EM examination of particle assembly of L1 mutant proteins. A) The purified proteins from four different L1 constructs. Lane 1: full-length HPV16 L1; lane 2: D1-L1 deletion mutant of HPV16 L1; lane 3: D2-L1 deletion mutant of HPV16 L1; lane 4: D2-L1 deletion mutant of HPV18 L1. B-E) EM images of the purified proteins treated under assembly condition. The proteins were in incubated in the assembly buffer at 25°C for 30 minutes. Uranyl acetate was then used to treat the protein samples on a carbon grid for EM examination. The scale of the images is indicated by the bar above panel B. The images shown are: (B) full-length HPV16 L1; (C): D1-L1 mutant of HPV16 L1; (D): D2-L1 mutant of HPV16 L1; (E): D2-L1 mutant of HPV18 L1.