Radial distribution of RNA genome packaged inside spherical viruses

TL;DR

This study models the distribution of RNA inside spherical viruses, revealing how RNA concentration varies with capsid attraction strength and correlates with experimental observations.

Contribution

It introduces a model explaining RNA distribution inside spherical viruses based on capsid attraction strength and RNA structure, aligning with experimental data.

Findings

RNA concentration peaks at the center for weak attraction

RNA forms a dense layer near the capsid for strong attraction

RNA packaging correlates with capsid surface area rather than volume

Abstract

The problem of RNA genomes packaged inside spherical viruses is studied. The viral capsid is modeled as a hollowed sphere. The attraction between RNA molecules and the inner viral capsid is assumed to be non-specific and occurs at the inner capsid surface only. For small capsid attraction, it is found that monomer concentration of RNA molecules is maximum at the center of the capsid to maximize their configurational entropy. For stronger capsid attraction, RNA concentration peaks at some distance near the capsid. In the latter case, the competition between the branching of RNA secondary struture and its adsorption to the inner capsid results in the formation of a dense layer of RNA near capsid surface. The layer thickness is a slowly varying (logarithmic) function of the capsid inner radius. Consequently, for immediate strength of RNA-capsid interaction, the amount of RNA packaged inside a virus is proportional to the capsid {\em area} (or the number of proteins) instead of its volume. The numerical profiles describe reasonably well the experimentally observed RNA nucleotide concentration profiles of various viruses.