An integrated quasi-elastic light-scattering, pulse-gradient-spin-echo study on the transport properties of alpha,alpha-trehalose, sucrose, and maltose deuterium oxide solutions

A study on D20 solutions of trehalose, maltose, and sucrose have been perfo rmed by using quasi-elastic light-scattering (QELS) and H-1 and H-2 pulse-g radient-spin-echo NMR (PGSE-NMR). The self-diffusion coefficient of disacch aride (D) and the apparent diffusion coefficient D-app have been obtained a s a function of disaccharide weight fraction c and temperature (20-60 degre esC). Hydrodynamic radii at infinite dilution have been evaluated. In case of trehalose and sucrose a model of monodisperse hard spheres has been used to interpret the concentration dependence of D and D-app in the dilute reg ion (c less than or equal to 0.1), thus obtaining the values of the hydrody namic radii together with the diffusing particles volume fractions as a fun ction of c and T. The invariance of the hydrodynamic radii and the agreemen t with the model suggest that T and c neither induce self-aggregation of th e sugars nor affect sensitively their structure and hydration. The self-dif fusion coefficient of D2O (D-s) at 20 degreesC has also been measured for t he DO solutions of the three sugars. By following an interpretation commonl y used to rationalize the self-diffusion coefficient of small molecules in colloidal systems, obstruction and hydration of disaccharide have been invo ked to explain the decrease of D, as a function of c. The hydration numbers rank trehalose > maltose > sucrose has been observed in agreement with dat a reported in the literature.