Radial Distribution Function for Semiflexible Polymers Confined in Microchannels

TL;DR

This paper derives an analytical expression for the end-to-end distance distribution of semiflexible polymers under confinement, validated by microscopy data, and highlights the importance of considering confinement effects in mechanical property estimation.

Contribution

It provides a new analytical framework for understanding polymer behavior under confinement, including a self-consistent approach for realistic potentials.

Findings

Excellent agreement with microscopy data for actin filaments

Confinement significantly affects estimates of bending rigidity

Neglecting confinement overestimates filament rigidity

Abstract

An analytic expression is derived for the distribution $G(\vec{R})$ of the end-to-end distance $\vec{R}$ of semiflexible polymers in external potentials to elucidate the effect of confinement on the mechanical and statistical properties of biomolecules. For parabolic confinement the result is exact whereas for realistic potentials a self-consistent ansatz is developed, so that $G(\vec{R})$ is given explicitly even for hard wall confinement. The theoretical result is in excellent quantitative agreement with fluorescence microscopy data for actin filaments confined in rectangularly shaped microchannels. This allows an unambiguous determination of persistence length $L_P$ and the dependence of statistical properties such as Odijk's deflection length $\lambda$ on the channel width $D$. It is shown that neglecting the effect of confinement leads to a significant overestimation of bending rigidities for filaments.