1. Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35043 Marburg, Germany
2. Structural Genomics Consortium, Oxford University, Old Road Campus Building, Roosevelt Drive, Oxford, OX3 7DQ, United Kingdom
3. Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United States, and The Wistar Institute, 3601 Spruce Street, Philadelphia, Pennsylvania 19104, United States