Chemical synthesis makes it possible to use any amino acid, not only those dictated by the genetic code. That opens up a toolbox for design. Some common examples in research peptides:
- Aib (aminoisobutyric acid): it has two methyls on the alpha carbon, favours the helix and blocks cleavage by DPP-4. Semaglutide uses it at position 2.
- Norleucine (Nle): almost identical to methionine but without sulphur, so it does not oxidise. It appears in melanocortin analogues.
- Dmt (2′,6′-dimethyltyrosine): a modified tyrosine found in SS-31.
- Ornithine, sarcosine or N-methylated amino acids, which alter flexibility or resistance to proteases.
D-amino acids, the mirror forms of natural ones, are another very widely used category.
Why it matters in peptide research
When an analogue's sequence includes unusual abbreviations (Aib, Nle, Dmt), they almost always signal a specific design decision: protection against an enzyme or against oxidation, or stabilisation of the active shape.
Related terms
Learn it in depth at the Peptide University
Related catalogue compounds
Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).