Deuterium NMR and EPR of hydrated collagen fibers in the presence of salts

A new model for hydrated collagen fibers is postulated. According to this model, a part of the water adsorbed is bound to the collagen fiber through hydrogen bonding, and the rest is randomly reorienting. The two types of water are in chemical exchange. The observed dipolar splitting for H 2 O and quadrupolar splitting for D 2 O are time‐averaged values. The deuterium quadrupole splitting of D 2 O in oriented collagen fibers decreases in the presence of salt. The phenomenon can be explained either by a change in the structure of collagen or by the blocking of the water binding sites by the ions. In the EPR spectra of collagen presoaked in Mn(II) and Cu(II) sulfates, the line widths decrease with the increase of water content, indicating the coordination of the cations to water. The change in the hyperfine splitting (from 70 gauss in dry fibers to 96 gauss in fibers equilibrated at 100% RH) of Mn(II) with water content is explained by the change in the symmetry of its environment.