1. Department of Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, S-221 00 Lund, Sweden, Atomistix A/S, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark, and Biostructural Research Group, The Danish University of Pharmaceutical Sciences, Universitetsparken 2, DK-2200 Copenhagen Ø, Denmark