1. Institute of Medical Microbiology, University of Zurich, Gloriastrasse 32, CH-8006 Zurich, Switzerland, Institute of Physical Biochemistry, University of Witten/Herdecke, Stockumer Strasse 10, 58448 Witten, Germany, Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, 37077 Goettingen, Germany, and Petersburg Nuclear Physics Institute, Russian Academy of Science, 188300 Gatchina, Russia