Determination of Formal Potentials of Multihemoprotein, Cytochrome c3 by 1H Nuclear Magnetic Resonance

Macroscopic redox potentials of tetrahemoprotein, cytochrome c3 from D. vulgaris, Miyazaki strain, were derived from 400 MHz 1H NMR measurements. The formal potential, E1o′, was determined to be −0.245±0.005 V vs. NHE compared with a value of −0.240 V obtained electrochemically. The distributions of the intermediate states from the NMR spectra during a redox titration are in good agreement with those previously determined by electrochemistry.