Experimental determination of structural relaxation in trehalose-water solutions by inelastic ultraviolet scattering

We report Brillouin ultraviolet scattering measurements on trehalose-water solutions in a wide range of concentrations (? = 0-0.74). A complete set of data as a function of temperature (-10 °C?T?100 °C) has been obtained for each concentration. The T-? evolution of the system has been analyzed in terms of energy position and linewidth of inelastic peaks. These results have been used to derive the structural relaxation time of the system, ?, which was found in the tens of ps timescale. Its T-dependence can be described with an Arrhenius activation law, and, most importantly, a significant slowing down of the relaxation dynamics has been observed as trehalose concentration was increased. At low-?, the activation energy of the relaxation has been found to be consistent with literature data for pure water, and comparable with intermolecular hydrogen bond (HB) energy. This evidence strongly supports the hypothesis that the main microscopic mechanism responsible for the relaxation process in trehalose solutions lies in the continuous rearrangement of the HB network. Finally, the results are discussed in terms of the evolution of the system upon increasing trehalose concentration, in order to provide a complete description of the viscoelastic stiffening in real biological conditions.