Continuous sucrose gradient analysis of virus-like particles. Cells were transfected with pCAGGS/F-cmyc, pCAGGS/G-FLAG, and pCAGGS/M and processed as described for VLP isolation as described in methods. The resuspended pellet from the 10% (w/v) sucrose cushion was applied to a 10-60% (w/v) continuous sucrose gradient. After centrifugation the gradient was fractionated, and each fraction analysed by immunoblotting with (A) anti-cmyc, (B) anti-FLAG and (C) anti-M. The various G, F and M protein species are indicated, as are the peak fractions (*). 1 is the top fraction and 12 the bottom fraction.