Selenoglycosides as Lectin Ligands: 77Se-Edited CPMG-HSQMBC NMR Spectroscopy To Monitor Biomedically Relevant Interactions

Abstract

The fundamental importance of protein–glycan recognition calls for specific and sensitive high-resolution techniques for their detailed analysis. After the introduction of 19F NMR spectroscopy to study the recognition of fluorinated glycans, a new 77Se NMR spectroscopy method is presented for complementary studies of selenoglycans with optimised resolution and sensitivity, in which direct NMR spectroscopy detection on 77Se is replaced by its indirect observation in a 2D 1H,77Se HSQMBC spectrum. In contrast to OH/F substitution, O/Se exchange allows the glycosidic bond to be targeted. As an example, selenodigalactoside recognition by three human galectins and a plant toxin is readily indicated by signal attenuation and line broadening in the 2D 1H,77Se HSQMBC spectrum, in which CPMG-INEPT long-range transfer ensures maximal detection sensitivity, clean signal phases, and reliable ligand ranking. By monitoring competitive displacement of a selenated spy ligand, the selective 77Se NMR spectroscopy approach may also be used to screen non-selenated compounds. Finally, 1H,77Se CPMG-INEPT transfer allows further NMR sensors of molecular interaction to be combined with the specificity and resolution of 77Se NMR spectroscopy.