1. Max-Planck Institut für Kolloid- und Grenzflächenforschung, Rudower Chaussee 5, D-12489 Berlin, Germany, St. Petersburg State University, Institute of Chemistry, Universitetskiy pr. 2, St.-Petersburg, 198904 Russia, Department of Physical Chemistry, University of Sofia, 1 J. Bourchier Ave., 1126 Sofia, Bulgaria, and Virchov-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany