1. Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
2. Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544, USA.
3. Department of Chemistry and Biochemistry, The University of Texas at El Paso, El Paso, TX 79968, USA.
4. Department of Biochemistry and Molecular Pharmacology, Grossman School of Medicine, New York University, New York, NY 10016, USA.
5. New Mexico Consortium, Los Alamos, NM 87545, USA.
6. National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun 130012, China.