HYDRATION OF OLIGOSACCHARIDES

The spin-lattice relaxation times, T1, of (H2O)-O-17 have been measured for aqueous solutions of 2 di-, 2 trisaccharides, alpha-, and gamma-c clodextrins as a function of the concentration at 25-degrees-C. The dynamic hydration numbers, n(DHN), for 17 sugars including monosaccharides were expressed by the linear relation of the mean number of the equatorial OH groups. The second virial coefficients showed a good correlation with n(DHN). Though the rotational correlation times, tau(c)h, of water molecules in the cosphere of sugar molecules increased with increasing the number of equatorial OH groups for monosaccharides, those for trisaccharides and cyclodextrins showed almost constant values. The relation between the values of the limiting diffusion coefficients and n(DHN) for sugars was found to be expressed by two lines with a large negative slope for mono- and di- saccharides, and a small negative slope for trisaccharides and cyclodextrins.