Glycan profiling: label-free analysis of glycoproteins.

Profiling of glycans requires both characterization of structure and determination of the relative -abundance of each glycan. Label-free approaches enable facile and efficient profiling, while detailed structures and precise quantitation require derivatization. For glycan profiling by mass spectrometry, correlating the ion abundance in the mass spectrum to the content of each glycoform in the sample is acceptable, when one has adequate knowledge of ionization mode and ionization efficiency in mass spectrometry. Glycopeptide is a suitable analyte for this label-free approach.