Rigidity-induced scale invariance in polymer ejection from capsid

TL;DR

This study investigates how polymer rigidity influences ejection dynamics from capsids, revealing a phase transition-like crossover from exponential to scale-invariant behavior and establishing a new scaling law for rigid polymers.

Contribution

It provides the first detailed characterization of semiflexible polymer ejection dynamics, highlighting the role of rigidity as a control parameter and discovering a universal scaling law.

Findings

Ejection force does not directly relate to velocity for semiflexible polymers.

A crossover from exponential to scale-invariant ejection dynamics occurs with increasing rigidity.

Ejection time scales as $t(s) \\propto N_0^{0.55} s^{1.33}$ for rigid polymers.

Abstract

While the dynamics of a fully flexible polymer ejecting a capsid through a nanopore has been extensively studied, the ejection dynamics of semiflexible polymers has not been properly characterized. Here we report results from simulations of ejection dynamics of semiflexible polymers ejecting from spherical capsids. Ejections start from strongly confined polymer conformations of constant initial monomer density. We find that, unlike for fully flexible polymers, for semiflexible polymers the force measured at the pore does not show a direct relation to the instantaneous ejection velocity. The cumulative waiting time $t(s)$, that is, the time at which a monomer $s$ exits the capsid the last time, shows a clear change when increasing the polymer rigidity $\kappa$. Major part of an ejecting polymer is driven out of the capsid by internal pressure. At the final stage the polymer escapes the capsid by diffusion. For the driven part there is a cross-over from essentially exponential growth of $t$ with $s$ of the fully flexible polymers to a scale-invariant form. In addition, a clear dependence of $t$ on $N_0$ was found. These findings combined give the dependence $t(s) \propto N_0^{0.55} s^{1.33}$ for the strongly rigid polymers. This cross-over in dynamics where $\kappa$ acts as a control parameter is reminiscent of a phase transition. This analogy is further enhanced by our finding a perfect data collapse of $t$ for polymers of different $N_0$ and any constant $\kappa$.