Retardation of Bulk Water Dynamics by Disaccharide Osmolytes

TL;DR

Disaccharide osmolytes like sucrose and trehalose slow down bulk water dynamics by about 30%, potentially stabilizing proteins in biological systems by modifying water activity, as shown through ultrafast fluorescence spectroscopy.

Contribution

This study demonstrates that disaccharides reduce bulk water reorganization rates at low concentrations, revealing a possible mechanism for their bioprotective effects.

Findings

Disaccharides decrease water reorganization rate by approximately 30%.

The retardation occurs at low concentrations (0.1M and 0.25M).

Trehalose is more effective than sucrose in reducing water dynamics.

Abstract

The bioprotective nature of disaccharides is hypothesized to derive from the modification of the hydrogen bonding network of water which protects biomolecules through lowered water activity at the protein interface. Using ultrafast fluorescence spectroscopy we measured the relaxation of bulk water dynamics around the induced dipole moment of two fluorescent probes (Lucifer Yellow Ethylenediamine and Tryptophan). Our results indicate a reduction in bulk water reorganization rate of approximately of 30%. We observe this retardation in the low concentration regime measured at 0.1M and 0.25 M, far below the onset of glassy dynamics. This reduction in water activity could be significant in crowded biological systems, contributing to global change in protein energy landscape, resulting in a significant enhancement of protein stability under environmental stress. We observed similar dynamic reduction for two disaccharide osmolytes, sucrose and trehalose, with trehalose being the more effective dynamic reducer.