1. Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, Osaka Prefectural Institute of Public Health, Osaka 537, Japan, Chemistry Department, Xavier Univeristy of Louisiana, New Orleans, Louisiana 70125-1098, Department of Pharmacology, Tulane Univeristy School of Medicine, New Orleans, Louisiana 70112-2699, and Department of Chemistry, Tulane University, New Orleans, Louisiana 70118-5645