Design of two-dimensional molybdenum trioxide-immobilized magnetic graphite nitride nanocomposites with multiple affinity sites for phosphopeptide enrichment.

Here, two-dimensional magnetic graphite nitride nanosheets were synthesized, over which molybdenum trioxide was distributed evenly. The magnetic nanocomposite served as an enrichment platform for phosphopeptides based on metal oxide affinity chromatography and anion-exchange chromatography. Owing to the abundant affinity sites, positive electricity, and large surface area, the nanocomposite had high selectivity (α-casein/ß-casein/bovine serum albumin, 1:1:5000), sensitivity (0.1 fmol), quantitative recovery (91.3%), and good recyclability (10 cycles). The nanocomposite also showed good enrichment performance for phosphopeptides from non-fat milk, human serum, saliva, and A549 cell lysate. The results demonstrated the value of this material in phosphorylated proteomics.