Isotope-Labeled Amino Acids

Natural amino acids consist of four key elements: 1H (hydrogen), 12C (carbon), 14N (nitrogen), and 16O (oxygen). When one or more atoms are replaced by isotopes or “heavy” atoms (such as 1H by 2H (D), 12C by 13C, 14N by 15N, and 16O by 17O or 18O), the resulting amino acids are called isotope-labeled amino acids. While most isotope-labeled amino acids and their natural counterparts share identical structures and properties, their presence and levels can be detected and measured by analytical methods such as mass spectrometry (MS) and nuclear magnetic resonance (NMR), with MS being the preferred method. Isotope-labeled amino acids have become an increasingly important tool for proteomic research.