Fig. 4.

Incorporation of 9b protein into purified SARS-CoV virions. Clarified supernatant from SARS infected cells was subjected to 20% sucrose ultracentrifugation. The pellets resuspended in NTE buffer were further applied on a 20–60% sucrose gradient cushion. Twelve fractions were collected from top to bottom after ultracentrifugation, each fraction was condensed using 20% sucrose and subjected to Western blot analysis with anti-S monoclonal antibody (S), anti-N monoclonal antibody (N), anti-M polyclonal antibody (M) and anti-9b monoclonal antibody (9b). β-actin was detected by actin specific polyclonal antibody (Actin). The density of each fraction was measured and is shown.