Copyright © 2005 Hindawi Publishing Corporation. This is an open access article distributed under the
Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
A vital constituent of a virus is its protein shell, called the viral capsid, that encapsulates and hence protects the viral genome. The surface structures of a large number of icosahedral viruses can be modelled via Caspar-Klug Theory, which has hence become one of the fundamental concepts in virology. However, growing experimental evidence have shown that a significant fraction of viruses falls out of the remit of this theory. Among them are the Papovaviridae, which are of particular interest for the medical sector as they contain cancer causing viruses. A novel approach for the prediction of the protein stoichiometry and bonding structure of icosahedral viruses based on tiling theory is discussed here. It generalises Caspar-Klug Theory, and is in particular applicable also to Papovaviridae. Besides describing the surface structures of the viruses, this approach also provides a tool for the classification of cross-linking structures and the construction of assembly models.