1. Department of Chemistry, Binghamton University, 4400 Vestal Parkway East, Binghamton, New York 13850, Department of Physiology and Biophysics, University of Miami School of Medicine, 1600 NW 10th Avenue, Miami, Florida 33136, and Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520-8066