Figure 6

Glycopeptide enrichment by PEI-g-DF@mSiO₂@SiO₂@Fe₃O₄ microspheres. (a) Schematic illustration of the enrichment strategy based on a dispersive solid-phase extraction (dSPE) mode. (b) Possible binding mode of a typical bi-antennary sialo-glycopeptide on the polyethyleneimine-grafted-L-aspartate-L-phenylalanine dimethyl ester (PEI-g-DF) polymer surface (blue layer); hydrogen bonds are indicated by red dashed lines. (c) Mass spectra of glycopeptides enriched with our material from tryptic digests of fetuin and bovine serum albumin (BSA) at a molar ratio of 1:10. Detected glycopeptides are marked with their glycan structures: blue ▪: GlcNAc; green ●: mannose; yellow ●: galactose; red ▴: fucose; purple ♦: Neu5Ac. These glycopeptides were identified based on the ‘UniProt’ (peptide sequence) and ‘GlycoMod’ (glycan structures) databases. The corresponding serial numbers of the mass spectrum (MS) signals are labeled in the square brackets. A high proportion of the sialo-N-linked glycopeptides with core glycan fragment were identified, which validated our glycan-targeted design. More detailed information, including the m/z values of the identified glycopeptides and peptide sequences, is displayed in Supplementary Table 1.