Liquid-liquid phase separation plays an important role in cellular organization, and it is an emerging alternative in compartment-first hypotheses for the origin of life. Control over phase separation by enzymatic reactions is essential in order to use droplets as organelle mimics or protocells. To elucidate the physicochemical principles that govern the nucleation, growth and coarsening of biomimetic droplets, we use ATP-based complex coacervate droplets that we control by a kinase reaction. We track the coacervates by microscopy and follow their active growth at a single-droplet level. We quantify the partitioning of all components in our system by HPLC and fluorescence labelling to support our results with a kinetic comparison. We show that droplet size increases as a result of the chemical reaction, an active behavior that is a plausible mechanism for protocellular growth. Moreover, growth rate can be averaged over the entire droplet population, and is significantly affected by environmental conditions and droplet composition. We also find that Ostwald ripening is suppressed in complex coacervates, and therefore these compartments, although membraneless, are more stable than it is usually speculated in the literature. Our findings show that the behavior of active droplets, obtained through coupling phase separation to enzymatic reactions, can be quantified and explained in terms of chemical principles.
Active coacervate droplets: protocells that grow and survive
I obtained my BSc (2012) and MSc (2015) Chemistry degrees at the University of São Paulo. I came to the Netherlands in 2017 for my PhD to investigate how chemical reactions can control coacervate droplets and vice-versa, as a small step in understanding cells and the chemical origin of life
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