Local rule mechanism for selecting icosahedral shell geometry

Local rules are given for various virus capsid, or protein shell, geometries. Local rules specify local interaction patterns that can direct the self-assembly of coat and scaffolding subunits into different capsid geometries. They provide a mathematical abstraction allowing combinatorial analysis of possible assembly pathways. Local rules and simulations are provided for a geometry called T = 7 such that a small change in the rules produces an alternate T = 4 geometry. This is intriguing since evidence has been accumulating that some T=7 capsids are closely related to T = 4 capsids. (C) 2000 Elsevier Science B.V. All rights reserved.