Charge stabilization and dynamics in polyelectrolyte phase separation

The phase separation of biological polyelectrolytes underlies the formation of biomolecular condensates that perform diverse cellular functions. Here, we investigate the role of polymer charge in the phase separation dynamics and stabilization of polyelectrolyte domains in a solution containing dissolved salt ions. Employing a continuum theory, we study the dynamics of patterns that emerge during spinodal decomposition. We present relationships between key polymeric and solution parameters that determine the degree of charge stabilization, and define a region of finite-wavelength instability. Solving the time-dependent equations, we find that the polymer net charge determines the dynamics of phase separation, and thus a critical charge fraction may classify a polymer's modes of instability. By comparing the theory predictions to databases of drivers of biological phase separation, the mechanism of charge stabilization is suggested to be relevant for a variety of proteins.