Measuring cohesion between macromolecular filaments, one pair at a time: Depletion-induced microtubule bundling

Abstract

In presence of non-adsorbing polymers, colloidal particles experience ubiquitous attractive interactions induced by depletion forces. Here, we measure the depletion interaction between a pair of microtubule filaments using a method that combines single filament imaging with optical trapping. By quantifying the dependence of filament cohesion on both polymer concentration and solution ionic strength, we demonstrate that the minimal model of depletion, based on the Asakura-Oosawa theory, fails to quantitatively describe the experimental data. By measuring the cohesion strength in two- and three- filament bundles we verify pairwise additivity of depletion interactions for the specific experimental conditions. The described experimental technique can be used to measure pairwise interactions between various biological or synthetic filaments and complements information extracted from bulk osmotic stress experiments.

References in corpus (5)

• Spontaneous motion in hierarchically assembled active matter
• Isotropic-nematic phase transition in suspensions of filamentous virus and the neutral polymer Dextran
• Polymer induced depletion potentials in polymer-colloid mixtures
• Solid friction between soft filaments
• The pair potential of colloidal stars

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