Scanning of hydrogen bonds dynamics in hydrated fibrous proteins by dielectric spectroscopies

In this study, the combination of both thermal analysis and dielectric techniques were showed to be useful to characterize a biopolymer in the hydrated state. The "filling" of the hydration shell of elastin is followed by DSC. The first hydration shell is completely "full" for 1.2-1.3 molecules of water bound to one elastin residue, when only non-freezable water covers the shell of the protein. Localized motions (at the nanometric scale), undetectable by DSC, that occur at low temperature can be observed by the combined use of DDS and TSDC. These results on hydrated elastin are a basis to help to the question- How the solvent influences the protein dynamics which still remains largely unanswered. Moreover, our experimental data could be useful for the assessment of starting conditions in molecular dynamics simulations: simulation on long polypeptide sequences of elastin could be launched with a small hydration level, typically 10%, corresponding to detectable localized reorientations of the complex water/residues in dielectric spectroscopies. At the present time we scanned the different kinds of mobility of hydrated elastin in the frozen state; the next step of the study will be performed at physiological temperature to follow the dynamics of hydrogen bonds network and protein, and to test in this case the two state model implying the dynamic exchange between bound and free water molecules.