Magnetite nanoparticles coated with mercaptosuccinic acid-modified mesoporous titania as a hydrophilic sorbent for glycopeptides and phosphopeptides prior to their quantitation by LC-MS/MS

A hydrophilic material consisting of a magnetite core coated with mercaptosuccinic acid modified mesoporous titania (denoted as Fe3O4@ mTiO2-MSA) has been fabricated. It is shown to be a viable sorbent for capturing glycopeptides and phosphopeptides. The sorbent combines the features of metal oxide-based affinity chromatography and of hydrophilic interaction liquid chromatography (HILIC) with the advantages of using mesoporous titania. The use of magnetic microspheres provides magnetic response and simplifies separation. Following elution with 10% ammonia, the peptides were submitted to LC-MS/ MS analysis. The method enabled 327 phosphopeptides and 65 glycopeptides to be identified in three isolated replicates of merely 5 mu L samples of human saliva. Among them, the phosphorylation sites and glycosylation sites were detected in 20 peptide segments.