Conformational flexibility of disaccharides investigated by multiple fieldcarbon-13 nuclear spin relaxation

Multiple-field carbon-13 NMR relaxation studies were performed on four disa ccharides with different sugar residues, anomeric configurations and substi tution positions. Measurements were made in dimethyl sulfoxide at 300 K, le ading to conditions outside the extreme narrowing regime. Global correlatio n times differed between the disaccharides and scaled well with the number of hydroxyl groups of the disaccharides that can hydrogen bond to solvent. The Lipari-Szabo generalized order parameter was similar for the disacchari des with an average of S-2 = 0.75 +/- 0.03 when a carbon-proton distance of 109.8 pm was used. However, the flexibility at the disaccharide level is e xpected to be more restricted (higher value of S-2) since a longer carbon-p roton distance is judged to be more appropriate. Copyright (C) 1999 John Wi ley & Sons, Ltd.