NUCLEAR-MAGNETIC-RESONANCE RELAXATION OF GLYCOGEN H1 IN SOLUTION

The NMR relaxation properties of the H1 proton of oyster glycogen in D 2O and H2O solutions have been studied using nonselective, semiselecti ve, and selective inversion recovery and Hahn spin-echo pulse sequence s. The data were analyzed in terms of an isotropic, rigid-rotor dipole -dipole model including cross-relaxation. At 8.4 T in D2O, rho = 5.4 /- 0.4 s-1 and sigma = -4.5 +/- 0.4 s-1. The large, negative sigma val ue is consistent with strong cross-relaxation and a long correlation t ime. The relaxation data can be explained by a single correlation time , tau(c) = 2.7 x 10(-9) s, indicating significant internal mobility. W ith this value of tau(c), and assuming that the structure of the gluco se moieties was the same as in alpha-D-glucose crystals, the dipole su m contributing to T1 relaxation was calculated. The intra-ring relaxat ion was dominated by dipole fields from the H2 proton, but these only accounted for approximately 18% of the total relaxation. Most of the r elaxation comes.from inter-glucose relaxation. From modeling, this is dominated by the H4' across the alpha-1,4-glycosidic bond. The H1 long itudinal relaxation rates were significantly enhanced in H2O compared with D2O. This enhancement is not due to direct dipolar interaction be tween H1 and bulk water. Transverse relaxation rates were not signific antly enhanced in H2O.