Regensburg 2025 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 46: Statistical Physics of Biological Systems II (joint session DY/BP)

DY 46.1: Hauptvortrag

Freitag, 21. März 2025, 11:30–12:00, H43

Equilibrium and non-equilibrium dynamics of biological systems with memory — •Roland Netz — Freie Universität Berlin, Fachbereich Physik, Berlin

Biological systems are many-body systems. Thus, their dynamics, when described in terms of a low-dimensional reaction coordinate, is governed by the generalized Langevin equation (GLE), an integro-differential equation of motion which contains friction memory [1]. Two examples will be discussed:

Protein-folding kinetics is standardly described as Markovian (i.e., memoryless) diffusion in a one-dimensional free-energy landscape. By analysis of molecular-dynamics simulation trajectories of fast-folding proteins the friction is demonstrated to exhibit significant memory with a decay time of the same order as the folding and unfolding times [2,3,4]. Memory friction leads to anomalous and drastically modified protein kinetics: the folding and unfolding times are not dominated by free-energy barriers but rather by non-Markovian friction.

Active motion of organisms obviously is far from equilibrium. The parameters of an appropriate non-equilibrium GLE are extracted from trajectories. It is demonstrated that the motion of single-cellular algae is characterized by pronounced memory friction, which allows to classify and sort individual cells.

[1] Memory and Friction: From the Nanoscale to the Macroscale, BA Dalton, A Klimek, H Kiefer, F N Brünig, H Colinet, L Tepper, A Abbasi, RR Netz, https://arxiv.org/pdf/2410.22588

Keywords: protein folding; active motion; memory effects; non-Markovian effects; generalized Langevin equation