Electrochemical reduction of pheophytin and its participation in the functioning of photosystem II

Abstract The effect of medium acidity on the mechanism of the electrochemical reduction of pheophytin at the mercury dropping electrode has been studied. The rate of anion-radical protonation is shown to be comparable with the rate of electron transfer. It leads to an experimentally observed complex dependence of E 1 2 on pH. The products of pheophytin reduction as well as their oxidation potentials have been identified. On the basis of the data obtained, a possible mechanism of pheophytin participation in the functioning of photosystem II is discussed.