TiO2-modified fibrous core-shell mesoporous material to selectively enrich endogenous phosphopeptides with proteins exclusion prior to CE-MS analysis

As an important post-translational modification of proteins, phosphorylation plays a key role in regulating a variety of complicated biological reactions. Owing to the fact that phosphopeptides are low abundant and the ionization efficiency could be suppressed in mass spectroscopic detection, highly efficient and selective enrichment methods are essential to identify protein phosphorylation by mass spectrometry. Here, we develop novel titanium oxide coated core shell mesoporous silica (CSMS@TiO2) nanocomposites for enrichment of phosphopeptides with simultaneous exclusion of massive proteins. The CSMS@TiO2 nanocomposites have essential features, including uniform 1.0 mu m diameter, 120 nm thick shell, 7.0 nm mesopores perpendicular to the surface, large surface area of 77 m(2)/g and pore volume of 0.15 cm(3)/g, therefore can greatly improve the sensitivity for identifying phosphopeptides by capillary electrophoresis-mass spectrometry. The proposed CSMS@TiO2 nanocomposites are applied for analysis of beta-casein tryptic digest and bovine serum albumin (BSA) protein mixture, respectively. The results show that the number of phosphopeptides detected is tremendously increased by using CSMS@TiO2 nanocomposite, proving selectively enriching phosphopeptides due to the size-exclusive and specific interaction of the TiO2-modified mesopores. The enrichment of the phosphopeptides is achieved even for the digests at very low concentration of beta-casein (1 fmol/mu L). This research would open up a promising idea to utilize mesoporous materials in peptidomics analysis.

Automated summary

Phosphorylation, an important post-translational modification of proteins, plays a key role in regulating biological reactions. Due to the low abundance of phosphopeptides and limitations in ionization efficiency in mass spectroscopic detection, efficient and selective enrichment methods are crucial. The developed CSMS@TiO2 nanocomposites show promising results in enriching phosphopeptides and excluding massive proteins, enhancing sensitivity for identifying phosphopeptides.