Possible intermediates in the mechanism of dihydrogen activation by the nickel-iron center of Ni-Fe hydrogenases, as proposed by Dole et al. (Dole, F.; Fournel, A.; Magro, V.; Hatchikian, E. C.; Bertrand, P.; Guigliarelli, B. Biochemistry 1997, 36, 7847-7854), have been investigated using quantum chemical methods. Results obtained on models of the Ni-A, Ni-B, Ni-SI, Ni-C, and Ni-R forms of the enzyme show that (i) despite valence state changes of the nickel ion, the electron density on this metal is very similar in all these forms, (ii) in paramagnetic species, the spin density is mainly localized on the nickel atom and its sulfur ligands, which confirms the diamagnetic nature of the iron ion in the [Ni-Fe] cluster, (iii) in the Ni-C and Ni-R states, a hydrogen atom can bridge the two metal ions without major structural reorganization, apart from a shortening of the Ni-Fe distance, which becomes equal to 2.67 Angstrom. The good agreement between these results and the experimental data obtained on hydrogenases supports the active site structures proposed by Dole et al. for the various states of the enzyme.
DE GIOIA, L., Fantucci, P., Guigliarelli, B., Bertrand, P. (1999). Ni-Fe hydrogenases: A density functional theory study of active site models. INORGANIC CHEMISTRY, 38(11), 2658-2662 [10.1021/ic9811446].
Ni-Fe hydrogenases: A density functional theory study of active site models
DE GIOIA, LUCA;FANTUCCI, PIERCARLO;
1999
Abstract
Possible intermediates in the mechanism of dihydrogen activation by the nickel-iron center of Ni-Fe hydrogenases, as proposed by Dole et al. (Dole, F.; Fournel, A.; Magro, V.; Hatchikian, E. C.; Bertrand, P.; Guigliarelli, B. Biochemistry 1997, 36, 7847-7854), have been investigated using quantum chemical methods. Results obtained on models of the Ni-A, Ni-B, Ni-SI, Ni-C, and Ni-R forms of the enzyme show that (i) despite valence state changes of the nickel ion, the electron density on this metal is very similar in all these forms, (ii) in paramagnetic species, the spin density is mainly localized on the nickel atom and its sulfur ligands, which confirms the diamagnetic nature of the iron ion in the [Ni-Fe] cluster, (iii) in the Ni-C and Ni-R states, a hydrogen atom can bridge the two metal ions without major structural reorganization, apart from a shortening of the Ni-Fe distance, which becomes equal to 2.67 Angstrom. The good agreement between these results and the experimental data obtained on hydrogenases supports the active site structures proposed by Dole et al. for the various states of the enzyme.
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