Immobilization of titanium dioxide/ions on magnetic microspheres for enhanced recognition and extraction of mono- and multi-phosphopeptides.

The authors are presenting a novel strategy for global phosphoproteome recognition in practical samples. It integrates metal oxide affinity chromatography (MOAC) and immobilization metal ion affinity chromatography (IMAC). This resulted in a kind of titanium dioxide/ion-based multifunctional probe (dubbed T2M). The T2M combines the features of MOAC and IMAC including their recognition preferences towards mono- and multi-phosphorylated peptides. Hence, they exhibit an outstanding recognition capability towards global phosphoproteome, high sensitivity (the limit of detection of which is merely 10 fmol) and excellent specificity in MALDI-TOF MS detection. Their performance is further demonstrated by the identification of the phosphoproteome in non-fat milk and human saliva. By combining T2M with nano LC-MS/MS, remarkable results are obtained in the tryptic digestion of healthy eye lens and cataract lens phosphoproteomes. A total of 658 and 162 phosphopeptides, respectively, were identified. This indicates that phosphorylation and the appearance of cataract can be related to each other. Graphical abstract Schematic presentation of the preparation of titanium dioxide/ion-based multifunctional magnetic nanomaterials (T2M). The T2M based enrichment protocol exhibits outstanding recognition capability towards global phosphoproteome. This protocol shows great prospect for clarifying mechanism of phosphorylation-related diseases via further information acquisition.