Changes in the spin state and reactivity of cytochrome C induced by photochemically generated singlet oxygen and free radicals.

This work compares the effect of photogenerated singlet oxygen (O(2)((1)Delta(g))) (type II mechanism) and free radicals (type I mechanism) on cytochrome c structure and reactivity. Both reactive species were obtained by photoexcitation of methylene blue (MB(+)) in the monomer and dimer forms, respectively. The monomer form is predominant at low dye concentrations (up to 8 microm) or in the presence of an excess of SDS micelles, while dimers are predominant at 0.