X-ray absorption spectroscopy of chloroperoxidase compound I: Insight into the reactive intermediate of P450 chemistry. Journal   Proceedings of the National Academy of Sciences of the United States of America. Citation   Proc Natl Acad Sci U S A. 102(46):16563-5 Publication date   2005 Nov 15 Authors   Stone KL Behan RK Green MT Investigators   Michael Green MeSH headings   Chloride Peroxidase Cytochrome P-450 Enzyme System MeSH qualifiers   chemistry Abstract   We report the structural characterization of a thiolate-ligated ferryl radical. Using x-ray absorption spectroscopy, we examined chloroperoxidase (CPO) compound I (CPO-I). Our results indicate that CPO-I is an authentic ferryl species with an Fe-O bond of 1.65 A. Axial-ligand interactions result in a remarkably long 2.48-A Fe-S bond. Analogous forms of cytochrome P450 and CPO have been shown to possess virtually identical coordination environments. Thus, it seems likely that our findings provide a good structural description of the elusive P450-I.