The use of NMR residual dipolar couplings in aqueous dilute liquid crystalline medium for conformational studies of complex oligosaccharides

C–H dipolar coupling values were measured for a natural-abundance sample of the pentasaccharide β-d-Galp-(1→3)-[α-l-Fucp-(1→4)]-β-d-GlcNAcp-(1→3)-β-d-Galp-(1→4)-β-d-Glcp (‘lacto-N-fucopentaose 2’) (LNF-2), in a 7.5% solution of dimyristoyl phosphatidylcholine–dihexanoyl phosphatidylcholine bicelle liquid crystals oriented in the NMR magnetic field. Interpretation of the dipolar coupling data and NOE confirms the conformational model for the Lewisa trisaccharide epitope based on NOE, molecular dynamics simulations, and scalar coupling data and provided new structural information for the remaining residues of the pentasaccharide. Since residual dipolar coupling provides information on long-range order, it is a valuable complement to other types of NMR data such as NOE and scalar coupling for exploring conformations of complex oligosaccharides.