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Ab initio investigation of the structural and electronic differences between active‐site models of [NiFe] and [NiFeSe] hydrogenases
Author(s) -
De Gioia L.,
Fantucci P.,
Guigliarelli B.,
Bertrand P.
Publication year - 1999
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1999)73:2<187::aid-qua12>3.0.co;2-x
Subject(s) - hydrogenase , electronic structure , active site , ab initio , chemistry , nickel , computational chemistry , crystallography , hydrogen , enzyme , organic chemistry , biochemistry
The structural and electronic differences between coordination compounds which model [NiFe] and [NiFeSe] hydrogenase active sites were investigated using quantum chemical methods. A previous study showed that the structural and electronic properties of these model compounds are largely consistent with available experimental data in the case of [NiFe] hydrogenases (L. De Gioia, P. Fantucci, B. Guigliarelli, P. Bertrand, submitted). The extension of this study to models of the NiB, NiSI, NiC, and NiR states of [NiFeSe] hydrogenases show that (i) a hydrogen atom can bridge the two metal centers in the NiC and NiR states of [NiFeSe] hydrogenases and (ii) the structure and electronic features of [NiFeSe] models are in good agreement with available experimental data, except for the NiB model for which the analysis of the spin‐density distribution suggests that a bridging oxygen species is still present. In addition, (iii) the similarity between the structural and electronic properties of the [NiFe] and [NiFeSe] models suggests that the activity differences observed between the two kinds of hydrogenases cannot be attributed to the S→Se substitution alone, (iv) analysis of frontier orbitals strongly suggests that dihydrogen interacts with the Ni center in the initial step of its activation, and (v) the optimized models of the NiR state of [NiFe] and [NiFeSe] enzymes are characterized by an unusual NiHS bridge and lie about 25 kcal/mol lower in energy when compared to the unbridged structure. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 187–195, 1999