TABLE 1.

Effect of incubation at 0°C on the integrity of m100 procapsids and wild-type HSV-1 B-capsids^a

Incubation for 30 min at (°C):	Mean no./electron microscope field ± SD (n)
	m100 procapsids	HSV-1 B capsids
21	120 ± 18 (3)	178 ± 30 (n = 3)
0	4 ± 3 (4)	199 ± 45 (n = 4)

^aThe procedures described in Materials and Methods were used to isolate procapsids from BHK cells infected for 18 h with HSV-1 m100 virus. The procapsid-containing precipitate was resuspended in 100 μl of PBS and divided into two aliquots, which were incubated at room temperature (21°C) or 0°C. Samples were then applied to electron microscope grids, negatively stained with 1% uranyl acetate, and photographed in the electron microscope. Procapsids were counted on electron microscope negatives which were recorded at a magnification of ×8,300. The same analysis was performed with wild-type HSV-1 B capsids which were prepared from infected BHK cells as previously described (27).