The temperature dependence of the MCD spectrum of horseradish peroxidase compound I |
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Authors: | W R Browett Z Gasyna M J Stillman |
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Affiliation: | Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7 |
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Abstract: | The magnetic circular dichroism spectrum of the compound I species of horseradish peroxidase, which contains an iron (IV) porphyrin pi-cation radical complex, has been measured between 273 K and 4.2 K. The spectrum is temperature independent between 273 K and 30 K. However, very strong temperature dependence is observed below 30 K. These data do not appear to fit the temperature dependence expected for the presence of a simple MCD C term, or combination of C terms, but suggest that an increase in the coupling between the S = 1 iron (IV), and the S = 1/2 porphyrin pi-cation radical occurs forming a degenerate ground state. This increase in coupling below 30 K may be the result of a phase change in the protein which in turn affects the electronic structure of the heme group. |
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Keywords: | Address correspondence to this author |
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