State of water in gelatin solutions and gels: an 1H n.m.r. investigation

Abstract According to a now well established interpretation, the network growth in gelatin gels results from a conformational coil-helix transition leading to partial renaturing of native collagen. Proton magnetic resonance has been used in order to elucidate the role of water in this process. Proton spin-lattice T 1 and spin-spin T 2 relaxation times, have been measured at various concentrations and quenching temperatures. The results have been interpreted within the framework of a multiphase model involving three populations of water protons in rapid exchange which are affected differently by the macromolecular network growth in the course of gelation. In particular, the model is adequate to explain the time dependence of T 2 after quenching. Our results concerning the spin-lattice relaxation of the bound water protons are in good agreement with those measured in hydrated native collagen or in agarose gels.