Magnetic titanium dioxide nanomaterial modified with hydrophilic dicarboxylic ligand for effective enrichment and separation of phosphopeptides and glycopeptides.

A dual functionalized magnetic nanomaterial was fabricated by combining the magnetic core, titania shell, and hydrophilic molecules (denoted as Fe3O4@TiO2-IDA). Based on the mechanism of metal oxide affinity chromatography and hydrophilic interaction liquid chromatography, the sorbent shows excellent one-step separation capacity for both glycopeptides and phosphopeptides. For phosphopeptide enrichment, Fe3O4@TiO2-IDA exhibits high sensitivity and selectivity. The concentration of β-casein in the digests can be as low as 0.0125 ng μL-1; the mass ratio of β-casein and BSA digest can reach 1:800. For glycopeptide enrichment, Fe3O4@TiO2-IDA also exhibits good performance. The concentration of horseradish peroxidase (HRP) in the digested sample can be as low as 0.04 ng μL-1; the mass ratio of HRP and BSA digest can reach 1:100. Following the one-step enrichment, elution, and nano LC-MS/MS analysis, 550 unique phosphopeptides and 330 glycopeptides were identified from 100 μg mouse brain sample through a single run of LC-MS/MS. Graphical abstract Multipurpose Fe3O4@TiO2-IDA nanomaterials are employed in simultaneous enrichment and separation of glycopeptides and phosphopeptides.