Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session PP05: V: Optical, Electronic, Ionic, and Piezoelectric Properties of Polymers and Composites
9:00 AM–11:00 AM,
Tuesday, March 21, 2023
Room: Virtual Room 5
Sponsoring
Unit:
DPOLY
Chair: Bryan Boudouris, Purdue University
Abstract: PP05.00010 : Lifetime of Metastable Knots in Polyampholyte Chains*
10:48 AM–11:00 AM
Presenter:
masoumeh ozmaeian
(West Texas A&M)
Authors:
masoumeh ozmaeian
(West Texas A&M)
Dmitrii E Makarov
(University of Texas at Asutin)
Knots in proteins and DNA are known to have significant effect on their equilibrium and dynamic properties as well as on their function. While knot dynamics and thermodynamics in electrically neutral and uniformly charged polymer chains are relatively well understood, proteins are generally polyampholytes, with varied charge distributions along their backbones. Here we use simulations of knotted polymer chains to show that variation in the charge distribution of a polyampholyte chain with zero net charge leads to large variation in the resulting knot dynamics, with some charge distributions resulting in long-lived metastable knots that escape the (open-ended) chain on a timescale that is much longer than that for knots in electrically neutral chains. The knot dynamics in such systems can be described, quantitatively, using a simple one-dimensional model where the knot undergoes biased Brownian motion along a “reaction coordinate”, equal to the knot size, in the presence of a potential of mean force. In this picture, long-lived knots result from charge sequences that create large electrostatic barriers to knot escape. This model allows us to predict knot lifetimes even when those times are not directly accessible by simulations.
*This work was supported by the Robert A. Welch Foundation (Grant No. F-1514) and the National Science Foundation (Grant No. CHE 1566001).
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