title: Efficient enrichment of phosphopeptides by magnetic TiO₂-coated carbon-encapsulated iron nanoparticles.
abstract: Titanium dioxide (TiO₂) has been widely used for phosphopeptide enrichment. Several approaches have been reported to produce magnetic TiO₂ affinity probes. In this report, we present a facile approach to immobilize TiO₂ onto poly(acrylic acid)-functionalized magnetic carbon-encapsulated iron nanoparticles as affinity probes for efficient enrichment of phosphopeptides. By using the new magnetic TiO₂ affinity probes, denoted as TiO₂-coated Fe@CNPs, rapid and effective MALDI-TOF MS profiling of phosphopeptides was demonstrated in different model systems such as tryptic digests of β-casein, and complex β-casein/BSA mixture. The TiO₂-coated Fe@CNPs out-performed the commercial TiO₂-coated magnetic beads for detection of phosphopeptides from tryptic digests of β-casein/BSA mixture with a molar ratio of 1:100. The new TiO₂-coated magnetic probes were also proven to be applicable for real life samples. The magnetic TiO₂-coated Fe@CNPs were employed to selectively isolate phosphopeptides from tryptic digests of HeLa cell lysates and out-performed the commercial magnetic TiO₂ beads in the number of identified phosphopeptides and phosphorylation sites. In a 200-μg equivalent of HeLa cell lysates, we identified 1415 unique phosphopeptides and 1093 phosphorylation sites, indicating the good performance of the new approach.
authors.affiliation: Department of Applied Chemistry, National Chi Nan University, Puli, Nantou, Taiwan.
authors.forename: Yi Y
authors.initials: YY
authors.lastname: Zeng
authors.forename: Huang-Juo
authors.initials: HJ
authors.lastname: Chen
authors.forename: Kai J
authors.initials: KJ
authors.lastname: Shiau
authors.forename: Shain-Un
authors.initials: SU
authors.lastname: Hung
authors.forename: Yi-Sheng
authors.initials: YS
authors.lastname: Wang
authors.forename: Chih-Che
authors.initials: CC
authors.lastname: Wu
mesh_terms: D002846:Chromatography, Affinity / Q000379:methods; D006367:HeLa Cells; D006801:Humans; D007501:Iron / Q000737:chemistry; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D010748:Phosphopeptides / Q000737:chemistry*; D010766:Phosphorylation; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D014025:Titanium / Q000737:chemistry*
chemical_list: D058185:Magnetite Nanoparticles; D010748:Phosphopeptides; C009495:titanium dioxide; D014025:Titanium; D007501:Iron