Trehalose-induced slowdown of lysozyme hydration dynamics probed by EDLS spectroscopy.

We use extended depolarized light scattering spectroscopy to study the dynamics of water in a lysozyme-trehalose aqueous solution over a broad time scale, from hundreds to fractions of picoseconds. We provide experimental evidence that the sugar, present in the ternary solution in quantity relevant for biopreservation, strongly modifies the solvation properties of the protein. By comparing aqueous solutions of lysozyme with and without trehalose, we show that the combined action of sugar and protein produces an exceptional dynamic slowdown of a fraction of water molecules around the protein, which become more than twice slower than in the absence of trehalose. We speculate that this ultraslow water may be caged between the sugar and protein surface, consistently with a water entrapment scenario. We also demonstrate that the dynamics of these water molecules gets slower and slower upon cooling. On the basis of these findings, we believe such ultraslow water close to the lysozyme is likely to be involved in the mechanism of bioprotection.