Viral self-assembly as a thermodynamic process

TL;DR

This paper presents a thermodynamic model explaining why viral capsids adopt icosahedral symmetry, showing it depends on internal protein configurations rather than free energy minimization alone.

Contribution

It introduces a statistical thermodynamic framework revealing the necessity of internal protein states for icosahedral symmetry in viral capsids.

Findings

Icosahedral symmetry is not expected from identical subunits without internal switches.

Two internal configurations are required for icosahedral symmetry.

Symmetry depends on internal structural parameter optimization.

Abstract

The protein shells, or capsids, of all sphere-like viruses adopt icosahedral symmetry. In the present paper we propose a statistical thermodynamic model for viral self-assembly. We find that icosahedral symmetry is not expected for viral capsids constructed from structurally identical protein subunits and that this symmetry requires (at least) two internal "switching" configurations of the protein. Our results indicate that icosahedral symmetry is not a generic consequence of free energy minimization but requires optimization of internal structural parameters of the capsid proteins.