Biosynthesis and chemical synthesis are the main methods to synthesize stable isotope labeled peptides The biosynthesis method is to mark the target site in the physiological metabolism of animals, plants, enzymes or microorganisms Chemical synthesis method according to the principle of conventional chemical reaction, the labeled target compound is prepared by chemical synthesis method by using stable isotope labeled conventional reagent instead of non labeled basic reagent (N-Fmoc-7-methyl-L-tryptophan)

With the development of mass spectrometry, The quantitative detection method based on mass spectrometry has gradually become the mainstream of the quantitative relationship of biomolecules ,Among them, isotope dilution mass spectrometry is widely used in the quantitative detection of biomolecules by taking advantage of its quantitative advantages. Isotope dilution mass spectrometry usually uses reagents rich in certain heavy isotopes such as 2H, 13C, 15N and 18O to label the internal standard of the peptide to be measured. Because there is a difference in the mass number of the internal standard peptide and the peptide to be measured, CBZ-OSu the spectrum shows two peaks with different mass to charge ratios when the mass spectrometry is used for testing. The spacing between the two peaks is determined by The target is determined by the number of labeled heavy isotopes.

Because the stable isotope labeled internal standard compounds used in isotope dilution mass spectrometry are almost identical to the endogenous biomolecular structures and physical and chemical properties to be detected. The behavior of chromatography and mass spectrometry is the same. Therefore, it can effectively eliminate the influence of matrix Fmoc-OSu interference and sample pretreatment process on the detection recovery. It is an accurate and reliable quantitative method. Isotope dilution mass spectrometry based on biological sample detection mostly adopts the method of liquid chromatography and mass spectrometry. This method fully combines the high selectivity of high performance liquid chromatography and the high sensitivity of mass spectrometry. It does not need derivatization when determining stable isotope labeled peptides, and the detection process is simple. However, it is difficult to synthesize stable isotope labeled peptide internal standard compounds, which limits its application