NMR investigation of oligosaccharide conformation using dipolar couplings in an aqueous dilute liquid crystalline medium

Abstract

The tetrasaccharide lacto-N-neotetraose β-D-Galp-(1→4)-β-D-GlcpNAc-(1→3)-β-D-Galp-(1→4)-D-Glcp was dissolved in a dilute mixture of dimyristoyl- and dihexanoylphosphatidylcholine in deuterium oxide and 1J(C,H) spin–spin coupling constants were measured in an isotropic solution at 25°C. On raising the temperature to 38°C, an ordering of the system occurs which permits determination of dipolar couplings. An energy mini-mized molecular mechanics model was generated showing that the molecule is anisotropic and can be treated as a cylinder. A fit of the expression for the carbon–proton dipolar couplings in a uniaxial molecule in a uniaxial liquid crystal revealed good agreement with experimental data, emphasizing the future potential of the method in studies of carbohydrate conformation. © 1998 John Wiley & Sons, Ltd.