Effect of NaCl on Water Activity and Hydration Water Dynamics in Proteins by Quasielastic Neutron Scattering

Effect of NaCl on a protein hydration is of interest in interdisciplinary fields such as food science and extreme environment biology. Here, the protein hydration water dynamics with various NaCl concentrations at a constant water activity(A(w)) by incoherent quasielastic neutron scattering (iQENS) are examined. Under the same A(w), the water content increases with increasing NaCl concentration. iQENS analysis of these samples shows no significant difference in the dynamics of water molecules despite of the difference of water content. This suggests that the hydration water dynamics should be suppressed in the present of NaCl. Water dynamics is affected by NaCl, but independent of this, there is a universal correlation between A(w) values and water molecule dynamics.