9510420 Lenhoff This proposal is on research to continue to develop a quantitative thermodynamic basis for the analysis and design of protein separations, comparable to that which is routinely applied to conventional separations in the chemical process industries. This will involve research on: (1) molecular theories to predict key thermodynamic properties of proteins in solution, based on protein structure, when it is known, and on key experimental biophysical characteristics, when the structure is not known, and (2) use of the descriptions of phase behavior and physical properties to develop rational, thermodynamically- based approaches to predict separation performance for important processes, including precipitation and two-phase aqueous extraction. ***