Proton magnetic relaxation dispersion in aqueous biopolymer systems

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Abstract
Measurements of the proton spin-lattice relaxation rates for Larmor frequencies between 200 Hz and 60 MHz and of the spin-spin relaxation rates at 2 kHz and 25 MHz have been performed in three types of polymerized fibrin. The influence of aggregation-induced macromolecular dynamical hindrance on the relaxation behaviour is analysed and discussed. Special attention is given to the relaxation behaviour at low magnetic field, which results from a combined effect of macromolecular reorientation, hydration and chemical exchange between free and bound water. Further support is given to an overall relaxation scheme involving slow exchanging protein protons as well as slightly anisotropically bound water molecules. Bound water protons appear to relax mainly by intramolecular interaction and to exchange with free water protons through a thermally activated process with activation energy of ca 7·5 kJ mol-1.