Protein Salt Solution Osmotic Pressure

As a important macromolecule, increasing researches on protein have being made recently. For efficient design of a protein separation process, good understanding of the non-ideal ties and phase behavior in aqueous electrolyte solutions is helpful by finding out the thermodynamic mechanism of protein-salt solution. Many theories have been established based on various models. This paper represents the classical DLVO theory by using three Yukawa potentials to describe the attractive dispersion interaction, the double-layer repulsive charge-charge interaction and the newly defined repulsive dispersion interaction between molecules respectively, and combines the first order perturbation theory with Ross variation theory to propose a new equation of state (EOS). The equation of state is applied to study the osmotic pressure for Aqueous Bovine Serum (BSA)-NaCl, lysozyme –(NH4)2SO4 and α-chymotrypsin-K2SO4 solutions with various values of pH and concentration. The results show that precision of new theory with is superior to the theory recently developed by Lin-Yang Zheng et al with only one independent parameter, and as shown in this work, the new theory ,which has one more adjustable parameter, is more reasonable and more accurate than the previous theories in correlation and predictions. By analyzing and contrasting the experimental dates and theoretical values, the limitations of our model are discussed and the suggestion for further improvement is given.