Calorimetric studies of elastin solvation.

The interaction of ox ligamentum nuchae elastin (native, purified and soluble) with four different solvents was investigated by Differential Scanning Calorimetry. The freezable solvent content was determined, at different total solvent contents, from the melting endotherms, and the amount of unfreezable solvent was obtained by extrapolation. For two bifunctional solvents, water and ethylene glycol, the molar ratio "bound solvent/elastin residue" was the same for all the elastin samples investigated, and very close to 1.5. This result is identical to that obtained by other workers for the "water/CO-NH group" of synthetic amorphous polyamides, and it can suggest that the hydration of elastin is interpretable on the basis of a similar model. The model is based on a direct interaction of water with the peptide group, and suggests that 0.5 moles of water are strongly bound, and 1.0 moles are loosely bound to the CO-NH group. The ratio "bound water/elastin residue" is larger for the soluble beta elastin. Different molar ratios are also obtained for monofunctional solvents such as methanol and trifluoroethanol.