Preparation of Polyethylenimine Modified Nickel Ferrite-Graphene Oxide Material and Its Application in Enrichment of Phosphopeptides

The NiFe2O4 - graphene oxide nanocomposite modified with polyethylenimine (GO@PEI - NiFe2O4 ) was prepared to purify and enrich phosphopeptides from biosamples. The Ni (2+) and Fe 3+ ions on its surface could coordinate with phosphate groups and then selectively adsorb phosphopeptides. PEI was conducive to the above combination due to its high hydrophilicity. The material showed good magnetic response properties and could be rapidly separated from samples with the aid of magnet. With tryptic digest of beta - casein as sample, the enrichment property of the material to phosphopeptides was studied, which was compared with the results of GO@NiFe2O4 , revealing the adsorption mechanism of GO@PEI - NiFe2O4 . The static and dynamic binding properties of GO@PEI - NiFe(2)O(4 )were investigated using pTyr as a representative phosphopeptide, and the adsorption capacity was 36.2 mu g/mg. The results showed that the material could remove the interference of nonphosphopeptides and effectively enrich phosphopeptides in complex matrix. After enrichment by GO@PEI - NiFe2O4 , 1535 phosphopeptides were identified from the tryptic digest of rat liver by mass spectrum and the enrichment effect of GO@PEI -NiFe2O4 greatly outperformed commercial Fe 3+ - IMAC kits. This work provided an efficient material for the enrichment of phosphopeptides, showing potential applications in phosphoproteomics research.