| 초록 |
Salt-induced precipitation has been successfully applied for separating process proteins in downstream processing. For efficient design of a protein separation process, good understanding of the phase behavior of proteins in aqueous electrolyte solutions is helpful.In our previous work1, we proposed an equation of state for single protein system based on Chiew’s model for homopolymers to take into account the pre-aggregation effect for protein particles. As pre-aggregated single proteins have similar structures to that of polymers, the chain-connectivity for homopolymers was employed to represent pre-aggregation behaviors in protein systems. In binary protein systems, however, the pre-aggregation is expected to occur between different protein particles as well as the single ones. Therefore, simple chain-connectivity that can be used for homopolymers cannot be adapted in mixtures composed of different proteins. Song et al.2 and Hino et al.3 recently proposed a perturbed hard-sphere-chain (PHSC) equation ofstate for copolymer mixtures based on a modified form of Chiew’s equation of state for athermal mixtures of heteronuclear hard-sphere chains. On the assumption that the pre-aggregated protein mixture has structural similarity to copolymers, the PHSC equation of state developed for copolymer mixtures is considered to be applied to describe the pre-aggregation behaviors in protein mixtures. In this study, we propose a molecular thermodynamic model for the binary protein systems to explain the effect of pre-aggregations occurring between unlike protein particles, which is based on the PHSC equation of state for copolymer mixtures. In the absence of pre-aggregation, we investigate the effect of size disparities and salt concentrations on the osmotic pressure. The influence of protein pre-aggregation for different types of proteins is also discussed.
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