Synthesis and Characterization of Silica-zirconia Composite for the Enrichment of Phosphopeptides

Silica-zirconia composite (SiO2-ZrO2) was synthesized by sol-gel method, and its physical-chemical properties were investigated using several techniques. The enrichment capacity of silica-zirconia composite and zirconia was compared using tryptic digest of a-casein as probe. The results showed that the selectivity of SiO2-ZrO2 was better than that of ZrO2 when the pH of the loading solution was below 2. The enrichment capacity of SiO2-ZrO2 for multiple phosphorylated peptides was better than that of ZrO2. In combination with matrix-assisted laser desorption ionization-time of flight (MALDI-TOF)-based peptide mass finger printing technique, SiO2-ZrO2 was used to enrich the phosphopeptides from nonfat milk successfully.