Purification and Characterization of Pseudovirus

VSVΔG/GFP-G* or VSVΔG/GFP-Gα* pseudovirus was purified through a sucrose cushion as described before. Virus was prepared as described before [39] (link). Briefly, pelleted virus was resuspended in 50 mM Tris-HCl, pH 7.5 with 100 mM NaCl buffer or in 50 mM MOPS, pH 6.6 with 100 mM NaCl buffer. The pH 6.6 dissolved virus was incubated for 15 min at 37°C and subsequently dialyzed at room temperature against 50 mM MOPS, pH 5.5 with 100 mM NaCl buffer for 30 min. The virus preps (pH 7.5 and pH 5.5) were adsorbed onto a discharged carbon film and subjected to negative staining (2% uranyl acetate solution). Probes were analyzed with a Philips CM200 microscope at 100 kV.