Mesoporous Fe2O3 microspheres: rapid and effective enrichment of phosphopeptides for MALDI-TOF MS analysis

Mesoporous Fe(2)O(3) microspheres have been successfully synthesized by the polymerization (urea and formaldehyde)-induced ferric hydroxide colloid aggregation. The urea-formaldehyde resin was removed by calcination in air. The obtained mesoporous Fe(2)O(3) materials have spherical morphology with uniform particle size of approximately 3.0 microm and porous surface with large inter-particle pores of approximately 48.0 nm. The surface area is as large as approximately 33.3 m(2)/g and the pore volume is 0.31 cm(3)/g. The mesoporous Fe(2)O(3) microspheres were used for the enrichment of phosphopeptides for the first time, in which high sensitivity, selectivity and capacity of specifically enriched phosphopeptides were achieved under a mild condition in a relative short time. After enriched from tryptic digest products of beta-casein by the novel mesoporous Fe(2)O(3) microspheres, phosphopeptides can be selectively detected with high intensity in MALDI-TOF mass spectrometry. Elimination of "shadow effect" was observed by using mesoporous Fe(2)O(3) microspheres, and the detectable limitation is 5x10(-10) M. This material is also effective for enrichment of phosphopeptides from the complex tryptic digests of commercial phosphoprotein casein, with much more phosphorylated sites (26 in 27 of total) and higher signal/noise ratio in the MALDI-TOF mass spectrometry, compared to commercial Fe(2)O(3) nanoparticles. It shows a great potential application in the field of rapid and effective isolation of phosphopeptides.