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. Fe(3+) and Zr(4+) 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 Zr(4+)-immobilized BMP can enrich the multiphosphorylated peptides while Fe(3+)-immobilized BMP preferred the singly phosphorylated peptides. Fe(3+)-immobilized BMP could detect phosphorylated peptides under lower concentration than that of Zr(4+) owing to the larger amount of Fe(3+) 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.