On the Redox Potentials of Ubiquinone and Cytochrome b in the Respiratory Chain

Abstract

The standard redox potential of ubiquinone in submitochondrial particles is measured by equilibration with the succinate/fumarate system to about 65 mV at pH 7, with the redox ratio, n= 2. The pH dependence is ‐60 mV/Δ pH. The lower value measured for bound ubiquinone is discussed in comparison with the value found for isolated ubiquinone (104 to 112 mV, pH 7) determined in ethanol‐HCl. In parallel experiments the standard redox potential of cytochrome b was measured to 72.5mV at pH 7. The pH dependence is ΔE/Δ pH = 0 at pH < 6.8 and ‐ 60 mV ΔHp at pH > 6.8. Copyright © 1969, Wiley Blackwell. All rights reserved