C-13 NUCLEAR-MAGNETIC-RESONANCE RELAXATION OF AMYLOSE AND DYNAMIC BEHAVIOR OF THE HYDROXYMETHYL GROUP

The backbone rearrangement and the motion of the exocyclic hydroxymethyl group of amylose in dimethylsulfoxide using C-13 NMR relaxation has been evaluated. The Dejean-Laupretre-Monnerie model appears to be a reasonable basis for the interpretation of the experimental relaxation data corresponding to C(1) to C(5) in the glucopyranose residue. However, the jump model between two preferred conformations provides a more realistic description of the hydroxymethyl group internal motion. The relation between the lifetimes of the states was tau-A = 3-tau-B, indicating that the conformational distribution is gauche-gauche (60%) vs gauche-trans (40%).