A Neu5Acα2-6LacNAc (Neu5Acα2-6Galβ1-4GlcNAc) trisaccharide equipped with an azide-functionalized linker through a hydrophilic triethylene glycol (PEG3) spacer. The terminal azide can be covalently coupled to alkyne partners via copper-catalyzed azide-alkyne cycloaddition (CuAAC), or to dibenzocyclooctyne (DBCO) and related strained alkynes using copper-free click chemistry, forming stable 1,2,3-triazole linkages. Neu5Acα2-6LacNAc is a ligand for Siglecs and for influenza hemagglutinin, particularly the human-adapted strains that preferentially recognize α2-6-linked sialic acids. This probe can be used as a soluble inhibitor or immobilized on plates or sensors to investigate binding. Neu5Acα2-6LacNAc is also a substrate for sialidases, enabling its use in enzyme activity assays and in studies of sialic acid turnover.