Linkage-selective derivatization for glycosylation site- and glycoform-specific characterization of sialic acid isomers using mass spectrometry.

Here, we developed a linkage-selective derivatization approach for the differentiation and relative quantification of α-2,3- and α-2,6-linked sialic acids in a site- and glycoform-specific manner. Linkage-selective derivatization with isotope molecules discriminates the isomeric glycopeptides easily using MS and provided a tool for biomarker discovery using the quantitative analysis of isomeric glycopeptides.