The pH-Induced Transition of Iodinated Ferricytochrome c: Electron Paramagnetic Resonance and Absorption Spectra

The heme-associated, pH-induced transition in iodinated ferricytochrome c has been studied by electron paramagnetic resonance (E.P.R.) and absorption spectroscopy. The conversion from type III to type IV (as defined by Theorell, H., and Åkesson, Å.: J. Am. Chem. Soc. 63, 1812 (1941)) ferricytochrome c forms was dramatically altered by iodination of tyrosyl residues. Both absorption and E.P.R. spectra suggested that a transition between similar …