Influence of Equatorial CH???O Interactions on Secondary Kinetic Isotope Effects for Methyl Transfer.
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ABSTRACT: DFT calculations for methyl cation complexed within a constrained cage of water molecules permit the controlled manipulation of the "axial" donor/acceptor distance and the "equatorial" distance to hydrogen-bond acceptors. The kinetic isotope effect k(CH3)/k(CT3) for methyl transfer within a cage with a short axial distance becomes less inverse for shorter equatorial C???O distances: a decrease of 0.5?Å results in a 3?% increase at 298?K. Kinetic isotope effects in AdoMet-dependent methyltransferases may be m?odulated by CH???O hydrogen bonding, and factors other than axial compression may contribute, at least partially, to recently reported isotope-effect variations for catechol-O-methyltransferase and its mutant structures.
SUBMITTER: Wilson PB
PROVIDER: S-EPMC4770435 | biostudies-literature | 2016 Feb
REPOSITORIES: biostudies-literature
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