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J Chromatogr A. 2015 Dec 18;1425:51-61. doi: 10.1016/j.chroma.2015.11.019. Epub 2015 Nov 10.

Effect of sodium chloride on solute-solvent interactions in aqueous polyethylene glycol-sodium sulfate two-phase systems.

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CEB-Centre of Biological Engineering, University of Minho, 4710-057 Braga, Portugal.
Analiza, Inc., 3615 Superior Ave., Cleveland, OH 44114, USA.
Laboratory of Separation and Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering of the University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA.
Analiza, Inc., 3615 Superior Ave., Cleveland, OH 44114, USA. Electronic address:


Partition behavior of eight small organic compounds and six proteins was examined in poly(ethylene glycol)-8000-sodium sulfate aqueous two-phase systems containing 0.215M NaCl and 0.5M osmolyte (sorbitol, sucrose, TMAO) and poly(ethylene glycol)-10000-sodium sulfate-0.215M NaCl system, all in 0.01M sodium phosphate buffer, pH 6.8. The differences between the solvent properties of the coexisting phases (solvent dipolarity/polarizability, hydrogen bond donor acidity, and hydrogen bond acceptor basicity) were characterized with solvatochromic dyes using the solvatochromic comparison method. Differences between the electrostatic properties of the phases were determined by analysis of partitioning of sodium salts of dinitrophenylated (DNP-) amino acids with aliphatic alkyl side-chain. The partition coefficients of all compounds examined (including proteins) were described in terms of solute-solvent interactions. The results obtained in the study show that solute-solvent interactions of nonionic organic compounds and proteins in polyethylene glycol-sodium sulfate aqueous two-phase system change in the presence of NaCl additive.


Aqueous two-phase system; Partitioning; Proteins; Solute–water interactions; Solvatochromic comparison method; Solvent properties

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