Mechanism for the assembly of spherical viruses: A geometrical approach

A geometrical pathway for the assembly of spherical viruses is described. The proposed pathway involves capsomeres as early intermediates and a cubic closely packed crystal made of capsomeres as a second intermediate. The crystal is then triggered to collapse to form individual virion particles. Only limited patterns of collapse are feasible, thus leading to well defined classes of spherical viruses, all of them found in nature. The mechanism also implies that the large spherical viruses should contain a series of smaller shells as inner cores, the nucleic acid sandwiched between two of them.