FIG. 9.

Purified B capsids that had been treated at pH 7.2 (a and b) or pH 5.5 (c and d) as shown in Fig. 8 were loaded onto 13-ml, 10 to 40% (wt/vol) sucrose gradients of the same pH. After centrifugation at 40,000 rpm for 20 min in a Sorvall TsT41 rotor, 10 fractions were collected from the bottom of the gradient. Twenty-microliter samples of each fraction were analyzed on SDS-10% polyacrylamide gels and transferred to nitrocellulose membranes. To reveal the distribution of VP22a, the blots were probed with MCA406 antibody (b and d). The blots were then incubated in a solution containing 100 mM 2-mercaptoethanol, 2% (wt/vol) SDS, and 62.5 mM Tris-HCl (pH 6.7) at 50°C for 30 min to remove bound antibody and reprobed with DM185 antibody to reveal the distribution of the major capsid protein, VP5 (a and c).