An automated procedure was developed to determine the geometrical and chemical interactions of crystalline virus particles using the crystal parameters, particle position, orientation, and atomic coordinates for an icosahedral asymmetric unit.

Two applications of the program are reported: (1) An analysis of a novelpseudo-rhombohedral (R32) symmetry present in the monoclinic crystal lattices of both Nodamura Virus (NOV) and Coxsackie virus B3 (CVB3). The study shows that in both cases the interactions between particles is substantially increased by minor deviations from exact R32 symmetry and that only particles with the proper ratio of dimensions along twofold and fivefold symmetry axes (such as southern bean mosaic virus) can achieve comparable buried surface area in the true R32 space group.