Controlling membrane-less organelles via chemical reactions

Liquid-like droplets, formed by phase separation, play a crucial role in the spatiotemporal organization of membrane-less organelles inside cells. While passive phase separation is well understood, the interaction with the non-equilibrium environment inside biological cells is not. We investigate how fuel-driven chemical reactions influence the properties of those organelles when the droplet material can switch between a phase separating and a soluble form. We model this non-equilibrium system based on the chemical potential as a driving force for both the reaction and diffusion. First, we show how driven chemical reactions can control the total amount of phase separating material. We then, motivated by experiments, introduce heterogeneously distributed enzymes, which lead to spatial varying reaction rates. In this case, the system reaches a non-equilibrium steady state in which the diffusive and reactive fluxes are constant. The balance of these fluxes can lead to a collective state where multiple droplets of the same size coexist. The model also allows us to characterize the energy consumption and entropy production rate to quantify the cost of maintaining a fixed droplet size.