Analyzing the effects of protecting osmolytes on solute–water interactions by solvatochromic comparison method: I. Small organic compounds

Abstract

Solvent properties of water (dipolarity/polarizability, hydrogen bond donor (HBD) acidity, and hydrogen bond acceptor (HBA) basicity) in aqueous solutions of osmolytes (sorbitol, sucrose, trehalose, and trimethylamine N-oxide (TMAO)) were studied at different osmolyte concentrations using a solvatochromic comparison method. The solvent properties of aqueous media in the coexisting phases of aqueous dextran–PEG–sodium/potassium phosphate buffer (0.01 M K/NaPB, pH 7.4) two-phase system (ATPS) containing 0.5 M osmolyte additive (sorbitol, sucrose, trehalose, TMAO) and osmolyte-free ATPS were characterized. Partitioning of 30 low molecular weight polar organic compounds was examined in aqueous dextran–PEG–0.01 M K/NaPB ATPS containing 0.5 M sorbitol. The solute-specific coefficients for the compounds examined were determined from the data obtained here and those reported previously. The results obtained demonstrate that the osmolytes examined affect the partition behavior of organic compounds in ATPS by influencing solvent properties of the media and not by direct association with the compounds.