1 research outputs found
Dynamics of Hydration Water in Sugars and Peptides Solutions
We
analyzed solute and solvent dynamics of sugars and peptides
aqueous solutions using extended depolarized light scattering (EDLS)
and broadband dielectric spectroscopies (BDS). Spectra measured with
both techniques reveal the same mechanism of rotational diffusion
of peptides molecules. In the case of sugars, this solute reorientational
relaxation can be isolated by EDLS measurements, whereas its contribution
to the dielectric spectra is almost negligible. In the presented analysis,
we characterize the hydration water in terms of hydration number and
retardation ratio ξ between relaxation times of hydration and
bulk water. Both techniques provide similar estimates of ξ.
The retardation imposed on the hydration water by sugars is ∼3.3
± 1.3 and involves only water molecules hydrogen-bonded (HB)
to solutes (∼3 water molecules per sugar OH-group). In contrast,
polar peptides cause longer range perturbations beyond the first hydration
shell, and ξ between 2.8 and 8, increasing with the number of
chemical groups engaged in HB formation. We demonstrate that chemical
heterogeneity and specific HB interactions play a crucial role in
hydration dynamics around polar solutes. The obtained results help
to disentangle the role of excluded volume and enthalpic contributions
in dynamics of hydration water at the interface with biological molecules