Fig.2.

The filtered image of the front layer of a flattened hexamer tube corresponds to a model surface lattice built of pairs of pentamers arrayed with p2 symmetry. Image A was computed from the diffraction pattern of the portion of the tube boxed in Fig. 1A. The pattern was filtered to include the spots indexed in Fig. 1C and the equator (with the equator and the meridional pair of spots given half weighting). The planar model (B) was built in the computer from regular pen tamers arranged in a p2 lattice at the coordinates measured for the capsomeres in the unit cell of the filtered image. One choice of unit cell is boxed.