SEMINAR 2024

Multiscale Behavior of Biopolymer Structure and Dynamics

SpeakerAshesh Ghosh
Department of Chemistry, University of California Berkeley, Berkeley CA
Department of Chemical Engineering, University of California Berkeley, Berkeley CA
Division of Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley CA
Date/TimeMonday, 7 Oct, 11AM
LocationConference room: S11-02-07
HostProf Yan Jie

Abstract

A coherent understanding of a biophysical system requires merging orders of magnitude length and timescale phenomena in a coordinated fashion. The talk will detail over the behavior of biopolymers spanning the collective response to single polymer structural and mechanical properties.

For the first part, I will discuss how protein filaments on the endosomal membrane can leverage a rigid-to-flexible transformation to elicit a large-scale change in membrane flexibility to enable membrane fusion. Specifically, a polymer field-theoretic model encapsulating molecular alignment arising from nematic interactions between polymers will be discussed. The collective elasticity and alignment interactions of the filament brush layer results in more than 20-fold increase of the effective membrane rigidity over bare membrane elasticity. Thus, the collective state of the polymers induce membrane rigidification (fluidization), in turn impeding (facilitating) vesicle fusion.

Interplay of bipolymers structure and dynamics at various length and timescales drive a myriad of crucial life processes. The left image shows EEA1 protein driven modulation of membrane fluctuations while at much smaller scale the polymers are coil-coiled helix much like dsDNA, that can be modeled by a twist-bend coupled helical wormlike chain model.

For the second part, I will focus on the structural and mechanical properties of a single biopolymer. Biopolymers are often modeled using the famous wormlike chain model that ascribes bending energy of deformation along the polymer backbone length. However, recent experiment demonstrates the importance of twist and twist-bend coupling in the context of dsDNA and other biopolymers. I will present an exact solution for the Green’s function for the general case of a helical wormlike chain with twist-bend coupling, and demonstrate the applicability of the exact solution for evaluating general structural and mechanical properties of the polymer. The exact nature of the solution provides a framework to evaluate the role of twist-bend coupling on polymer properties and motivates the reinterpretation of existing bio-polymer experimental data.

Broadly, the concepts and ideas presented in the talk paves the way to understand the multiscale structural and mechanical behavior of free and bound biopolymers.

Biography

Ashesh is a postdoctoral scholar at the University of California Berkeley working at the interface of non-equilibrium statistical mechanics, biophysics, continnum mechanics and molecular simulations. He did his PhD from University of Illinois at Urbana-Champaign working on glassy dynamics of colloids and polymers. His interest in biological systems led him to his first postdoc at Stanford University where he focused on biopolymer structure and dynamics, coarse-grained models and membrane mechanics. In his current role he continues to focus on biophysical systems that are driven far from equilibrium. Broadly, Ashesh intends to apply physics based approaches to solve problems at the intersection of biophysics, chemical physics and biology.