Mass spectrometry (MS) has become an indispensable tool for analyzing post translational modifications of proteins, includingN-glycosylated molecules. Because most glycosylation sites carry a multitude of glycans, referred to as "glycoforms," the purpose of anN-glycosylation analysis is glycoform profiling and glycosylation site mapping. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has unique characteristics that are suited for the sensitive analysis ofN-glycosylated products. However, the analysis is often hampered by the inherent physico-chemical properties ofN-glycans. Glycans are highly hydrophilic in nature, and therefore tend to show low ion yields in both positive- and negative-ion modes. The labile nature and complicated branched structures involving various linkage isomers make structural characterization difficult. This review focuses on MALDI-MS-based approaches for enhancing analytical performance inN-glycosylation research. In particular, the following three topics are emphasized: (1) Labeling for enhancing the ion yields of glycans and glycopeptides, (2) Negative-ion fragmentation for less ambiguous elucidation of the branched structure ofN-glycans, (3) Derivatization for the stabilization and linkage isomer discrimination of sialic acid residues.
Nishikaze, T. (2017). Sensitive and Structure-Informative N-Glycosylation Analysis by MALDI-MS; Ionization, Fragmentation, and Derivatization. Mass Spectrometry, 6(1), A0060–A0060. https://doi.org/10.5702/massspectrometry.a0060