1. Department of Pharmaceutical Sciences, School of Pharmacy, University of Southern California, 1985 Zonal Avenue, Los Angeles, California 90089, Accelrys, Inc., 9685 Scranton Rd., San Diego, California 92121, Laboratory of Antiviral Drug Mechanisms, SAIC-Frederick, Frederick, Maryland 21702, and Screening Technologies Branch, DTP, DCTD, National Cancer Institute at Frederick, Frederick, Maryland 21702