Microtubule dynamics depart from wormlike chain model

TL;DR

This study reveals that microtubule shape fluctuations deviate from the wormlike chain model for lengths under 10 micrometers, due to complex bending stiffness and internal friction effects.

Contribution

It demonstrates a length-dependent deviation from the wormlike chain model in microtubules, linked to their molecular architecture and internal friction.

Findings

Relaxation times scale with length squared for microtubules under 10 μm.

Bending stiffness varies with length, affecting fluctuation dynamics.

Internal friction influences fluctuations in microtubules shorter than 5 μm.

Abstract

Thermal shape fluctuations of grafted microtubules were studied using high resolution particle tracking of attached fluorescent beads. First mode relaxation times were extracted from the mean square displacement in the transverse coordinate. For microtubules shorter than 10 um, the relaxation times were found to follow an L^2 dependence instead of L^4 as expected from the standard wormlike chain model. This length dependence is shown to result from a complex length dependence of the bending stiffness which can be understood as a result of the molecular architecture of microtubules. For microtubules shorter than 5 um, high drag coefficients indicate contributions from internal friction to the fluctuation dynamics.