Liquid spherical shells are a non-equilibrium steady state of active droplets

Liquid-liquid phase separation yields spherical droplets that eventually coarsen to one large, stable droplet governed by the principle of minimal free energy. In chemically fueled phase separation, the formation of phase-separating molecules is coupled to a fuel-driven, non-equilibrium reaction cycle. It thus yields dissipative structures sustained by a continuous fuel conversion. Such dissipative structures are ubiquitous in biology but are poorly understood as they are governed by non-equilibrium thermodynamics. Here, we bridge the gap between passive, close-to-equilibrium, and active, dissipative structures with chemically fueled phase separation. We observe that spherical, active droplets can undergo a morphological transition into a liquid, spherical shell. We demonstrate that the mechanism is related to gradients of short-lived droplet material. We characterize how far out of equilibrium the spherical shell state is and the chemical power necessary to sustain it. Our work suggests alternative avenues for assembling complex stable morphologies, which might already be exploited to form membraneless organelles by cells

Front Cover: Toward Customized Tetrahydropyran Derivatives through Regioselective α-Lithiation and Functionalization of 2-Phenyltetrahydropyran (Eur. J. Org. Chem. 19/2016)

Front Cover: Toward Customized Tetrahydropyran Derivatives through Regioselective α-Lithiation and Functionalization of 2-Phenyltetrahydropyra

Active Coacervate Droplets as a Model for Membraneless Organelles and a Platform Towards Synthetic Life

Membraneless organelles like stress granules are active liquid-liquid phase-separated droplets that are involved in many intracellular processes. Their active and dynamic behavior is often regulated by ATP-dependent reactions. However, how exactly membraneless organelles control their dynamic composition remains poorly understood. Herein, we present a model for membraneless organelles based on RNA-containing active coacervate droplets regulated by a fuel-driven reaction cycle. These droplets emerge when fuel is present, but decay without. Moreover, we find these droplets can transiently up-concentrate functional RNA, and that this up-take is accelerated by the chemical reaction cycle. Finally, we show that in their pathway towards decay, these droplets self-divide asymmetrically. Self-division combined with emergence, decay, rapid exchange of building blocks, and functionality are all hallmarks of life, and we believe that our work could be a stepping stone towards its synthesis