Zirconium arsenate-modified magnetic nanoparticles: preparation, characterization and application to the enrichment of phosphopeptides

Phosphorylation, one of the most important post-translational modifications of protein, plays a crucial role in a large number of biological processes. Large-scale identification of protein phosphorylation by mass spectrometry is still a challenging task because of the low abundance of phosphopeptides and sub-stoichiometry of phosphorylation. In this work, a novel strategy based on the specific affinity of zirconium arsenate to the phosphate group has been developed for the effective enrichment of phosphopeptides. Zirconium arsenate-modified magnetic nanoparticles (ZrAs-Fe3O4@SiO2) were prepared by covalent immobilization of zirconium arsenate on Fe3O4@SiO2 magnetic nanoparticles under mild conditions, and characterized by transmission electron microscope (TEM), Fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometer (VSM). The prepared ZrAs-Fe3O4@SiO2 was applied for the selective enrichment of phosphopeptides from the digestion mixture of phosphoproteins and bovine serum albumin (BSA). Our results demonstrated that the ZrAs-Fe3O4@SiO2 magnetic nanoparticles possess higher selectivity for phosphopeptides and better capture capability towards multiply-phosphorylated peptides than commercial zirconium dioxide (ZrO2), which has been widely employed for the enrichment of phosphopeptides. In addition, endogenous phosphopeptides from human serum can be effectively captured by ZrAs-Fe3O4@SiO2 magnetic nanoparticles. It is the first report, to the best of our knowledge, in which the zirconium arsenate-modified magnetic nanoparticles were successfully applied to the enrichment of phosphopeptides, which offers the potential application of this new material in phosphoproteomics study.