Solvation dynamics of biomolecules: modeling and terahertz experiments.

The role of water in biomolecule dynamics has attracted much interest over the past decade, due in part to new probes of biomolecule-water interactions and developments in molecular simulations. Terahertz (THz) spectroscopy, among the most recent experimental methods brought to bear on this problem, is able to detect even small solute induced changes of the collective water network dynamics at the biomolecule-water interface. THz measurements reveal that proteins influence up to 1000 water molecules in their surroundings, and that even small saccharides influence the dynamics of hundreds of surrounding water molecules. The THz spectrum of a protein is sensitive to mutation and depends on the surface charge and flexibility of the protein. Influence on the solvation shell appears most pronounced for native wildtype proteins and decreases upon partial unfolding or mutation. THz spectra of solvated saccharides reveal that the number of water molecules coupled dynamically to a saccharide, forming a dynamical hydration shell around it, is related to the number of exposed oxygen atoms on the solute. The thickness of this layer appears correlated with the bioprotection efficiency of the saccharide. All findings support the thesis of a long-range dynamic coupling between biomolecule and solvent.