Terahertz spectroscopic study of ion effects on protein hydration

Effects of salts on the dynamical properties of hydration water of protein in aqueous solutions are studied using high-precision terahertz spectroscopy. Kosmotropic anions in the well-known Hofmeister series are found to decrease hydration water, and chaotropic anions increase it. This result is consistent with a theoretical model which describes the ion effects on hydration of proteins in terms of the hydrogen-bonding network around the protein.