Establishment and Optimization of Stable Isotope 18O-labeling Strategy for Quantitative Proteomics Research

A method for relative quantitation of complex protein mixtures was developed using oxygen-18 labeling and mass spectrometric analysis. Some major influencing factors, such as pH, temperature, and reaction time, were evaluated and optimized. The experimental results showed that a desirable labeling could be realized with tryptic catalysis in a pH 5.0 buffer composed of K2HPO4/KH2PO4 for 16 hours at 37°C. Under these conditions, the efficiency of 18O-labeling for the quantitative analysis of tryptic peptides could be up to 100%. The investigations on the dynamic range and quantitative accuracy were performed by observing and calculating the ratio of the peak intensity in mass spectra with several 16O/18O peptide couples from tryptic digestion of myoglobin, and a favorable linear correlation with 0.99 of r value and 18.4% of deviation in a 1:10 concentration range were obtained, which indicated that the protocol developed in this study is reliable and stable.