1. Department of Medicinal Chemistry, Victorian College of Pharmacy, Monash University (Parkville Campus), 381 Royal Parade, Vic 3052, Australia, Departement de Biologie et Genomique Structurale, IGBMC, CNRS INSERM ULP, 1 rue Laurent Fries, B.P. 163, 67404 Illkirch, France, and Structural Biology Center, Biosciences Division, Argonne National Laboratory, Argonne, Illinois