Free radical reduction of fericytochrome-C

Rate constants have been determined for the reduction of ferricytochrome-c by free radicals. k values for pyridinyl radicals, benzoate adduct radicals, nitrobenzene and nitrobenzoate anion radicals, α-hydroxy radicals, formyl anion radical, and superoxide radical show no apparent correlation with size, charge, or structure of the reductant. Some k values change as the pH is increased. The methyl viologen radical is the most reactive; 1-methyl nicotinamide, NAD; is reactive; the pentaerythritol radical is unreactive at pH = 7 but moderately reactive at pH = 9; and 02- becomes less reactive with increasing pH. The results indicate that several mechanisms for electron transfer are operative and that conformers of differing reactivity influence the kinetics in alkaline solutions