Hydrated elastin: Dynamics of water and protein followed by dielectric spectroscopies

The dielectric properties of elastin were investigated at different levels of hydration and specifically at the limit of freezable water apparition. The quantification of freezable water was performed by Differential Scanning Calorimetry (DSC). Two dielectric techniques were used to explore the dipolar relaxations of hydrated elastin: dynamic dielectric spectroscopy (DDS), performed isothermally with the frequency varying from 10 to 3 10 Hz, and the technique of thermally stimulated depolarization currents (TSDC), an isochronal spectrometry running at variable temperature, analogous to a low frequency spectroscopy (10–10 Hz). A complex relaxation map was evidenced by the two techniques. Assignments for the different processes can be proposed by the combination of DDS and TSDC experiments and the determination of the activation parameters of the relaxation times. As already observed for globular proteins, the concept of ‘‘solvent-slaved’’ protein motions is checked for the fibrillar hydrated elastin.