1. The CRC Biomolecular Structure Unit, The Institute of Cancer Research, Sutton, Surrey SM2 5NG, U.K., Chemistry Department, University of Auckland, Auckland, New Zealand, Department of Chemistry, Georgia State University, Atlanta, Georgia 30303, Department of Pathology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, and Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, Alabama 36849