Polyelectrolyte-Colloid Interactions

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9619722 Dubin The interaction of polyelectrolytes with colloidal particles and surfaces is central to a many industrial processes and biological phenomena, such as dispersion stabilization and flocculation, and the binding of. proteins to DNA. Since these interactions are predominantly coulombic,the PI will study systems in which key electrostatic quantities -- colloid surface charge density, polymer linear charge density, and ionic strength,--can be systematically varied. The polyelectrolytes will be both cationic, such as poly(dimethyldiallylammonium chloride), and anionic, such as poly(acrylamido-2-methylpropanesulfonate) and copolymers thereof. The colloidal particles studied will be micelles, vesicles, proteins and dendrimers. Some of these systems have individual significance, e.g. polyelectrolyte-protein complexes for protein separations, polyelectrolyte-micelle complexes for removal of trace organics, and polyelectrolyte vesicle complexes for drug delivery. One of the goals will be to evaluate two very distinct theoretical treatments. The first predicts second-order phase transitions for polyelectrolyte adsorption on oppositely charged surfaces (large particles. The second describes the binding of charged ligands (small particles) to polyions within the context of counterion condensation theory. In addition, a number of questlons related to specific experimental systems will be addressed: (a) Do mlcelies restructure upon binding to polyions? (b) Can the "spacer effect" of nonionic co- surfactants be quantitatively explained? (c) What is the state of proteins in complexes and coacervates, in terms of tertiary structure, rotational freedom, and enzyme activity? (d) What is the microstructure of protein-polyelectrolyte and micelle-polyelectrolyte coacervates? and (e) How does polyelectrolyte adsorption affect liposome permeability? %%%% This project is in the area of colloidal particles, surfaces, and polyelectrolytes, whose interactions have importan t implications to a number of biological and industrial processes ***