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

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.