1. Abt. Biophysik, FB. Biologie/Chemie, Universität Osnabrück, D-49069 Osnabrück, Germany, A. N. Frumkin Institute of Electrochemisty, Russian Academy of Sciences, Moscow 117071, Russia, and A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 118899, Russia