Isotope Labeled Peptides

Isotope labeled or heavy amino acids are derived from natural amino acids by substitution of atoms with respective heavy isotopes. The most frequent substitutions of non-radioactive amino acids are 12C by 13C, of 14N by 15N, and of 1H by 2H (deuterium).

Stable isotopically labeled peptides (SIL) containing stable isotope labeled amino acids share the same physiochemical properties and (apart from a few exceptions) the same chemical reactivity with their non-labeled counterparts. However, under certain conditions labeled and unlabeled peptides behave differently. This is the basis for the use of stable isotope labeled peptides in a variety of applications, e.g.

  • Reference material for mass spectrometry experiments (proteomics)
  • NMR studies (e.g. solution structure determination)
  • Reference material for pharmacokinetic analyses
  • Metabolite identification

At JPT, we annually synthesize thousands of peptides with stable isotope labels. The table below lists the most common stable isotopically labeled amino acids. Other labeled amino acids are available upon request.

Amino Acid One-Letter Code Isotope Mass Difference
Alanine A U- 13C3, U-15N +4 Da
Arginine R U- 13C6, U-15N4 +10 Da
Leucine L U- 13C6, U-15N +7 Da
Lysine K U- 13C6, U-15N2 +8 Da
Phenylalanine F U- 13C9, U-15N +10 Da
Proline P U- 13C5, U-15N +6 Da
Valine V U- 13C5, U-15N +6 Da

Please also have a look at our economic SpikeTides™ proteotypic peptides

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