Compositional Analysis of Crowded Polyelectrolyte Complex Coacervates

In this poster, we discuss the influence of macromolecular crowders on the phase behavior of polyelectrolyte complex (PEC) coacervates. PEC coacervates form in aqueous solutions upon complexation of oppositely charged polyelectrolytes, resulting in a two-phase system of a polymer-dense complex and polymer-lean supernatant phases. The composition and volume of the two phases are heavily influenced by the presence of crowders, molecules that do not participate in the electrostatic interactions driving complexation but rather reduce the free volume available in the system. These polyelectrolyte-crowder systems are of high interest as they have been shown to model behaviors of membraneless organelles, though no systematic studies have been performed to fully capture the effect of crowders on the thermodynamics of complexation. Here, we employ a neutral crowder of increasing length in a coacervating system to show that the infiltration of the crowder molecules into the complex phase and the relative volumes of each phase are both highly dependent on crowder length and concentration. Our findings provide insight into the substantial effect of crowders on the composition of PEC coacervates and further our understanding of similarly crowded biological phase-separated systems.