Magnetic resin composites for the enrichment of proteins, peptides and phosphopeptides

There is growing interest in the development of materials for enriching proteins and phosphoproteins from complex sample matrices for mass spectrometric analysis. Herein, we designed and synthesized two types of magnetic resin composites, i.e., MTS9200@Fe₃O₄ and FPA90CL@Fe₃O₄, and assessed their applications as adsorbents for enriching proteins, peptides and phosphopeptides. With the combination of Fe³⁺-IMAC interaction (MTS9200) or electrostatic attraction (FPA90CL) of resins and the adsorption of Fe₃O₄, the prepared composites exhibited higher capacities for adsorbing a protein (bovine serum albumin, at 195.71 and 135.03 mg g^-1 for MTS9200@Fe₃O₄ and FPA90CL@Fe₃O₄, respectively) than MTS9200, FPA90CL and Fe₃O₄. In addition, due to the contributions of the hydrophobic skeleton of resins and Fe₃O₄, the magnetic resin composites allowed for efficient enrichment of peptides. Moreover, through Fe³⁺-IMAC interaction or electrostatic attraction of resins and Fe-O MOAC interaction of Fe₃O₄ with phosphate groups, phosphopeptides could also be captured. Furthermore, we employed the prepared composites for enriching proteins and phosphopeptides from human serum, where 466 and 506 proteins, and 434 and 356 phosphorylation sites, were detected from human serum after being processed with FPA90CL@Fe₃O₄ and MTS9200@Fe₃O₄, respectively. Together, our work revealed the great potential of magnetic resin composites as enrichment materials for proteomics and phosphoproteomics analysis.