Phase Equilibrium of Aqueous Two-Phase Systems
Date Issued
2008
Date
2008
Author(s)
Yang, Jhih-Jie
Abstract
Aqueous two-phase systems are prepared by combining two water-soluble polymers or a salt in water, above a critical concentration. These systems separate into two immiscible liquid phases, one of them enriched in one polymer and the other enriched in the other polymer or salt. Aqueous two-phase extraction method has been recognized as a nondenaturing and nondegrading technique of a number of biological entities such as proteins, enzymes, viruses, cells, and cell organelles. In this work, dissipative particle dynamics (DPD) is employed to investigate aqueous two-phase systems (ATPSs). The study can be divided into two parts. The first is the study of the effects the compatibility of two polymers, concentrations of two polymers and molecule length of two polymers on the formation of aqueous two-phase systems. The second is the extraction efficiency. We consider partition coefficient K as an index of the extraction efficiency, and vary the compatibility of two polymers, concentrations of two polymers, molecule length of two polymers and molecule length of the extractor in search of the best extraction efficiency. According to the simulation results, we observe that aqueous two-phase systems consist of three parts : polymer 1 – rich region, polymer 2 – rich region and boundary. As the incompatibility of two polymers, concentrations of two polymers and molecule length of two polymers increases, degree of phase separation becomes more obvious. Eventually, only negligible amounts of polymer 1 are found in the polymer 2 – rich phase and vice versa. In the boundary region, water forms a buffer zone to alleviate the repulsive interactions between polymers 1 and 2. Therefore, as the repulsion increases, the concentration of water increases. Simulation results also indicate that the partition coefficient (thus the extraction efficiency) is significantly affected by the degree of phase separation and therefore all the factors that have an effect on phase separation influence the extraction efficiency.
Subjects
Aqueous Two-Phase Systems
Type
thesis
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