1H NMR Elucidation of Observed Stable Sugar-NaCl-water Complexes in Aqueous Solution**

Abstract

The solvation of sugars in aqueous media matters in the understanding of biological systems and carbohydrate transformations. The presence of NaCl is known to perturb hydrogen bonding of sugar hydrates, however, direct evidence to elucidate mechanism at atom level is very rare even though the “NaCl Effect” was well known in biomass transformations for chemicals/biofuels. Here we report experimental evidences of a clear staircase-like correlation between induced ¹H NMR changes of D-glucose/fructose with concentration of NaCl aqueous solution at room temperature; and two stable bonding status was observed in the system. HDO in sugar/NaCl aqueous solution as a “dynamic” reference is a key to enable decoupling the global salt effect in this ¹H NMR investigation of NaCl-saccharide interaction. Via a further half-quantitative study, three structures of stable sugar-NaCl-water complexes were mapped for the first time in tackling the NaCl-monosaccharide interaction at atomic level in an aqueous solution. Based on the maximum of induced ¹H NMR shifts, an ideal NaCl usage was proposed.