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Abstract The low abundance of glycopeptides in biological samples makes it necessary to enrich them before further analysis. In this study, the polymeric hydrophilic ionic liquid-modified magnetic (Fe3O4@MPS@PMAC) nanoparticles were synthesized via a one-step reflux-precipitation polymerization. Owing to the excellent hydrophilicity and strong electrostatic interaction toward glycopeptides of the polymerized hydrophilic ionic liquid, [2-(methacryloyloxy) ethyl] trimethylammonium chloride (MAC), the synthesized Fe3O4@MPS@PMAC nanoparticles exhibited outstanding performance in glycopeptide enrichment with high detection sensitivity (10 fmol), large binding capacity (100 μg mg−1) and satisfied enrichment recovery (approximately 82%). Furthermore, the newly developed Fe3O4@MPS@PMAC nanoparticles were applied for the glycopeptide enrichment of HeLa exosome proteins. A total of 1274 glycopeptides from 536 glycoproteins were identified in three replicate analyses of 50 μg of HeLa exosome proteins. These results demonstrate the potential of Fe3O4@MPS@PMAC nanoparticles for both glycoproteomic analysis and exosome research.

Mass spectrometry (MS)-based glycoproteomics research requires highly efficient sample preparation to eliminate interference from non-glycopeptides and to improve the efficiency of glycopeptide detection. In this work, a novel MoS2/Au-NP (gold nanoparticle)-L-cysteine nanocomposite was prepared for glycopeptide enrichment. The two-dimensional (2D) structured MoS2 nanosheets served as a matrix that could provide a large surface area for immobilizing hydrophilic groups (such as L-cysteine) with low steric hindrance between the materials and the glycopeptides. As a result, the novel nanomaterial possessed an excellent ability to capture glycopeptides. Compared to commercial zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) materials, the novel nanomaterials exhibited excellent enrichment performance with ultrahigh selectivity and sensitivity (approximately 10 fmol), high binding capacity (120 mg g-1), high enrichment recovery (more than 93%), satisfying batch-to-batch reproducibility, and good universality for glycopeptide enrichment. In addition, its outstanding specificity and efficiency for glycopeptide enrichment was confirmed by the detection of glycopeptides from an human serum immunoglobulin G (IgG) tryptic digest in quantities as low as a 1:1250 molar ratio of IgG tryptic digest to bovine serum albumin tryptic digest. The novel nanocomposites were further used for the analysis of complex samples, and 1920 glycopeptide backbones from 775 glycoproteins were identified in three replicate analyses of 50 μg of proteins extracted from HeLa cell exosomes. The resulting highly informative mass spectra indicated that this multifunctional nanomaterial-based enrichment method could be used as a promising tool for the in-depth and comprehensive characterization of glycoproteomes in MS-based glycoproteomics. [ABSTRACT FROM AUTHOR]

A refined ionization model of small molecules was developed based on a unit of classic models. The ionization process was divided into three sub-processes of diffusion, charge transfer, and ion evaporation. Based on the equations, the impact of a single process and multiprocesses on response was verified by employing special samples, and the relative evaporation energies of several pair of samples were calculated. This model is sensitive to slight differences in ionization energy and allows distinction of the ionization differences during each sub-process. [ABSTRACT FROM AUTHOR]