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Quantum chemical modeling of CO oxidation by the active site of molybdenum CO dehydrogenase
Author(s) -
Siegbahn Per E. M.,
Shestakov Alexander F.
Publication year - 2005
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.20230
Subject(s) - molybdenum , chemistry , catalysis , molecule , bond cleavage , catalytic cycle , quantum chemical , active site , proton , computational chemistry , photochemistry , chemical physics , inorganic chemistry , organic chemistry , physics , quantum mechanics
The catalytic mechanism of molybdenum containing CO dehydrogenase has been studied using hybrid DFT methods with quite large chemical models. The recent high‐resolution X‐ray structure, showing the surprising presence of copper linked to molybdenum, was used as a starting point. A pathway was initially found with a low barrier for CO bond formation and CO 2 release. However, this pathway did not include the formation of any SCO 2 species, which had been suggested by experiments with an n ‐butylisocyanide inhibitor. When these SCO 2 structures were studied they were found to lead to deep minima, making CO 2 release much more difficult. A large effort was spent, including investigations of other spin states, varying the number of protons and electrons, adding water, etc., until a plausible pathway for SC bond cleavage was found. In this pathway a water molecule is inserted in between molybdenum and the SCO 2 group. Full catalytic cycles, including electron and proton transfers, are constructed both with and without SC bond formation. When these pathways are extended to two full catalytic cycles it can be understood why the formation of the SC bond actually makes catalysis faster, even though the individual step of CO 2 release becomes much more difficult. These results agree well with experimental findings. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 888–898, 2005