Efficient Enrichment of Global Phosphopeptides Using Magnetic Tannic Acid – Titanium(IV)/Zirconium(IV) Functionalized Spheres as a Novel Sorbent for Immobilized Metal Ion Affinity Chromatography (IMAC)

Inspired by the enrichment preferences of metal ions for phosphopeptides, a layered assembly method was adopted to introduce hydrophilic polyhydroxy ligands tannic acid (TA) to prepare magnetic bimetal ion-functionalized nanomaterials denoted by Fe3O4@TA@Ti4+/Zr4+ to provide the comprehensive enrichment of phosphopeptides. Benefiting from the excellent ion immobilization ability and unbiasedness for phosphopeptide enrichment, Fe3O4@TA@Ti4+/Zr4+ shows excellent properties for the enrichment and identification of global phosphopeptides. The results show that the material possesses high efficiency, outstanding selectivity (the maximum molar ratio β-casein to bovine serum albumin is 1:1000), a low detection limit of 0.4 fmol/μL, and the ability to be recycled at least 10 times. In addition, excellent performance was also demonstrated in the analysis of skimmed milk and human saliva: 13 and 31 phosphopeptides were successfully captured. The results demonstrate that the material has high potential for practical application in phosphoproteomics.