Dynamical Behavior of Carbohydrates As Studied by Carbon-13 and Proton Nuclear Spin Relaxation

Abstract

Variable-field carbon-13 and proton relaxation data are reported for two saccharides: a monosaccharide, 1,6-anhydro-β-d-galactopyranoside; and a disaccharide, methyl 3-O-α-d-mannopyranosyl-β-d-glucopyranoside. Carbon-13 measurements were perfomed at two fields, 4.7 and 9.4 T, and at 268, 288, and 303 K for the monosaccharide and at 268, 288, 303, and 323 K for the disaccharide. Proton cross-relaxation measurements were performed at three magnetic field strengths, 7.05, 9.4, and 11.75 T, and at several temperatures, 268, 288, and 303 K for the monosaccharide and 268, 282, 288, and 323 K for the disaccharide. The carbon-13 results were analyzed with the Lipari−Szabo “model-free” approach to obtain estimates of the global correlation times and order parameters. The monosaccharide was found to be very rigid, with S2 = 0.91, while the disaccharide showed some internal motions reflected in a lower order parameter, S2 around 0.8. The intra-ring proton cross-relaxation could be explained by the motional paramete...