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Imidazole-Ligated Compound I Intermediates: The Effects of Hydrogen Bonding

Green, Michael T. (2000) Imidazole-Ligated Compound I Intermediates: The Effects of Hydrogen Bonding. Journal of the American Chemical Society, 122 (39). pp. 9495-9499. ISSN 0002-7863.

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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.

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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.
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Burroughs Wellcome FundUNSPECIFIED
Record Number:CaltechAUTHORS:20161018-135415365
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Official Citation:Imidazole-Ligated Compound I Intermediates:  The Effects of Hydrogen Bonding Michael T. Green Journal of the American Chemical Society 2000 122 (39), 9495-9499 DOI: 10.1021/ja994377k
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71231
Deposited By: George Porter
Deposited On:18 Oct 2016 21:15
Last Modified:18 Oct 2016 21:15

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