Facile and easily popularized synthesis of l-cysteine-functionalized magnetic nanoparticles based on one-step functionalization for highly efficient enrichment of glycopeptides

Protein glycosylation is one of the most important post-translational modifications. Also, efficient enrichment and separation of glycopeptides from complex samples are crucial for the thorough analysis of glycosylation. Developing novel hydrophilic materials with facile and easily popularized synthesis is an urgent need in large-scale glycoproteomics research. Herein, for the first time, a one-step functionalization strategy based on metal-organic coordination was proposed and Fe3O4 nanoparticles were directly functionalized with zwitterionic hydrophilic l-cysteine (L-Cys), greatly simplifying the synthetic procedure. The easily synthesized Fe3O4/L-Cys possessed excellent hydrophilicity and brief composition, contributing to affinity for glycopeptides and reduction in nonspecific interaction. Thus, Fe3O4/L-Cys nanoparticles showed outstanding sensitivity (25 amol/μL), high selectivity (mixture of bovine serum albumin and horseradish peroxidase tryptic digests at a mass ratio of 100:1), good reusability (five repeated times), and stability (room temperature storage of 1 month). Encouragingly, in the glycosylation analysis of human serum, a total of 376 glycopeptides with 393 N-glycosylation sites corresponding to 118 glycoproteins were identified after enrichment with Fe3O4/L-Cys, which was superior to ever reported L-Cys modified magnetic materials. Furthermore, applying the one-step functionalization strategy, cysteamine and glutathione respectively direct-functionalized Fe3O4 nanoparticles were successfully synthesized and also achieved efficient glycopeptide enrichment in human serum. The results indicated that we have presented an efficient and easily popularized strategy in glycoproteomics as well as in the synthesis of novel materials.