Hydration properties of carbohydrates: A clue from molecular dynamics

A molecular dynamics (MD) simulation study is presented for the dynamics of the polarizability anisotropy of pure water and of water- trehalose solutions as a function of concentration. The calculated time correlation functions (TCF) of the water collective polarizability for the different mixtures are compared and analyzed in terms of two distinct relaxation dynamics in the picoseconds timescale. The two processes have been attributed to the dynamics of bulk and hydration water molecules, respectively, with a retardation factor similar to 5. The whole picture has been confirmed by the further separation of the total water TCFs into the ones arising from bulk, hydration molecules and a cross term between the two, that allowed a separate estimate of the two relaxation times.