Conformational analysis

New conformational constraints in isotopically (13C) enriched oligosaccharides.Milton MJ, Harris R, Probert MA, Field RA, Homans SW; Glycobiology 8 (1998) 147153 PubMed 9451024 AbstractMultidimensional heteronuclear NMR studies have been applied to the resonance assignment and conformational analysis of 13Cenriched Neu5Acalpha23Galbeta14Glc. It is demonstrated that threedimensional ROESYHSQC experiments provide throughspace distance restraints which cannot be observed with conventional homonuclear 1H techniques due to resonance overlap. In particular, connectivities demonstrating the existence of the "anti" conformation about the Galbeta14Glc glycosidic linkage are unambiguously observed. It is shown that 13C isotopic enrichment of the trisaccharide at a level >95% enables straightforward measurement of transglycosidic 1H13C and 13C13C coupling constants and a Karplustype relation is derived for the latter. In total 15 conformational restraints were obtained for the trisaccharide in aqueous solution, all of which were in excellent agreement with theoretical parameters computed from a 5 ns molecular dynamics simulatio Equation^{3}J=4.4*cos^{2}(θ)1.1*cos(θ)+0.5
