FIG. 1.

Negative staining EM of the HSV-1 UL6 portal protein. (a) Field of UL6 molecules, prepared as described previously (16), and negatively stained with uranyl acetate. Bar, 200 Å. Round particles likely to represent axial views (a few examples are marked with asterisks) were analyzed with the symmetry detection algorithm, Rotastat (12), which detected 11-fold, 12-fold, 13-fold, and less strongly, 14-fold molecules (see Results). When the images were classified in terms of their strongest harmonics, they were estimated to be 23% 11-mers, 27% 12-mers, 22% 13-mers, and 16% 14-mers. Correlation-averaged images of molecules presenting the first three symmetries are shown in panels b, c, and d. Their resolutions were 28 Å for panel b and 26 Å for both panels c and d. These images were further enhanced by rotational symmetrization in panels e, f, and g. The 14-mers were not only fewer but appeared less regular, to judge by the symmetry detection analysis and markedly lower resolution achieved on averaging (data not shown). Bar, 100 Å.