Stable isotope-labeled amino acids have become indispensable tools in quantitative proteomics, metabolic flux analysis, NMR structural biology, and pharmacokinetic studies. Unlike radioactive tracers, stable isotopes (¹³C, ¹⁵N, ²H) are non-hazardous, do not decay, and can be detected with high precision by mass spectrometry.
In quantitative proteomics, SILAC (Stable Isotope Labeling by Amino Acids in Cell Culture) uses cell culture media supplemented with heavy isotope-labeled arginine and lysine to metabolically label the entire proteome. After combining light (control) and heavy (experimental) cell lysates, protein abundance changes are quantified by comparing isotope pair intensities in LC-MS/MS.
AQUA (absolute quantification) peptides are synthetic isotope-labeled peptides of defined concentration used as internal standards for absolute protein quantification. The labeled peptides are spiked into tryptic digests, providing an internal standard that co-elutes with the endogenous target peptide during LC-MS analysis.
In metabolic flux analysis, uniformly ¹³C-labeled amino acids are used to trace carbon flow through metabolic pathways. By measuring the isotopic enrichment of metabolite pools over time using GC-MS or LC-MS, researchers reconstruct flux rates through central carbon metabolism, amino acid biosynthesis, and related pathways.
For NMR structural biology, ¹⁵N and ¹³C/¹⁵N-labeled proteins expressed in isotopically enriched media enable multidimensional NMR experiments (HSQC, TROSY, NOESY) that would be impossible with natural abundance samples. Site-specific ²H labeling further reduces dipolar relaxation, enabling structural studies of large proteins.
SynthAxis supplies an extensive range of stable isotope-labeled amino acids including uniformly ¹³C/¹⁵N-labeled variants of all 20 proteinogenic amino acids, site-specifically labeled derivatives, and deuterium-labeled compounds — all with isotopic purity ≥99% and chemical purity ≥98%.