FIG. 6.

Quantitation of Vif in OptiPrep-gradient-purified virions. (A) H9-derived HXB2NEO virions from fraction 13 of the OptiPrep velocity gradient were separated by SDS-PAGE and analyzed by immunoblotting. p24^Gag and Vif-His proteins, shown in nanogram quantities, were run side by side with OptiPrep-velocity-gradient-purified HIV-1 (3,000 ng of p24^Gag) on SDS–12% polyacrylamide PAGE. (B) H9-derived protease mutant (Pr⁻) virions from fraction 13 of the OptiPrep velocity gradient were separated by SDS-PAGE and analyzed by immunoblotting. P55^Gag and Vif-His proteins, shown in nanogram quantities, were run side by side with OptiPrep-velocity-gradient-purified HIV-1 (3,000 ng of p24^Gag) on SDS–12% polyacrylamide PAGE. Protein profiles were analyzed by immunoblotting with anti-HIV-1-positive serum (top panels) and anti-Vif serum (bottom panels).