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Behavior of Active Polymer Knots.

Zhiyu Zhang1, Longfei Li2, Yongjian Zhu1

  • 1Department of Physics, City University of Hong Kong, Hong Kong 999077, China.

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Summary
This summary is machine-generated.

Active polymer knots exhibit unique behaviors like tightening and breathing due to internal forces. These findings offer insights into biopolymers such as DNA.

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Area of Science:

  • Polymer Physics
  • Biophysics
  • Soft Matter Physics

Background:

  • Active polymers are crucial in biological systems.
  • Polymer knotting influences chain dynamics and properties.
  • Understanding active polymer knots is key to biopolymer function.

Purpose of the Study:

  • To investigate the behavior of active polymer knots.
  • To explore the effects of activity strength on knot properties.
  • To elucidate the dynamic differences between active and non-active polymer knots.

Main Methods:

  • Brownian dynamics simulations were employed.
  • An approximate theory was developed to quantify knot size dependence on Péclet number (Pe).
  • Simulations analyzed knot size, conformation, and dynamics.

Main Results:

  • Active force significantly tightens knots via an activity-induced stretching effect, with varying magnitude inside and outside the knot core.
  • Active polymer knots display dynamic "knot breathing"—switching between loose and tight states—unlike non-active knots.
  • Activity-induced chain shrinkage was observed in short chains, enhanced by knotting.
  • In long chains, activity-induced shrinkage is counteracted by segment reallocation, leading to overall conformation enlargement.

Conclusions:

  • Active forces introduce novel phenomena in polymer knots, including enhanced tightening and dynamic breathing.
  • Knotting influences the response of active polymers to internal forces, affecting shrinkage and stretching.
  • These findings have potential implications for understanding the behavior of biopolymers like DNA.