Conformational kinetics of disaccharides in aqueous solutions.

Between 100 kHz and 2 GHz ultrasonic attenuation spectra of disaccharides in water have been measured at 25 degrees C. Some additional measurements have been performed at different temperatures between 10 and 35 degrees C and as a function of saccharide concentration c (0.5 mol/l</=c</=1.8 mol/l). The analytical description of the spectra in terms of relaxation spectral functions revealed four relaxation regimes. Three relaxation regions correspond to such revealed by monosaccharides in solution. These relaxations reflect a pseudorotation, an exocyclic hydroxymethyl group rotation, and probably a saccharide-saccharide association. The relaxation term with relaxation time between 3.6 and 19 ns (25 degrees C) is characteristic for the disaccharide solutions. It has been assigned to a rotation of the disaccharide rings relative to one another.