Polyelectrolyte Driven Complexation of Sequence Specific Polypeptides

Polyelectrolyte complexes form when oppositely charged polymers are mixed together in aqueous media, resulting in a polymer-rich complex phase coexisting with a polymer-depleted supernatant phase. The complex phase exists as an equilibrium liquid coacervate or a glassy precipitate, depending on the strength of electrostatic interactions. In this study, we examined the effects of polyelectrolyte chain length and sequence, as well as solution pH and ionic strength on complexation behavior and polyelectrolyte microstructure using a variety of spectroscopic and scattering techniques. Initially, we used charged homopolymer polypeptides – (poly)-lysine and (poly)-glutamic acid. This model system allows the chain length, side-chain functionality and chirality to be tuned while keeping the backbone chemistry constant, thus enabling a systematic investigation of polyelectrolyte chain conformation. In addition, we modified the polypeptide sequence to study the effects of charge density and hydrophobicity on polyelectrolyte complexation. Overall, understanding the microstructure and the underlying forces that drive polyelectrolyte complexation will enable design of novel materials for applications ranging from drug delivery to coatings.