Compression and stretching of a self-avoiding chain in cylindrical nanopores

TL;DR

This study investigates how a self-avoiding chain behaves under compression and stretching inside cylindrical nanopores, revealing scaling laws and analytical relations useful for understanding biomolecular confinement.

Contribution

The paper introduces new scaling relations and an analytical force-extension model for self-avoiding chains in cylindrical confinement, validated through simulations and analysis.

Findings

Confirmed a scaling relation $-f \, D \, \sim R^{-9/4}$ in strong compression.

Derived a force-extension relation for weak deformations: $f \, D = -A(R/R_0) + B (R/R_0)^{-2}$.

Developed a universal analytical relation for strong stretching regimes.

Abstract

Force-induced deformations of a self-avoiding chain confined inside a cylindrical cavity, with diameter $D$, are probed using molecular dynamics simulations, scaling analysis, and analytical calculations. We obtain and confirm a simple scaling relation $-f \cdot D \sim R^{-9/4}$ in the strong-compression regime, while for weak deformations we find $f \cdot D = -A(R/R_0) + B (R/R_0)^{-2}$, where $A$ and $B$ are constants, $f$ the external force, and $R$ the chain extension (with $R_0$ its unperturbed value). For a strong stretch, we present a universal, analytical force-extension relation. Our results can be used to analyze the behavior of biomolecules in confinement.