Fig. 4.

Advantage of permethylation of glycan in the differentiation of glycan isomers via CID MSⁿ. The m/z value of sodium adduct of permethylated glycans and native glycans of N-glycan Man₅GlcNAc₂ (in brackets) which are provided under each oligosaccharide fragments shows that only MSⁿ of permethylated glycans possess key fragments (in bold) that can help to differentiate isomers A and B. The circles superimposing the bonds mean that the oxygen atoms of these glycosidic bonds are included in the fragment, i.e., they are Y-ions (see Fig. 9B) [41]