Imidazole-Ligated Compound I Intermediates: The Effects of Hydrogen Bonding
- Creators
- Green, Michael T.
Abstract
An unresolved issue of peroxidase activity is the role played by the hydrogen bond between the proximal histidine ligand and a highly conserved aspartate group. It has been postulated that this hydrogen bond imparts imidazolate character to the axial ligand, increasing its donating ability and stabilizing the high valent compound I intermediate. A general feature of biological compound I intermediates is that they display weaker spin couplings than model systems. To understand how the Asp-His hydrogen bond affects the electronic structure of the compound I intermediate and to establish a connection between it and the decreased coupling strengths observed in peroxidases, we have perfomed density functional calculations on imidazole- and imidazolate-ligated perferryl porphyrin species. It was found that the imidazolate compound I intermediate possesses an imidazolate-based radical, while the imidazole compound I intermediate possesses a porphyrin-based radical. Delocalizaton of the radical onto the axial ligand was found to reduce the strength of the spin coupling.
Additional Information
© 2000 American Chemical Society. Received December 15, 1999. Publication Date (Web): September 16, 2000. The author thanks Harry Gray, the Burroughs Wellcome Fund, and the National Institutes of Health for supporting this research.Additional details
- Eprint ID
- 71231
- DOI
- 10.1021/ja994377k
- Resolver ID
- CaltechAUTHORS:20161018-135415365
- Harry B. Gray
- Burroughs Wellcome Fund
- NIH
- Created
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2016-10-18Created from EPrint's datestamp field
- Updated
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2021-11-11Created from EPrint's last_modified field