Peak Polarogmphy and Electroreduction Mechanism of a Ferriheme Dimer

The electroreduction of aqueous ferriheme was investigated at Kemula's hanging mercury drop electrode. Peak voltammograms were obtained at 9 < pH < 11 using linear potential sweep rates in a range between 0.01 and 10 volt per second. Reduction of ferriheme to ferroheme proceeded via a novel “mixed ferrous-ferric” intermediate whose disproportionation regenerated the initial ferriheme dimer yielding simultaneously equimolar amounts of the ultimate ferroheme dimer product.