Direct observation of the tube model in F-actin solutions

TL;DR

This study directly visualizes the tube model in F-actin solutions, confirming predicted scaling laws and revealing an exponential distribution of tube curvatures due to transient entropic trapping.

Contribution

First direct imaging of confinement tubes in F-actin solutions, validating the tube model and uncovering new insights into tube curvature distributions.

Findings

Average tube width follows predicted scaling behavior

Tube curvature distribution is exponential

Transient entropic trapping influences filament confinement

Abstract

Mutual uncrossability of polymers generates topological constraints on their conformations and dynamics, which are generally described using the tube model. We imaged confinement tubes for individual polymers within a F-actin solution by sampling over many successive micrographs of fluorescently labeled probe filaments. The resulting average tube width shows the predicted scaling behavior. Unexpectedly, we found an exponential distribution of tube curvatures which is attributed to transient entropic trapping in network void spaces.