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Single Crystal EPR Studies of the Reduced Active Site of [NiFe] Hydrogenases from Desulfovibrio vulgaris Miyazaki F.
- Source :
-
Journal of the American Chemical Society . 1/8/2003, Vol. 125 Issue 1, p83. 11p. 5 Diagrams, 4 Charts, 4 Graphs. - Publication Year :
- 2003
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Abstract
- In the catalytic cycle of [NiFe] hydrogenase the paramagnetic Ni-C intermediate is of key importance, since it is believed to carry the substrate hydrogen, albeit in a yet unknown geometry. Upon illumination at low temperatures, Ni-C is converted to the so-called Ni-L state with markedly different spectroscopic parameters. It is suspected that Ni-L has lost the "substrate hydrogen". In this work, both paramagnetic states have been generated in single crystals obtained from the [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F. Evaluation of the orientation dependent spectra yielded the magnitudes of the g tensors and their orientations in the crystal axes system for both Ni-C and Ni-L. The g tensors could further be related to the atomic structure by comparison with the X-ray crystallographic structure of the reduced enzyme. Although the gtensor magnitudes of Ni-C and Ni-L are quite different, the orientations of the resulting g tensors are very similar but differ from those obtained earlier for Ni-A and Ni-B (Trofanchuk et al. J. Biol. Inorg. Chem. 2000, 5, 36-44). The g tensors were also calculated by density functional theory (DFT) methods using various structural models of the active site. The calculated g tensor of Ni-C is, concerning magnitudes and orientation, in good agreement with the experimental one for a formal Ni(III) oxidation state with a hydride (H-) bridge between the Ni and the Fe atom. Satisfying agreement is obtained for the Ni-L state when a formal Ni(I) oxidation state is assumed for this species with a proton (H[sup +]) removed from the bridge between the nickel and the iron atom. [ABSTRACT FROM AUTHOR]
- Subjects :
- *HYDROGENASE
*HYDROGEN
*SPECTRUM analysis
Subjects
Details
- Language :
- English
- ISSN :
- 00027863
- Volume :
- 125
- Issue :
- 1
- Database :
- Academic Search Index
- Journal :
- Journal of the American Chemical Society
- Publication Type :
- Academic Journal
- Accession number :
- 9020289
- Full Text :
- https://doi.org/10.1021/ja027522u