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  • 2000-2004  (2)
  • 1975-1979
  • Enzymatic mechanism  (1)
  • Key words: Proton transfer – Serine – Continuum solvent model – Nonequilibrium effects  (1)
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  • 2000-2004  (2)
  • 1975-1979
Year
Keywords
  • 1
    ISSN: 0948-5023
    Keywords: Hybrid methods ; QM/MM ; LSCF ; Zinc metalloproteases ; Thermolysin ; Peptide hydrolysis ; Enzymatic mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrolysis by thermolysin of a Gly-Phe-Leu peptide, considered as a model substrate of the enkephalin family, has been studied with a mixed QM/MM method with the AM1/AMBER parameterization. This study is based on the mechanism proposed by Matthews in which the Glu-143 residue plays the role of a proton shuttle in the course of the reaction. The study focused on the description of every step of the process, reaction intermediates and transition states, and on the influence, both energetical and structural, of the whole protein on these stationary points. The overall mechanism appears to be quite realistic, but the study shows that some reaction steps that were assumed to be concerted should occur in two phases. Analysis of the role of the amino-acids surrounding the active site has shown their important participation in the fluctuations of the energy. In particular, the major role of His-231 on the overall mechanism has been confirmed. This study shows that modeling reaction mechanisms for enzymes is quite feasible and opens the way for computer experiments that may be helpful in devising and interpreting detailed experimental investigations.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2234
    Keywords: Key words: Proton transfer – Serine – Continuum solvent model – Nonequilibrium effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. Serine amino acid in aqueous solution is theoretically studied at the B3PW91/6-31+G** level using a dielectric continuum solvent model. Neutral and zwitterionic structures in the gas phase and in solution are described and the proton-transfer mechanism is discussed. A neutral conformation in which the carboxyl hydrogen atom is already oriented toward the amino group seems to be the absolute energy minimum in the gas phase and the most stable neutral form in solution. The absolute energy minimum in solution is a zwitterionic form. The energy barrier for proton transfer is predicted to be very small, in particular when zero-point-energy contributions are added. Our calculations allow the dynamic aspects of the ionization mechanism to be discussed by incorporating nonequilibrium effects.
    Type of Medium: Electronic Resource
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