Role of Reversibility in Viral Capsid Growth: A Paradigm for Self-Assembly

Self-assembly at submicroscopic scales is an important but little understood phenomenon. A prominent example is virus capsid growth, whose underlying behavior can be modeled using simple particles that assemble into polyhedral shells. Molecular dynamics simulation of shell formation in the presence of an atomistic solvent provides new insight into the self-assembly mechanism, notably that growth proceeds via a cascade of strongly reversible steps and, despite the large variety of possible intermediates, only a small fraction of highly bonded forms appear on the pathway.

Figure 1

Model particle and the effective truncated pyramidal shape; small spheres denote interaction sites.

Figure 2

Cluster size distributions as functions of time (MD units); the distributions, including monomers, are expressed as mass fractions, and $e$ (attraction strength) values are selected to show the different growth scenarios.

Figure 3

Snapshot of the $e=0.13$ system with 80 complete shells; solvent atoms are shown semitransparently, and there are visual artifacts (closed shells that appear open and particles protruding through walls) due to periodic boundaries.

Figure 4

Fraction of events producing unit size increases and decreases, increases greater than unity, and others; mean cluster lifetimes (MD units).