SLOW DYNAMICS OF SUPERCOOLED TREHALOSE HYDRATION WATER IN COMPARISON WITH BULK WATER

Trehalose aqueous solutions are relevant in many technological applications,for example in cryopreservation of biomolecules. It is known that the presence of thisdisaccharide is able to slow down the dynamics of nearby water molecules and to modifytheir spatial rearrangement, nevertheless, a complete understanding of the properties ofwater-trehalose solutions and of trehalose cryoprotective properties is still lacking. Herewe discuss recent molecular dynamics simulation results of water-trehalose solutions,performed at different temperatures upon cooling, and we compare the results with thebehavior of the bulk phase. In particular we focus on the dynamical properties of hydrationwater, i.e., the water molecules in the hydration shell of the disaccharide. Hydration watershows a sub-diffusive behavior with respect to bulk water, the same structural relaxationtypical of glass formers liquids, albeit slightly slower than in the bulk, and an additionalrelaxation process at longer timescales completely absent in the bulk. The analysis ofhydrogen bond autocorrelation functions allows to connect the structural and long relaxationprocesses of hydration water to the dynamics of two distinct population of hydrogen bondsin the system, the water-water and water-trehalose hydrogen bonds.