1. Center for Molecular Modeling, Ghent University, Technologiepark 903, 9052 Zwijnaarde, Belgium, Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE 205, Tampa, Florida 33620-5240, United States, Laboratory of Computational Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States, and Q-Chem Inc., 5001 Baum Blvd, Suite 690, Pittsburgh, Pennsylvania 15213, United States