1. Department of Chemistry, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235, Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, Texas 77555-1068, and Center for Research on Occupational and Environmental Toxicology, Oregon Health and Science University, 3181 Southwest Sam Jackson Park Road, L606, Portland, Oregon 97239-3098