Identifying Specific and Differentially Linked Glycosyl Residues in Mammalian Glycans by Targeted LC-MS Analysis

Glycans, which are widespread in nature, consist of a large number of monosaccharides linked via glycosidic bonds. Due to the complex nature of glycan structures on glycoproteins, assessing the configuration and positions of the glycosidic linkages of a glycan is a subject of considerable interest. In this study, a method for accomplishing this using partially O-methylated alditols (PMAs) from glycans combined with LC-MS analysis is reported. N-Glycans were first per methylated with methyl iodide, and the levels of methylation were further confirmed by MALDI-TOF. PMAs were then produced via complete hydrolysis and reduction. PMAs derived from Fetuin N-glycan and Lewisa antigen carbohydrates were successfully detected by LC-MS analysis. This analysis can be performed without the need for an additional derivatization step for GC analysis, and should be suitable for use in conjunction with a LC-MS-based analysis platform.