... Center, Burnett College of Biomedical Sciences at University of Central Florida,Orlando, FL, USA2 Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, ... function of glycoprotein 41 (gp41) of HIV-1 [12,13]. Retrocyclin prevented formation of thesix-helix bundle (6HB) of in vitro synthesized heptadrepeat 1 (HR1) and heptad repeat 2 (HR2) regions of gp41 ... diversity indices of HR1 and HR2 are distinctlydissimilar (Fig. 1A). The majority of sites (28 of 36)on HR1 are monomorphic and do not readily change,whereas the majority of sites (21 of 34) on HR2...