Dielectric studies of protein hydration and hydration-induced flexibility.

Dielectric measurements, as a function of hydration, are reported for collagen, cytochrome-c, elastin and lysozyme powders. The hydration dependence of the dispersion that occurs in the frequency range between 10 kHz and 10 GHz has been used to identify two classes of protein-bound water molecules (namely, rotationally hindered or unhindered), as well as the hydration level for the onset of an increasing protein flexibility. Such studies can aid an understanding of the relationship between enzyme activity and structural flexibility, and of hydration-induced changes in the structure and dynamics of protein structures.