1. Organic Chemistry, Department of Chemistry, Faculty of Mathematics, Informatics and Natural Sciences, Universität Hamburg, Martin-Luther-King-Platz 6, Hamburg D-20146, Germany
2. Laboratory of Virology and Chemotherapy, Department of Microbiology and Immunology and Transplantation, Rega Institute for Medical Research, KU Leuven, Herestraat 49, Leuven B-3000, Belgium
3. Centre for Structural Systems Biology (CSSB), Hamburg, DESY Campus, Notkestrasse 85, Hamburg D-22607, Germany