Advances in Analysis of Linkage Isomers of Sialylated N-Glycans by Mass Spectrometry

Protein glycosylation occurs during and after the translation process, and glycosylation will diversify the function of the protein. Glycosylation directly or indirectly affects the function of proteins and their interactions, and is related to a variety of human diseases. Among them, sialylated N-glycans play a key role in many important physiological and pathological processes. Sialic acid usually bonds with adjacent monosaccharides via alpha-2,3-, alpha-2,6-, alpha-2,8- or alpha-2,9- linkage. Sialylated N-glycans with different linkage always have different functions in cell activities, physiological and pathological processes of living organisms. Mass spectrometry is an important tool for the analysis of N-glycans. It can quickly and sensitively detect N-glycans. The separation and detection of sialylated N-glycans and their linked isomers can be achieved by combining chromatographic techniques and derivatization methods with mass spectrometry. In this review, we mainly focuses on alpha-2,3 and alpha-2,6-linked sialylated N-glycans, introduces their structure and different functions in cell activities and various diseases, and summarizes the analysis methods of linked isomers of sialylated N-glycans based on mass spectrometry and the application of these methods in the field of biomedicine in recent years. This review can provide new ideas and approaches for future biomedical research.