Facile Synthesis Of Fe₃O₄@TiO₂-ZrO₂ And Its Application In The Study Of Phosphopeptide Enrichment

Phosphorylation of proteins is a frequent post-translational modification affecting a great number of fundamental cellular functions in living organisms. The analysis of protein phosphorylation is very challenging due to its highly dynamic nature and low stoichiometry.Herein, a novel type of binary-metal-oxide-coated magnetic microspheres-titanium dioxide-zirconium dioxide -coated magnetic iron oxide (Fe3O4@TiO2-ZrO2)-which were prepared and employed to selectively capture phosphopeptides from tryptic digest products of proteins is demonstrated for the first time. The synthesized materials were characterized by SEM, TEM, EDX, FTIR, XRD, BET and VSM, respectively. In order to illustrate the enrichment characteristics of the functional magnetic material, zirconium-dioxide-coated magnetic iron oxide (Fe3O4@ZrO2) and titanium-dioxide-coated magnetic iron oxide (Fe3O4@TiO2) were also synthesized and applied for the enrichment of phosphopeptides. Beta-casein was utilized as the standard protein to optimize some conditions of trapping phosphopeptides. The mixture of beta-casein and bovine serum albumin (BSA) with different proportions and defatted milk were considered as the simulation of semi-complex samples and real biological samples to evaluate the capability of trapping phosphopeptides respectively.The results revealed that Fe3O4@TiO2 and Fe3O4@ZrO2 were inclined to capture the multiply phosphorylated peptides and singly phosphorylated peptides respectively. However, both the singly and multiply phosphorylated peptides could be concentrated effectively by Fe3O4@TiO2-ZrO2.