Highly efficient enrichment of N-linked glycopeptides using a hydrophilic covalent-organic framework

The enrichment of glycopeptides plays an important role in glycoproteomics. In this paper, a covalent-organic framework called TpPa-1, synthesized by the Schiff base reaction of 1,3,5-triformylphloroglucinol and paraphenylenediamine, was first successfully utilized as a hydrophilic porous material for N-linked glycopeptide enrichment. Using this material, interference from non-glycopeptides could be efficiently eliminated, which facilitated the mass spectrometry detection of glycopeptides. By capturing N-linked glycopeptides from tryptic digests of human IgG, our method was proved to have high sensitivity at the femtomole level. And it showed superior selectivity for glycopeptides even when non-glycopeptides were 1000 times more concentrated. Due to the strong covalent bonds, this material possessed good stability and could be repeatedly used for at least 10 times. The ultra-low mass density and abundant binding sites also provided it with high binding capacity (178 mg g^-1, IgG/TpPa-1). Moreover, N-linked glycopeptides were easily enriched by this material from only 10 μL human serum, which demonstrated its potential in pretreatment of complex biological samples.