1. Intramural Research Support Program, SAIC Frederick, and Chemistry Section, Laboratory of Comparative Carcinogenesis, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland 21702, Department of Chemistry, George Mason University, Fairfax, Virginia 22030, Division of Hematology and Yerkes Regional Primate Research Center, Emory University, Atlanta, Georgia 30322, and Department of Anaesthesia, Massachusetts General Hospital, Boston, Massachusetts 02114