1. Rudolf Virchow Center for Experimental Biomedicine; Institute of Structural Biology; University of Würzburg; Josef-Schneider-Straße 2 97080 Würzburg Germany
2. Institute of Pharmacy and Food Chemistry; University of Würzburg; Am Hubland 97074 Würzburg Germany
3. Novartis Institute for Biomedical Research; Novartis Campus 4002 Basel Switzerland
4. Northwestern University; Department of Chemistry, Silverman Hall; Sheridan Road 2145 Evanston 60208 IL USA
5. University of Houston; College of Pharmacy; 4849 Calhoun Road Houston 77204 TX USA