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Stable isotope labeled peptides (SIL peptides), also known as heavy peptides, are chemically synthesized peptides with the native sequence, but some of the constituent amino acids are replaced by the stable isotope labeled amino acids, such as 12C by 13C, 14N by 15N, and 1H by 2H. Stable isotope labeled peptides are chemically and physically indistinguishable from their endogenous counterparts with respect to retention time, ionization efficiency and fragmentation mechanism. They only differ by mass. These properties make the stable isotope labeled peptides could be widely applied in quantification analysis (e.g. ICAT, iTRAQ and AQUA), the nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) and reference materials for pharmacokinetic analyses and metabolite identification. Other applications include the protein structure analysis, protein expression monitoring, protein cross-linking analysis, quantitative proteomics, biomarker discovery, cell signal profiling, and pathway validation.
Fig.1 Overview of quantification approaches in LC-MS based proteomic experiments. 
As a world-leading peptide manufacturing organization, Creative Peptides possesses extensive expertise and years of experience which is able to provide customized stable isotope labeled peptides synthesizing service to customer worldwide. All stable isotope labeled peptides are synthesized using the latest Fmoc solid-phase peptide technology and performed mass spectrometric analysis and stringent analytical HPLC to establish the final purity, to assure that our customers receive the highest quality peptides. Creative Peptides is a reliable partner that can work with you to accelerate the speed to achieve your research goals.