Water dynamics in the hydration shells of biological and non-biological polymers.

The dynamics of water at supercooled temperatures in aqueous solutions of different types of solutes has been deeply analyzed in the literature. In these previous works and in most of the cases, a single relaxation of water molecules is observed. In this work, we analyze the dynamics of water in solutions for which a dual relaxation of water molecules is experimentally measured. We discuss the criteria for observing these two water relaxations in these specific solutions and their most likely origins. We also discuss how these two water relaxations relate to the relaxation behavior of bulk water and how the slower one is coupled to the solute dynamics and is essential for the dynamics and functional properties of proteins.