Nature of the water specific relaxation in hydrated proteins and aqueous mixtures

The influence of water on protein properties

“…We mention, together with the violation of the Stokes Einstein law, the orientational-translational decoupling (the translation-rotation paradox 18 ), the splitting of the relaxation into the primary (α) and secondary relaxation times, the onset of dynamical heterogeneities and of the Boson peak (hypothesized for bulk water 14 and observed in the confined one 15 ). The FSDC appears to be of importance also for hydrated proteins; the phenomenon can be observed not only for confined water but also for hydrated biosystems such as proteins, 17,[19][20][21][22][23][24] where the Boson peak has been also observed. 16,25 For clarity we note that, besides these many signatures on the FSDC importance in material science, it has been questioned especially in the case of the water-protein systems.…”

Dielectric study on temperature–concentration superposition of liquid to glass in fructose–water mixtures

“…The relaxation time and strength of the β relaxation change from having weaker temperature dependences below T g to having stronger ones above T g . These changes in the behaviors of the β relaxation upon crossing T g are the same as those found for the ν relaxation [9,10], which is the primary relaxation process of water originating from the local motion of water molecules in various other aqueous mixtures with hydrogen-bonded molecular liquids, polymers, and nanoporous systems [9][10][11][12][13]. The properties of the relaxation time, τ β , and relaxation strength, Δε β , of the secondary β relaxation above and below T gα for fructose-water mixtures of all concentrations have been found to be the same as those of the ν relaxation observed in aqueous systems and the JG relaxation observed in binary mixtures of van der Waals liquids.…”

“…These similarities in the properties suggest that the secondary relaxation in fructosewater mixtures is also the ν relaxation of water [8]. The α and ν relaxations are related and cannot be considered separately [10,12]. This leads to the interpretation of the β relaxation as a precursor of the many-body relaxation process, which evolves with time culminating in the α relaxation of hydrated fructose.…”

Dynamics and Glass Transition of Aqueous Solutions of Molecular Liquid, Polymer, and Protein Studied by Broadband Dielectric Spectroscopy

“…Despite the differences in the water content and molecular structure of the solutes (including the resulting difference in T g ) in the various aqueous solutions, the relaxation attributed to the motion of water molecules observed in all the solutions showed many common characteristics [53][54][55][56]. This water relaxation is called hydration water relaxation or water-specific relaxation [57]. Here, we call it ν-relaxation [55], ν being the initial letter of νερo, which means water in Greek.…”