A metal oxide affinity probe derived from MIL-125 for selective enrichment of endogenous phosphopeptides.

Highly effective enrichment of endogenous phosphopeptides from complex biological samples is an essential and crucial theme in the analysis of phosphopeptidomics. Herein, an ordered mesoporous TiO2/C composite (denoted as Ti-MCM) was prepared by the pyrolysis of MIL-125 under a N2 atmosphere. The obtained Ti-MCM possesses a high specific surface area (165 m2 g-1), a uniform pore size (3.75 nm), and a large amount of Ti (46%). By utilizing the selective chelation between Ti-MCM and phosphopeptides, 25 phosphopeptides were detected in α-casein digest after enrichment. The material shows good selectivity even in the presence of 2000-fold excess of interference peptides. It was also used to enrich endogenous phosphopeptides from the complex samples of human serum and saliva and showed a good performance.