Translocation and phase separation kinetics in polyelectrolyte solutions

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TECHNICAL SUMMARY:The movement of charged macromolecules in crowded aqueous solutions and the thermodynamic stability of such multi-component macromolecular systems are of central importance in various forms of life. The thermodynamic and dynamic behaviors of polyelectrolyte solutions in water exhibit extremely complex phenomenology and pose many challenges for a fundamental understanding. The proposal is to perform electrophysiology and light scattering experiments pertinent to a fundamental understanding of (a) translocation of single polyelectrolyte molecules through protein and solid-state nanopores, (b) kinetics of phase separation in polyelectrolyte solutions, and (c) dynamics of elastic modes accompanying phase transitions in polyelectrolyte gels. Specifically, the proposed research addresses (a) the dynamics of polyelectrolyte chains with specified architecture (uniformly charged linear molecules, diblock copolymers of charged and uncharged polymers, branched polyelectrolytes, and polyelectrolyte complexes) through nanopores (hemolysin protein pore with fixed pore diameter and silicon nitride pores with controllable variations in diameter), (b) phase separation kinetics of sodium poly(styrene sulfonate) in water containing known amounts of barium chloride, and (c) dynamical fluctuations of polyacrylamide-polyacrylic acid copolymer gels accompanying their first order volume phase transitions. The proposed research will establish the validity and generality of a few newly discovered phenomena related to translocation of synthetic polyelectrolyte molecules through protein pores, phase separation mechanism in electrically charged polymeric solutions, and pretransitional slowing down of elastic modes in gels.NON-TECHNICAL SUMMARY:The proposed research will have impact in separation science, characterization methods for charged macromolecules in aqueous media, and medical research, and a number of key industries including food, cosmetics, personal care products, pharmaceuticals, and the human genome sequencing project. Polyelectrolytes are among the most important but least understood materials. This research will use a number of experimental methods together with theory and simulations in an attempt to understand how polyelectrolyte molecules are able to pass through pores in protein assemblies and other biological systems. Training of graduate students in this highly interdisciplinary research area is the primary educational component of the proposed activity.