NMR-STUDY OF COLLAGEN WATER INTERACTIONS

A proton magnetic resonance study of different cross-linked collagens was performed as a function of water content and temperature. Collagen s from three connective tissues (calf, steer, and cow) were chosen acc ording to the different number of nonreducible multivalent cross-links , which increases during the life of animal. Samples were hydrated und er five well-defined water activities (A(w)) ranging from 0.44 to 0.85 . The transverse and cross-relaxation times of water protons were stud ied as a function of temperature from -20 up to 100 degrees C. From th e temperature dependence of relaxation rates, the dynamics of water mo lecules can be described according to different processes: exchange of protons at the higher temperatures and dipole-dipole interactions tha t prevail at the lower temperatures. The exchange processes are analyz ed as a function of the residence lifetime of water molecules at the p rotein interface and of the transfer of spin energy from water protons to macromolecule protons. The proton dipole-dipole interactions are r elated to the relaxation parameters of protein and water protons. All the relaxation parameters showed specific behavior for the 0.44 water activity for every tissue. The collagen tissue from calf also showed d istinct behavior in comparison with other tissues. (C) 1994 John Wiley & Sons, Inc.