Esterification of mAb glycopeptides leads to one main product per glycoform, and enabled to differentiate 2,6 from 2,3 sialyl linkages. This fast and simple method is efficient for the analysis of sialylated glycopeptides, as it stabilizes sialic acids and transforms them into neutral residues. MALDI-MS ion abundances give a better estimate of sialylation levels for esterified that for unreacted glycopeptides by MALDI reflector positive mode. Antibody esterified ion patterns are simple and predictable.
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