Phosphopeptide separation using radially aligned titania nanotubes on titanium wire.

Phosphoproteomic analysis offers a unique view of cellular function and regulation in biological systems by providing global measures of a key cellular regulator in the form of protein phosphorylation. Understanding the phosphorylation changes between normal and diseased cells or tissues offers a window into the mechanism of disease and thus potential targets for therapeutic intervention. A key step in these studies is the enrichment of phosphorylated peptides that are typically separated and analyzed by using liquid chromatography mass spectrometry. The mesoporous titania beads/particles (e.g., Titansphere TiO2 beads from GL Sciences Inc., Japan) that are widely used for phosphopeptide enrichment are expensive and offer very limited opportunities for further performance improvement. Titiania nanotube arrays have shown promising characteristics for phosphopeptide separation. Here we report a proof-of-concept study to evaluate the efficacy of nanotubes on Ti-wire for phosphoproteomics research. We used titania nanotubes radially grown on titanium wires as well as the commercial beads to separate phosphopeptides generated from mouse liver complex tissue extracts. Our studies revealed that the nanotubes on metal wire provide comparable efficacy for enrichment of phophopeptides and offer an ease of use advantage versus mesoporous beads, thus having the potential to become a low cost and more practical material/methodology for phosphopeptide enrichment in biological studies.