(475c) Selectivity of Complex Coacervation in Engineered Protein Mixtures

Oppositely charged polyelectrolytes can undergo complex coacervation, an associative liquid-liquid phase separation. This phase transition is driven by electrostatic attraction between the polymers and entropic gains from counterion release. The resulting polymer rich phase, termed the coacervate phase, has a range of potential applications from protein stabilization to underwater adhesives and biomimetic compartments. Here we investigate the utility of complex coacervation as a protein purification technique as the phase separation can be highly selective, while being high throughput and low-cost. Previous work has demonstrated that a protein of interest can be enriched from a relatively simple mixture of two proteins. In this work, we quantitatively assess protein recovery and purity from a more complex mixture of at least five proteins. Using spectrally separated engineered proteins, we have evaluated the phase separation of individual proteins as well as mixtures of these proteins with a model polycation. We have demonstrated that by tuning the salt concentration and pH, proteins of varying net charge can be selectively enriched and recovered from the complex mixture. Further, we have shown the ability to translate these findings from this well-defined mixture to the more complex milieu of the E. coli cell lysate.