Slowing down of water dynamics in disaccharide aqueous solutions

TL;DR

This study combines molecular dynamics simulations and Raman experiments to show that disaccharides like trehalose, maltose, and sucrose slow water dynamics in solutions, especially at high concentrations, which may stabilize proteins.

Contribution

It provides a detailed analysis of how disaccharides influence water dynamics and hydrogen bonding, highlighting the role of hydrogen bond network percolation in stabilization effects.

Findings

Water diffusion decreases with sugar concentration.

Hydrogen bond lifetimes increase with sugar concentration.

Percolation of sugar hydrogen bonds amplifies water slowdown.

Abstract

The dynamics of water in aqueous solutions of three homologous disaccharides, namely trehalose, maltose and sucrose, has been analyzed by means of molecular dynamics simulations in the 0-66 wt % concentration range. The low-frequency vibrational densities of states (VDOS) of water were compared with the susceptibilities chi" of 0-40 wt % solutions of trehalose in D2O obtained from complementary Raman scattering experiments. Both reveal that sugars significantly stiffen the local environments experienced by water. Accordingly, its translational diffusion coefficient decreases when the sugar concentration increases, as a result of an increase of water-water hydrogen bonds lifetimes and of the corresponding activation energies. This induced slowing down of water dynamics, ascribed to the numerous hydrogen bonds that sugars form with water, is strongly amplified at concentrations above 40 wt % by the percolation of the hydrogen bond network of sugars, and may partially explain their well-known stabilizing effect on proteins in aqueous solutions.