Yes, N-Glycopeptide Binding Protein can bind free glycans if the GlcNAc on the reducing end is in its free form, in which the pyranose and open-ring form are in equilibrium. However, the six-member ring (pyranose) structure is required for binding. Free glycans with an entirely open-ring structure, such as those labeled by reductive amination, will not bind to N-Glycopeptide Binding Protein. Free glycans with instant labels (e.g., Waters GlycoWorks RapiFluor-MS label) will not bind to N-Glycopeptide Binding Protein.
An asparagine attached to the free glycan is not required for binding, nor is any peptide sequence.
