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Non-equilibrium effects of molecular motors on polymers

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Abstract

We present a generic coarse-grained model to describe molecular motors acting on polymer substrates, mimicking, for example, RNA polymerase on DNA or kinesin on microtubules. The polymer is modeled as a connected chain of beads; motors are represented as freely diffusing beads which, upon encountering the substrate, bind to it through a short-ranged attractive potential. When bound, motors and polymer beads experience an equal and opposite active force, directed tangential to the polymer; this leads to motion of the motors along the polymer contour. The inclusion of explicit motors differentiates our model from other recent active polymer models. We study, by means of Langevin dynamics simulations, the effect of the motor activity on both the conformational and dynamical properties of the substrate. We find that activity leads, in addition to the expected enhancement of polymer diffusion, to an effective reduction of its persistence length. We discover that this effective “softening” is a consequence of the emergence of double-folded branches, or hairpins, and that it can be tuned by changing the number of motors or the force they generate. Finally, we investigate the effect of the motors on the probability of knot formation. Counter-intuitively our simulations reveal that, even though at equilibrium a more flexible substrate would show an increased knotting probability, motor activity leads to a marked decrease in the occurrence of knotted conformations with respect to equilibrium.

Graphical abstract: Non-equilibrium effects of molecular motors on polymers

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Publication details

The article was received on 07 Feb 2019, accepted on 25 Jun 2019 and first published on 11 Jul 2019


Article type: Paper
DOI: 10.1039/C9SM00273A
Soft Matter, 2019, Advance Article
  • Open access: Creative Commons BY-NC license
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    Non-equilibrium effects of molecular motors on polymers

    M. Foglino, E. Locatelli, C. A. Brackley, D. Michieletto, C. N. Likos and D. Marenduzzo, Soft Matter, 2019, Advance Article , DOI: 10.1039/C9SM00273A

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