The co-expression of the F, G and M proteins leads to the formation of virus-like particles (VLPs). Cells were either transfected with (A, B, C) pCAGGS/F-cmyc, pCAGGS/G-FLAG, pCAGGS/M) or (D, E, F) pCAGGS (mock-transfected) and processed for VLPs as described in Methods. The clarified material was applied to a discontinuous gradient composed of 20% (w/v) sucrose, 50% (w/v) sucrose and 60% (w/v) sucrose. The material at the (1) 0-20%, (2) 20-50% and (3) 50-60% interfaces were harvested, together with the material at the bottom of the centrifuge tube (4). This material was analysed by immunoblotting (IB) with (A, D) anti-cmyc, (B, E) anti-FLAG and (C, F) anti-M. The various G, F and M protein species are indicated.