Hydration studies of carbohydrates .4. NMR studies of carbohydrate hydration

Measurement of water oxygen-17 relaxation times has been used to provide information about the hydration behaviour of some carbohydrates in aqueous solution. While a solvent water molecule is 'bound' to the solute, its reduced rotation is reflected in the solvent n.m.r. relaxation. The experimental data are consistent with a fast-exchange two-state model of carbohydrate hydration. Such a model allows calculation of the activation energies for the molecular processes involved in spin relaxation of bound water. The activation energies provide information about the specific hydration properties of individual sugars. Dynamic hydration numbers of five aldohexoses and two methyl glucopyranosides have been determined. These hydration numbers correlate well with hydration parameters derived from a number of techniques. Overall, the results provide additional support for a stereospecific model of monosaccharide hydration.