Ammonia displaces methanol bound to the water oxidizing complex of photosystem II in the S2 state

Ammonia and methanol both bind to the water oxidising complex of photosystem II during its turnover, possibly at sites where water binds during the normal water oxidation process. We have investigated the interaction between these two water analogues at the S-2 state of the water oxidising cycle using electron magnetic resonance techniques. We find evidence that ammonia displaces methanol from its binding site. (c) 2005 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.