title: Predicting the activity coefficients of free-solvent for concentrated globular protein solutions using independently determined physical parameters.
abstract: The activity coefficient is largely considered an empirical parameter that was traditionally introduced to correct the non-ideality observed in thermodynamic systems such as osmotic pressure. Here, the activity coefficient of free-solvent is related to physically realistic parameters and a mathematical expression is developed to directly predict the activity coefficients of free-solvent, for aqueous protein solutions up to near-saturation concentrations. The model is based on the free-solvent model, which has previously been shown to provide excellent prediction of the osmotic pressure of concentrated and crowded globular proteins in aqueous solutions up to near-saturation concentrations. Thus, this model uses only the independently determined, physically realizable quantities: mole fraction, solvent accessible surface area, and ion binding, in its prediction. Predictions are presented for the activity coefficients of free-solvent for near-saturated protein solutions containing either bovine serum albumin or hemoglobin. As a verification step, the predictability of the model for the activity coefficient of sucrose solutions was evaluated. The predicted activity coefficients of free-solvent are compared to the calculated activity coefficients of free-solvent based on osmotic pressure data. It is observed that the predicted activity coefficients are increasingly dependent on the solute-solvent parameters as the protein concentration increases to near-saturation concentrations.
authors: B2K Group (Biotransport & Bioreaction Kinetics Group), Center for Bioengineering Research, Department of Bioengineering, University of California Riverside, Riverside, California, United States of America.
authors: Devin W
authors: DW
authors: McBride
authors: Victor G J
authors: VG
authors: Rodgers
mesh_terms: D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D006454:Hemoglobins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D012756:Sheep; D012996:Solutions; D012997:Solvents / Q000737:chemistry*; D013395:Sucrose / Q000737:chemistry
chemical_list: D006454:Hemoglobins; D012996:Solutions; D012997:Solvents; D012710:Serum Albumin, Bovine; D013395:Sucrose