Preparation of Bi 0.15 Fe 0.15 TiO 2 Nanocomposites for the Highly Selective Enrichment of Phosphopeptides.

Novel Bi _0.15 Fe _0.15 TiO ₂ nanocomposites (B _0.15 F _0.15 TNs) were synthesized for the first time by a modified sol-gel technology and successfully applied to selective extraction and enrichment of phosphopeptides from digested protein mixture solutions and real samples (tissue protein extract from human liver). The codoping of Bi and Fe into TiO ₂ results in a significant enhancement in both the enrichment efficiency and selectivity. Compared with the commercial available TiO ₂ extractant, the proposed B _0.15 F _0.15 TNs possess a lower detection limit (2 × 10 ^-9 M) and higher selectivity at a low weight ratio of 1:1200 (phosphopeptides/nonphosphopeptides). Additionally, a total of 223 phosphorylation sites were identified from the human liver lysate after enrichment by the B _0.15 F _0.15 TNs. In addition, the synthesis of B _0.15 F _0.15 TNs is quite easy, of high yield, and inexpensive.