p-Anisyl- and p-Thioanisyldichlorophosphanes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1253-1258 
    Details
    ISSN: 1434-1948
    Keywords: Phosphane ligands ; 31P-NMR spectrometry ; Substituent increments ; Electronic and steric properties ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses and spectroscopic parameters of the new tertiary phosphane ligands (p-MeOC6H4)(o-MeOC6H4)2P (1), (p-MeOC6H4)(o-MeSC6H4)2P (2), (p-MeSC6H4)(o-MeSC6H4)2P (3), (p-MeSC6H4)(o-MeOC6H4)2P (4), (p-MeOC6H4)(o-NC5H4)2P (5), and (p-MeSC6H4)(o-NC5H4)2P (6) are reported. Single-crystal X-ray structures of all the compounds (1-6) have been determined. The dependence of the 31P-NMR chemical shifts on the substituent groups of the phosphanes is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 7
    Electronic Resource
    Electronic Resource
    A novel MgCl2-supported Ziegler-Natta catalyst composition: Stereospecific polymerization of propene without external donor (1993)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 14 (1993), S. 133-137 
    Details
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1993.030140212
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