Ultrathin Au nanowires assisted magnetic graphene-silica ZIC-HILIC composites for highly specific enrichment of N-linked glycopeptides.

Protein glycosylation has been proven to participate in a variety of complex biological processes; however, the low abundance of glycopeptides in natural samples makes it essential to develop methods to isolate and enrich glycopeptides. In this study, a novel ultrathin Au nanowire assisted zwitterionic hydrophilic magnetic graphene oxide (GO-Fe3O4/SiO2/AuNWs/L-Cys) was synthesized with the good biocompatibility of GO, strong magnetic responses of Fe3O4, large surface area of ultrathin Au nanowires and excellent hydrophilicity of L-Cys via four simple and rapid steps. The ultrathin Au nanowires have a one-dimensional structure and were easily grafted with an abundant amount of L-Cys for the enrichment of glycopeptides. After the GO-Fe3O4/SiO2/AuNWs/L-Cys composites were applied to glycopeptide enrichment, 26 glycopeptides from a human IgG digest could be identified, with a detection limit as low as 10 fmol. Due to the abundant amount of grafted L-Cys, the composites also showed a large binding capacity (150 μg mg-1). Furthermore, the composites were applied for the analysis of real biological samples. A total of 793 glycopeptides from 467 glycoproteins were identified in three replicate analyses of 40 μg of mouse liver proteins. The results demonstrated the great potential of GO-Fe3O4/SiO2/AuNWs/L-Cys composites for the analysis of glycoproteins.