Specific recognition of tyrosine-phosphorylated peptides by epitope imprinting of phenylphosphonic acid

Protein phosphorylation on tyrosine residues is an important cell signaling mechanism that regulates embryo development, cell growth, differentiation and migration. Here, we developed an epitope imprinting approach to selectively enrich tyrosine-phosphorylated (pTyr) peptides using molecularly imprinted polymers (MIPs). An artificial receptor based on MIPs was prepared by precipitation polymerization using phenylphosphonic acid (PPA) as a template, Ti4+-immobilized ethylene glycol methacrylate phosphate as functional monomer, poly(ethylene glycol) diacrylate and N,N′-methylenebisacrylamide as crosslinkers, and deionized water as a porogen. The performance of MIPs was first evaluated by rebinding PPA, and then a competition experiment was conducted to assess the selectivity and specificity for PPA when mixed with benzoic acid, a structural analog. The imprinting factor of the MIPs was up to 2.04, compared with just 0.24 for benzoic acid. The selectivity and capacity of the MIPs for pTyr peptides from a mixture of peptides were considerably higher than that of commercial TiO2. And after six rebinding cycles, there were still 95% adsorption efficiency retained. Finally, MIPs were used for pTyr enrichment from a complex sample containing pTyr peptide and tryptic digestion of β-casein, where it demonstrated a clear preference for the pTyr peptide over ones containing phosphorylated serine.