FIG. 2.

Analysis of virus particles by sucrose velocity gradient centrifugation. (A) Authentic pseudotyped LLRNL virus prepared by conventional methods from 293GP/LLRNL cells. (B) Untreated gag-pol RNA particles and gag-pol RNA particles made infectious by exposure to VSV-G for which 0.5-ml volumes of conditioned medium of 293 cells transfected with pCMV-G and of 293GP/LLRNL cells were mixed and centrifuged at 24,000 rpm at 4°C in Beckman SW28 rotor for 90 min. Pellets were resuspended with 1 ml of PBS and loaded onto the sucrose gradients. (C) Western blot analysis of VSV-G in gradient fractions containing the media from 293 cells transfected with pCMV-G, authentic mature pseudotyped LLRNL virus, and gag-pol RNA particles from 293GP/LLRNL cells made infectious by treatment with VSV-G as described above. RLU, relative luciferase units.