The state of water on hydrated collagen as studied by pulsed NMR

The spin‐lattice relaxation time ( T 1 ) of water adsorbed on collagen fibers was determined at six frequencies and temperatures varying from 25° to −80°C. Care was taken to eliminate the contributions to the signal of protons other than those in the adsorbed water. Quantitative calculations were made on T 1 and the results were compared with the experimental data. It is suggested that a maximum of about 0.50–0.55 g water per g collagen forms a hydration layer, which cannot be frozen down to −90°C and exhibits a distribution of motional correlation times. For collagen samples containing a larger quantity of adsorbed water, the additional water molecules behave like ordinary isotropic water, having a single correlation time and a freezing temperature of about −10°C.