Dielectric relaxation of hydration water in the Dickerson–Drew duplex solution probed by THz spectroscopy

Abstract The contribution of water to DNA conformational change, DNA–protein interactions, and DNA–ligand recognition has been underlined. Here, we investigate the relaxation process of water around the Dickerson–Drew B-DNA duplex using terahertz spectroscopy. By controlling the DNA concentration, the relaxation time for water reorientation and the width of the DNA hydration layer are determined. We found that a layer of weakly bound hydration water, with a relaxation time of 11.6 ps, extends 7.6 A from the tight-binding water layer. This result demonstrates that a shell of hydration water, with reorientation time on the order of tens of picoseconds, exists beyond the structurally integrated water usually observed around DNA.