1. Manchester Interdisciplinary Biocentre (MIB), The University of Manchester, 131 Princess street, Manchester M1 7ND, UK, Institute for Tropical Medicine, Department of Parasitology, University of Tübingen, Wilhelmstr. 27, 72074 Tübingen, Germany, and Department of Pharmaceutical Chemistry, University of Kiel, Gutenbergstrasse 76, Kiel, Germany