Establishment and Optimization of Protein Labeling Based on Rare Earth Metal Chelated Tags

A strategy for protein labeling based on rare earth metal chelating as an elemental tag was established. Several influencing factors were examined to ensure the completeness and efficiency of the reaction. The first step of acylation reaction was performed in 50 mM TEAB buffer (pH 7.5) for 30 min at room temperature, and the molar ratio of DTPA with peptide was 100. The second step of rare earth metal chelating was performed in 100 mM ammonium acetate buffer (pH 6) for 1 h at 37 °C, and the molar ratio of rare earth metals with DTPA was 4. The chelating efficiency of different rare earth metal was compared. The results showed that the metal chelating of Lu with the minimum ionic radius had the maximum efficiency. The labeling strategy was successfully applied in peptide mixture.