Spectrophotometric observations relating to the oxidation–reduction potential of cytochrome b in non-phosphorylating heart-muscle particles

Abstract

The equilibrium between the succinate-fumarate system and the bound cytochrome b of the Keilin and Hartree heart-muscle preparation was studied by a spectrophotometric technique. Methods are described by which measurements of extinction include no interference from myoglobin and little contribution from pigments other than cytochrome b. The observations were confined to that portion of the particle-bound cytochrome b which is reducible by succinate. It is suggested that the oxidation-reduction properties of the cytochrome b of the succinic oxidase system of heart muscle are best represented by the mean value for the oxidation-reduction potential, namely +77 mv at pH7 and 25[degree].