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  • 1
    Electronic Resource
    Electronic Resource
    The temperature dependence of steady-state kinetics: What can be learned about pig liver esterase stereospecificity? (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 11-16 
    Details
    ISSN: 0899-0042
    Keywords: substrate enantioselectivity ; product enantioselectivity ; chirality ; activation enthalpy ; activation entropy ; chiral HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The steady-state kinetic parameters for pig liver carboxylesterase (PLE)-catalyzed hydrolysis of the prochiral substrate dimethyl phenylmalonate (DMPM) (product enantioselectivity) and the separate enantiomers of three chiral 2-phenylpropionic acid esters (substrate enantioselectivity) were measured at seven temperatures between 288 K and 312 K. Arrhenius plots of turnover numbers against the reciprocal of experimental temperatures yielded enthalpies and entropies of activation at enzyme saturation. (+)-(S)-methyl-2-phenylpropionate, (+)-(S)-4-nitrophenyl 2-phenylpropionate, and both enantiomers of phenyl 2-phenylpropionate showed very similar activation enthalpies and entropies (approximately 50 kJ mol-1 and -50 J mol-1 K-1, respectively), but differences were observed for (-)-(R)-methyl 2-phenylpropionate and (-)-(R)-4-nitrophenyl 2-phenylpropionate. Whereas the entropies of activation of all 2-phenylpropionates were negative, positive entropies of activation were measured in the formation of monomethyl phenylmalonate enantiomers from DMPM. Enthalpy-entropy compensation analysis of the data indicates a common mechanism of PLE substrate and product enantiospecificity in the reactions studied here. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530060105
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  • 2
    Electronic Resource
    Electronic Resource
    Metabolic chiral inversion of ibuprofen in isolated rat hepatocytes (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 2 (1990), S. 74-78 
    Details
    ISSN: 0899-0042
    Keywords: ibuprofen ; in vitro metabolism ; chiral inversion ; rat hepatocytes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ibuprofen was used to demonstrate that isolated rat hepatocytes offer a suitable in vitro model to investigate the metabolic chiral inversion of anti-inflammatory 2-arylpropionic acids (profens). The inversion of the pharmacologically inactive (-)-(R)-ibuprofen to the active (+)-(S)-ibuprofen was shown to obey apparent first-order kinetics during 5 h and to increase linearly with increasing hepatocyte concentration up to 4 × 105 cells/ml. No elimination of (R)-ibuprofen by routes other than inversion was seen, whereas the elimination of (S)-ibuprofen appeared to be saturable.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530020203
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  • 3
    Electronic Resource
    Electronic Resource
    Structural Factors Affecting the Basicity of ω-Pyridylalkanols, ω-Pyridylalkanamides and ω-Pyridylalkylamines (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 1868-1884 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The present paper describes the preparation by conventional methods (when not available commercially) and the pKa-determination of the α-, β- and γ-isomers of pyridylethanamide, 3-pyridylpropanamide. 4-pyridylbutanamide, 5-pyridyl-pentanamide, pyridylmethanol, 2-pyridylethanol, 3-pyridylpropanol, 4-pyridyl-butanol, 5-pyridylpentanol, pyridylmethylamine, 2-pyridylethylamine, 3-pyridyl-propylamine, 4-pyridylbutylamine, and 5-pyridylpentylamine. While a field effect accounts for many variations in pKa as a function of chain length, marked inductive effects are operative in some methyl and ethyl homologs. The pKa-decreasing influence of an intramolecular H-bond is also apparent in some lower homologs belonging to the α-series.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650621
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  • 4
    Electronic Resource
    Electronic Resource
    Modelling the Metabolic Epimerization of Anti-inflammatory 2-Arylpropanoyl-coenzyme-A Conjugates: Solvent effects on the 1H/2H exchange in S-[2-(dimethylamino)ethyl] 2-phenylpropanethioate (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1225-1232 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H/2H exchange at the methine position of S-[2-(dimethylamino)ethyl] 2-phenylpropanethioate (DEPP) in solvent/D2O mixtures was taken as a model reaction for the metabolic epimerization of 2-arylpropanoyl-coenzyme-A thioesters and was monitored by 1H-NMR spectroscopy at 37°. The solvents used were (D6)acetone, (D3)acetonitrile, (D6)dimethylsulfoxide, and (D5)pyridine. In the investigated range of D2O percentage (10-50%), the exchange reaction was found to increase linearily with D2O content and with the basicity of the organic solvent, the fastest rates being close to 0.09 h-1 (t½ ca. 8 h). These rates are slower than those observed in vivo for the configurational inversion of profens, and they are elicited in totally unphysiological concentrations of bases. The hypothesis thus formulated is that the metabolic epimerization of 2-arylpropanoyl-coenzyme-A thioesters cannot occur nonenzymatically.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720606
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