Western blot of fractionated sucrose gradients (fractions 1 to 20, 5-to-20% gradient) of the procapsid band purified in CsCl gradients. (a) Membrane probed with anti-Syn5 antibodies. Syn5, purified infectious particles (control). Fractions 10 to 12 contain the 240 S peak, and fractions 15 to 17 the 340 S peak. (b) Membrane probed with anti-scaffold serum. Scaff. (1), 40-kDa scaffolding protein band; scaff. (2), faint 29-kDa scaffolding band; M, protein standard.