Ultrathin-yttrium phosphate-shelled polyacrylate-ferriferrous oxide magnetic microspheres for rapid and selective enrichment of phosphopeptides

Rapid and selective enrichment of phosphopeptides from complex biological samples is essential and challenging in phosphorylated proteomics. We present the direct growth of the ultrathin YPO 4 shell on the surface of polyacrylate capped secondary Fe 3 O 4 microspheres (PA-Fe 3 O 4 @YPO 4 ) for the rapid and selective trapping phosphopeptides from complex samples. The prepared PA-Fe 3 O 4 @YPO 4 could be rapidly harvested in the presence of an applied magnetic field and easily re-dispersed in solutions after removing the external magnet. The ultrathin YPO 4 shell on super-hydrophilic PA-Fe 3 O 4 has the advantages of fast adsorption/desorption dynamics and low non-specific adsorption, thus trapping of phosphopeptides from the tryptic digests mixture of β-casein/BSA with molar ratio of 1/300 is achieved in 20   s adsorption/desorption time. Two phosphopeptides can still be detected with a signal to noise ratio (S/N) over 3 when the amount of β-casein was as low as 8   fmol.