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One‐pot nonreductive O‐glycan release and labeling with 1‐phenyl‐3‐methyl‐5‐pyrazolone followed by ESI‐MS analysis

A novel one‐pot procedure for the nonreductive release of O‐linked glycans from glycoproteins and the simultaneous derivatization of released glycans with 1‐phenyl‐3‐methyl‐5‐pyrazolone (PMP) is described. Unlike the traditional reductive β‐elimination, which produces alditols, this new method employs PMP/ammonia aqueous solution as the reaction medium. The O‐glycans are released from glycoproteins and derivatized with PMP nonreductively, specifically, and quantitatively. Samples can be easily purified from ammonia, excess PMP, and peptide residues by evaporation, chloroform extraction, and solid‐phase extraction (SPE) column fractionation for HPLC, CE, or MS analysis. The procedure has been elaborated with two purified glycoproteins, porcine stomach mucin and bovine fetuin, and successfully applied to O‐glycan profiling of a challenging biological specimen, healthy human plasma. This new procedure has shown methodological significance in O‐glycan analysis.