The use of acetylated ferricytochrome C for the detection of superoxide radicals produced in biological membranes

Acetylation of 60% of lysine residues of horse heart ferricytochrome c results in more than 95% decrease of its ability to be reduced by mitochondrial and microsomal reductases and to become oxidized (after chemical reduction) by mitochondrial oxidase. The ability of acetylated ferricytochrome c to be reduced by 02- radicals is maintained, making this derivative useful for the detection of 02- radicals in biological systems containing cytochrome c reductases or oxidases. Mitochondrial membranes can reduce acetylated ferricytochrome c at a rate of 0.5 nmoles.min-1.mg-1. Such a reaction is 82% inhibited by 2.8 × 10-8M superoxide dismutase. © 1975 Academic Press, Inc.