Relationship between structure and three-bond proton–proton coupling constants in glycosaminoglycans Original Research Article

Theoretical calculations using the DFT theory at the B3LYP/6-311++G∗∗ level were used to determine the molecular geometry of various glycosaminoglycan (GAG) molecules. Three-bond proton–proton spin–spin coupling constants (3JH–C–C–H) were then computed and compared with the published experimental data of selected mono- and disaccharides. The computed 3JH–C–C–H values showed a strong dependence on the molecular geometry and varied up to 12 Hz. This dependence was expressed in a simple analytical form relating 3JH–C–C–H and torsion angles. The population of conformers in heparin and other biologically active GAGs has also been estimated using the computed coupling constants.