Constraint Release for Reptating Filaments in Semiflexible Networks Depends on Background Fluctuations.

Tina Händler,David M Smith,Cary Tutmarc,Jessica S Freitag,Jörg Schnauß

doi:10.3390/polym14040707

Abstract

Entangled semiflexible polymer networks are usually described by the tube model, although this concept has not been able to explain all experimental observations. One of its major shortcomings is neglecting the thermal fluctuations of the polymers surrounding the examined test filament, such that disentanglement effects are not captured. In this study, we present experimental evidence that correlated constraint release which has been predicted theoretically occurs in entangled, but not in crosslinked semiflexible polymer networks. By tracking single semiflexible DNA nanotubes embedded both in entangled and crosslinked F-actin networks, we observed different reptation dynamics in both systems, emphasizing the need for a revision of the classical tube theory for entangled polymer solutions.

Highlights

Solutions of semiflexible polymers have been studied for decades and are important in soft matter physics, biology and material science, there is still no theoretical model that sufficiently explains their unique properties [1,2]
We were able to verify differences in reptation behavior of semiflexible DNA tracers in entangled and crosslinked F-actin networks; providing experimental verification for the predicted correlated constraint release in fluid semiflexible polymer networks, which is not expected in frozen semiflexible polymer networks [20]
Constraint Release in Entangled F-Actin Networks With our experimental system, we were able to examine the prediction about different constraint release mechanisms in crosslinked and entangled semiflexible polymer networks made by Lang and Frey [20]

Summary

Introduction

Solutions of semiflexible polymers have been studied for decades and are important in soft matter physics, biology and material science, there is still no theoretical model that sufficiently explains their unique properties [1,2]. The most successful approach is an extrapolation of the so-called tube model, which was originally developed to describe solutions of flexible polymers [3,4]. It reduces the many-body problem to a few degrees of freedom by investigating a test filament which is constrained in its motion by all other polymers of the network [1,3–9], see Figure 1a. A recent Brownian dynamics study investigated the effects of constraint release mechanisms in fluid and frozen semiflexible polymer networks and predicted different dynamics of test filaments within these solutions [20]. With the recently established approach to study polymer physics by using DNA nanotechnology [16,17,19], we were able to investigate the proposed differences in constraint release. We used semiflexible DNA nanotubes and tracked their motion in entangled—resembling fluid—or crosslinked—resembling frozen—F-actin networks, see Figure 1a

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Discussion

Conclusion