NMR Analyses of Carbohydrate–Water and Water–Water Interactions in Water/DMSO Mixed Solvents, Highlighting Various Hydration Behaviors of Monosaccharides Glucose, Galactose and Mannose

Abstract Interaction with water molecules is a potential factor for regulating carbohydrate functions. We analyzed the influences of methyl α-glucoside, methyl α-galactoside and methyl α-mannoside on water in solution through NMR measurements. In order to compare the hydration behaviors according to the geometric characteristics of monosaccharides, proton exchanges between the carbohydrate and water and between water molecules were observed using H2O/D2O and dimethylsulfoxide mixed solvents to employ deuterium-induced isotope shifts. 13C NMR analyses focused on the carbohydrate hydroxy groups revealed that the carbohydrate–water proton exchange in the mannoside solution proceeded slower than in others. Meanwhile, the frequent proton exchange between waters in the mannoside solution was shown by NMR observations of water signals. Our NMR experimental results shed light on the variation of solvation environments of carbohydrates according to their geometric characteristics. Mannose presumably allows for unique orientations of the adjacent water molecules to induce the expansion of water networks efficiently.