1. Biota Chemistry Laboratory, School of Chemistry, Monash University, PO Box 23 Victoria, Australia 3800; Biota Virology Laboratory, Microbiology Department, Monash University, Clayton Victoria, 3800; Biota Holdings, Level 4, 616 St Kilda Road, Melbourne, Victoria, Australia 3004; and Institute for Antiviral Research, Utah State University, Logan, Utah 84322-5600