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A Computational Comparison of Oxygen Atom Transfer Catalyzed by Dimethyl Sulfoxide Reductase with Mo and W
Author(s) -
Li Jilai,
Andrejić Milica,
Mata Ricardo A.,
Ryde Ulf
Publication year - 2015
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201500209
Subject(s) - chemistry , density functional theory , catalysis , solvation , exothermic reaction , molybdenum , computational chemistry , molecule , activation energy , inorganic chemistry , organic chemistry
A thorough computational study has been performed to investigate oxygen atom transfer (OAT) reactions catalyzed by dimethyl sulfoxide reductase (DMSOR) with a catalytic molybdenum or tungsten ion. Thirteen different density functional theory (DFT) methods have been employed to obtain structural parameters along the reaction pathway, and single‐point energies were computed with local correlation coupled‐cluster methods [LCCSD(T0)]. For both Mo and W, most DFT methods indicate that the enzyme follows a two‐step mechanism with a stable intermediate in which a DMSO molecule coordinates to the metal ion in the +IV oxidation state, and this is also confirmed by the LCCSD(T0) energies. The W‐substituted models have a 26–30 kJ/mol lower activation barrier for the OAT reaction, and the reaction is 63–70 kJ/mol more exothermic than that with Mo. Different DFT methods give widely different activation and reaction energies, which roughly depend on the amount of exact exchange in the method; these differences are also reflected in the structures, especially for the rate‐limiting transition state. Consequently, there is quite a large variation in energies and various energy corrections (thermal, solvation, dispersion, and relativistic; up to 39 kJ/mol) depending on which DFT method is used to obtain the geometries. Therefore, a mechanism predicted by a single method should be viewed with caution.