Regensburg 2025 – scientific programme

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BP: Fachverband Biologische Physik

BP 20: Statistical Physics of Biological Systems I (joint session BP/DY)

BP 20.2: Talk

Wednesday, March 19, 2025, 15:15–15:30, H44

Phase separation in membranes and compartments with binding reactions — •Riccardo Rossetto, Gerrit Wellecke, and David Zwicker — Max Planck Institute for Dynamics and Self-Organization

Biological cells exhibit a hierarchical spatial organization, where various compartments and membranes harbor condensates that form by phase separation. Cells can control the emergence of these condensates by affecting the physical interactions of the involved biomolecules, thus also tuning the binding affinity to the compartments. We describe this situation with a thermodynamically-consistent kinetic model considering passive and active binding reactions to elucidate their role in controlling the occurrence and timescales of phase separation in compartments. On the one hand, binding reactions can lead to the emergence of new equilibrium phenomena, such as re-entrant phase transitions and multistability. On the other hand, they can also affect the kinetics of phase separation. As a particular example, we consider protein droplets in cellular membranes when proteins can also unbind to the cellular bulk. For fast bulk diffusion, this leads to effective nonlocal transport, which fundamentally affects droplet dynamics. For instance, the seminal Lifshitz-Slyozov coarsening can be abolished. Furthermore, active binding reactions can both accelerate or fully suppress coarsening, leading to protein patterns on the membrane. The general conclusions from our model unveil fundamental mechanisms of phase separation in membranes and compartments, and will help us explain more biological observations in the future.

Keywords: Phase separation; Compartments; Coarsening; Nonlocal transport; Pattern formation