Preparation of Er-Nd-TiO2 nanocomposite for the highly selective enrichment of phosphotyrosine peptides

Abstract

The enrichment method of trace phosphotyrosine(pTyr) peptides from complex biological samples is of great concern in pTyr proteomics studies by mass spectrometry. In this study, Er-Nd-TiO2 (Er3+/Nd3+ co-doped TiO2) was designed and successfully synthesized by sol–gel method. The Er-Nd-TiO2 possess high sensitivity (detection limit of 1 × 10−10 M), high selectivity at a low molar ratio of 1:1000:1000 (pTyr peptides: phosphopeptides: non-phosphopeptides), less preferences, and good reusability (8 cycles). The high enrichment efficiency and specificity for phosphotyrosine peptides are ascribed to the synergistic effect of doped Er and Nd, which not only inhibit the growth of TiO2 nanocrystals inducing a high specific surface area but also have strong affinity and coordination ability toward the phosphate groups of peptides. Moreover, the cation–π interactions between metal cation Er, Nd, Ti and the phenyl ring in an aromatic side chain of tyrosine residue further enhances the specific enrichment of phosphotyrosine peptides by Er-Nd-TiO2. Compared with commercial TiO2, the nanomaterial Er-Nd-TiO2 had better specific adsorption of p-Tyr peptides and could be applied to the enrichment of p-Tyr peptides in complex samples.