  Understanding how highly symmetric, robust, monodisperse protein cages
self-assemble can have major applications in various areas of
bio-nanotechnology, such as drug delivery, biomedical imaging and gene therapy.
We develop a model to investigate the assembly of protein subunits into the
structures with different size and symmetry. Using Monte Carlo simulation, we
obtain the global minimum energy structures. Our results suggest that the
physical properties of building blocks including the spontaneous curvature,
flexibility and bending rigidity of coat proteins are sufficient to predict the
size of the assembly products and that the symmetry and shape selectivity of
nano-cages can be explained, at least in part, on a thermodynamic basis. The
polymorphism of nano-cages observed in vitro assembly experiments are also
discussed.
