title: Extended X-ray absorption fine structure studies of cytochromes c: structural aspects of oxidation-reduction.
abstract: EXAFS fluorescence spectra were recorded for high-potential c-type cytochromes which range in oxidation-reduction potential from +145 to +365 mV. No average Fe-ligand bond length differences greater than 0.03 A were observed, for any cytochrome source of oxidation state. Least-squares analysis in combination with model calculations allowed limits to be set on the average Fe-N bond length (1.97-1.99 A) and the Fe-S bond length (2.29-2.32 A). A change of 0.05 A in either the average Fe-N or the Fe-S bond length is readily detectable with the range and quality of the data presented here. Two major conclusions are drawn from this study: In octahedrally coordinated iron porphyrin systems, Fe-N and Fe-S bond lengths are independent of oxidation-reduction potential, and they are also independent of oxidation state. A model for the regulation of oxidation-reduction potential in cytochrome c is proposed.
mesh_terms: D000818:Animals; D003574:Cytochrome c Group; D008956:Models, Chemical; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction; D013052:Spectrometry, X-Ray Emission; D014413:Tuna / Q000378:metabolism
chemical_list: D003574:Cytochrome c Group