1. Department of Chemistry, University of New Mexico, Albuquerque, New Mexico 87131, Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, 9600 Gudelsky Drive, Rockville, Maryland 20850, and Molecular Structure Unit, Laboratory of Neurotoxicology, NIMH, Building 10, Room 3N309, 10 Center Drive, MSC 1262, Bethesda, Maryland 20892-1262