1. Pharmaceutical and Medicinal Chemistry, Saarland University, P.O. Box 151150, D-66041 Saarbrücken, Germany
2. Unité de Biochimie Structurale (CNRS-URA 2185), Institut Pasteur, F-75724 Paris, France
3. Department of Internal Medicine I, University of Frankfurt, Theodor-Stern-Kai 7, D-60590 Frankfurt a.M., Germany