PROTON NMR RELAXATION STUDIES OF AQUEOUS POLYSACCHARIDE SYSTEMS

The major features of NMR transverse water proton relaxation in polysaccharide solutions and gels can be quantitatively interpreted in terms of fast chemical exchange between water and polysaccharide hydroxyl protons. The water proton relaxation is found to be a useful monitor of the mobility and state of aggregation of the polysaccharide chains and to complement information from high-resolution NMR spectroscopy. In carrageenan gels there is evidence for microheterogeneity and this gives additional diffusive dephasing contributions. Although there is evidence that polysaccharides influence the state of the water around them (the so-called "bound" water concept), the results obtained suggest that this affects the proton transverse relaxation in a minor way compared to the potent effect of the chemical exchange mechanism.