Towards understanding the physicochemical principle of molecular sequestration by coacervates protocells

Coacervates are micron-sized liquid droplets, formed by liquid-liquid phase separation directed by attractive and segregative forces, that have attracted considerable interest as protocells. These droplets are used as in-vitro models for membraneless organelles in cells, which store and protect cellular material from the environment. Their ability to encapsulate reactions, preserve the products against environmental fluctuations, and possibly allow for the emergence of more complex molecular structures all suggest that they may have played a role in the formation of cells at the origins of life. A key role in protocell models, as well as in modern-day biological processes, is played by the interactions of coacervates with the surrounding environment and their ability to exchange molecules with the dilute phase. Given the complexity of interaction networks arising from multi-component systems and the large number of molecules involved, predicting host-client partitioning and understanding the effect on coacervates of sequestered molecules is still a significant scientific challenge. In this study, we investigated the physicochemical principle underlying coacervate assembly and sequestration of clients from the environment. We applied a combined experimental and numerical approach to unravel their behaviors, analyzed the influence of ions on two coacervate systems, constructed their phase diagrams, and took the initial steps in the study of the partition properties of small client molecules in coacervates.