Understanding folded protein and polyelectrolyte coacervation.

Rituparna Samanta, Venkat Ganesan

University of South Florida

A mixture of folded proteins and polyelectrolytes are widely used in applications such as food systems, biosensors, protein purification, and drug delivery. Proteins and polymers form a liquid-liquid phase separation called coarcervation.  Experiments have demonstrated that the structures and phase behavior of protein-polyelectrolyte mixture can depend on a variety of factors, including the physical and chemical characteristics of proteins, polyelectrolytes, properties of solution, and temperature. Despite extensive experimental studies, there is a lack of understanding of the underlying fundamental physics of the protein-polyelectrolyte mixtures and the ability to predict the impact of the protein properties on the structure of these mixtures. Motivated by this gap, we have built a single chain in mean-field-based coarse-grained multibody simulation framework to study the phase behavior of protein and polyelectrolyte complexes. I will discuss the influence of features such as the dielectric difference between the protein and the solvent, charge distribution of proteins, solution pH, and their effect on the phase behavior of the complex. Our results demonstrate that the pattern of charge heterogeneities can exert a significant influence on the resulting characteristics of the aggregates, in some cases leading to a transformation from polymer-bridged complexes to direct protein aggregates.  We found the effect of bridging by polyelectrolytes leading to protein aggregation more pronounced when we included the effect of dissociation. Our versatile coarse-grained field-based model helps access longer time and length scale phase separation, study the independent effect of component features, and finally reverse engineer the components for desired purposes.

It would be helpful if I have my presentation before Saturday. I may not be able to join on Saturday.