Stable-isotope-assisted NMR studies on C-13-enriched sialyl Lewis(x) in solution and bound to E-selectin

We report the determination of the solution structure and dynamics of C-13- enriched Neu5Ac alpha 2-3Gal beta 1 -4(Fuc alpha 1-3)GlcNAc (sialyl Lewis(x )), together with its bound-state conformation in association with E-select in. The availability of C-13-enriched material enabled both the measurement of trans-glycosidic C-13-C-13 coupling constants as conformational probes in the tetrasaccharide and the application of three-dimensional nuclear Ove rhauser effect C-13-H-1 heteronuclear single-quantum correlation experiment s for the measurement of intramolecular transferred nuclear Overhauser effe cts (TRNOEs) characterizing the bound-state conformation of the ligand. The additional dispersion afforded by the third (C-13) dimension permitted str aightforward identification and quantitation of these TRNOEs, and several T RNOEs were identified that had not previously been reported. The bound-stat e conformation of the ligand, determined by use of a heteronuclear full-rel axation matrix analysis of the TRNOE data, differs significantly from that reported in previous studies.