Dresden 2020 – scientific programme

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BP: Fachverband Biologische Physik

BP 8: Poster I

BP 8.4: Poster

Monday, March 16, 2020, 17:30–19:30, P2/1OG

Size control of Active Droplets with Non-Equilibrium Chemical Reactions — •Jan Kirschbaum and David Zwicker — Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany

Liquid droplets forming by phase separation play an important role in the spatiotemporal organization of material inside cells. However, in contrast to passive phase separation, e.g. oil-water emulsions, the interaction of cellular droplets with their inherently non-equilibrium environment is not well understood. Here, we investigate how ATP-driven chemical reactions, which switch a protein between a phase separating and a soluble form, influence the properties of droplets. Similar systems were already investigated using mass-action kinetics, but such descriptions are not thermodynamically consistent and are thus difficult to compare to experiments.

Here, we employ linear non-equilibrium thermodynamics to model the phase separation and the non-equilibrium reactions. We identify that droplet size and stability can be controlled when one reaction is driven and the enzymes controlling the rates are distributed heterogeneously. In this case, a non-equilibrium steady state with well-defined droplet radius can be reached, characterized by constant diffusive and reactive fluxes inside the system. Using the model, we determine the energy consumption and entropy production rate necessary to maintain droplets of certain sizes. For the biological example, we thus propose that enriching enzymes in droplets is one way to control their size by chemical reactions.