Research Summary: The objective of this research is to develop a more fundamental understanding of the thermodynamic and mechanical properties of concentrated protein solutions, including protein gels, under conditions where both inter- and intra-molecular interactions are important. Experimental studies, employing bovine serum albumin as a model system, will involve both osmotic pressure measurements and tracer solute partitioning during osmotic equilibrium. In combination, these data can be used to evaluate solution non-idealities and the compressive pressure, a parameter used in the thermodynamic model to characterize the contribution of both inter- and intra-molecular interactions. Theoretical analyses of solution non-idealities will involve application of polymer lattice models, for example, Flory-Huggins theory, to the concentrated protein solutions. Inter-molecular attractions and repulsions will be modelled using McMillan-Mayer solution theory. Potential Impact: The results from the current study, as well as those from future investigations, will have applications in the analysis of a variety of protein separation processes in which inter- and intra-molecular interactions are thought to be important, e.g., protein crystallization and precipitation. The thermodynamic data and models will also provide insight into the use of liquid-liquid extraction for protein separations. The results from this study can also be used to analyze selective protein filtration, the use of membrane ultrafiltration to separate proteins of differing molecular weight on the basis of size.
