1. Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York 11794, Biology Department, Brookhaven National Laboratory, Upton, New York 11973, Department of Physiology and Biophysics, State University of New York at Stony Brook, Stony Brook, New York 11794, Institute for Antiviral Research, Utah State University, Logan, Utah 84322-5600, and Graduate Group in Biophysics, University of California at San Francisco, San Francisco, California 94143