(692c) Theory of Sequence-Controlled Complex Coacervation

Proteins are heteropolymers consisting of 20 types of monomer units, which differ in amino acid residues. The primary structure of proteins, i.e., linear sequence of monomers, defines their secondary, tertiary and quaternary structures, and therefore their properties and biological activity. In the present work, we study a solution of oppositely charged polyelectrolytes, where the primary structure of polyions containing 2 types of monomers, charged and neutral, also plays a key role.¹ In the framework of the random phase approximation (RPA) we show that the sequence of units in partially charged polyelectrolytes decisively affects their complex coacervation, i.e., the phase behavior of the solution. A higher degree of blockiness of charged monomers favors formation of denser coacervates and strongly enhances their salt resistance. Binodals of the solutions of polyelectrolytes with different primary structures are plotted, and the region of two-phase solution state is shown to become much wider with increasing charge blockiness. This is due to improved cooperativity of Coulomb interactions between opposite charges within the coacervate. Results of analytical theory are compared with the simulations data.

[1] L.-W. Chang, T. K. Lytle, M. Radhakrishna, J. J. Madinya, J. Velez J., C. E. Sing, S. L. Perry. Sequence and entropy-based control of complex coacervates. Nature Commun. 2017, 8, 1273.