Enzyme kinetics in salt resistant complex coacervate emulsions

Research in protocells has burgeoned in recent decades due to their fundamental importance in the origin of life and their latent technological potential. Complex coacervates formed by liquid-liquid phase separation of charged macromolecules can be simplistic protocellular models with a distinct interface, spontaneous biomolecular sequestration, and chemical conversions within macromolecularly crowded environments. While the bulk material properties of such coacervates are well understood, this knowledge is yet to be applied towards tailoring protocell design. A major limitation was the long-term stabilization of the liquid-liquid interface, which we previously demonstrated using comb-polyelectrolytes (cPEs). In this talk, we demonstrate that this approach is generic and works with distinct polymer characteristics and salt identities, over a wide range of concentrations. We show improved salt resistance of droplets, tunable by cPE concentration and an expansion of the two-phase window. Improvement of coaocervate droplet interfacial stability by cPEs is attributed to both kinetic and thermodynamic effects. In essence, at low cPE concentration, the excess charge by its pressence does not influence the phase behavior significantly and the droplets are kinetically stabilized. At higher cPE concentrations, both kinetic and thermodynamic effects stabilize the coacervate droplets against salt.