1. Department of Chemistry, Gonzaga University, 502 East Boone Avenue, Spokane, Washington 99258, Department of Chemistry, Colgate University, 13 Oak Drive, Hamilton, New York 13346, Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, Florida 32610, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, Washington 98109, and Department of Molecular and Cellular Biology, University of California, Davis, California 95616