Rapid enrichment and determination of phosphopeptides using bacterial magnetic particles via both strong and weak interactions

Bacterial magnetic nanoparticles (BMP) are used in rapid enrichment and determination of phosphorylated peptides. Fe3+ and Zr4+ can be easily immobilized on the surface of BMP without any other modification, and the metal ion immobilized BMP can enrich phosphopeptides rapidly through strong coordination bonding. It is found that the Zr4+-immobilized BMP can enrich the multiphosphorylated peptides while Fe3+-immobilized BMP preferred the singly phosphorylated peptides. Fe3+-immobilized BMP could detect phosphorylated peptides under lower concentration than that of Zr4+ owing to the larger amount of Fe3+ on BMPs. Besides, BMP itself can enrich one kind of phosphorylated peptide from alpha-casein digest directly through weak interactions between BMP and phosphorylated peptides.