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 beta-D-Galp-(10 --> 3)-[alpha-L-Fucp-(1 --> 4)]-beta-D -GlcNAcp-(1 --> 3)-beta-D-Galp-(1 --> 4)-beta-D-Glcp ('lacto-N-fucopentaose 2') (LNF-2), in a 7.5% solution of dimyristoyl phosphatidylcholine-dihexan oyl phosphatidylcholine bicelle liquid crystals oriented in the NMR magneti c field. Interpretation of the dipolar coupling data and NOE confirms the c onformational model for the Lewis(a) trisaccharide epitope based on NOE, mo lecular dynamics simulations, and scalar coupling data and provided new str uctural information for the remaining residues of the pentasaccharide. Sinc e 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 co upling for exploring conformations of complex oligosaccharides. (C) 2000 El sevier Science Ltd. All rights reserved.