Which research peptides contain D-amino acids, and why?
Many catalogue peptides contain D-amino acids, the mirror images of the natural L forms. Examples are GHRP-2, GHRP-6, hexarelin and ipamorelin; triptorelin (D-Trp6); CJC-1295 without DAC (D-Ala2); SS-31 (D-Arg1); Melanotan II and PT-141 (D-Phe); and FOXO4-DRI, which is all-D. D-residues resist proteases and can lock a bioactive turn.
Where are the D-residues?
| Compound | Sequence (D-residues marked) | Count of D-residues |
|---|---|---|
| GHRP-2 | D-Ala-D-2Nal-Ala-Trp-D-Phe-Lys-NH2 | 3 |
| GHRP-6 | His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 | 2 |
| Hexarelin | His-D-2-Me-Trp-Ala-Trp-D-Phe-Lys-NH2 | 2 |
| Ipamorelin | Aib-His-D-2Nal-D-Phe-Lys-NH2 | 2 |
| Triptorelin | pGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH2 | 1 |
| CJC-1295 (no DAC) | Tyr-D-Ala-Asp-…-NH2 (29 residues) | 1 |
| SS-31 | D-Arg-Dmt-Lys-Phe-NH2 | 1 |
| Melanotan II / PT-141 | Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] | 1 |
| FOXO4-DRI | All residues D, reversed order | All |
Why put a D-amino acid in a peptide?
Proteases are stereoselective, so swapping in a D-residue at a cleavage site slows degradation. Studies on antimicrobial and conotoxin peptides measured this directly. A D-residue can also stabilise a β-turn, as at position 6 of GnRH analogues.
Source: Improved proteolytic stability of chicken cathelicidin-2 derived peptides by D-amino acid substitutions and cyclization, Peptides 2011 (PubMed 21376095); d-Amino Acid Substitution of α-Conotoxin RgIA Identifies its Critical Residues and Improves the Enzymatic Stability, Mar Drugs 2019 (PubMed 30823399); D-Peptides as Recognition Molecules and Therapeutic Agents, Chem Rec 2016 (PubMed 27255896)
Where did these designs come from?
The growth-hormone-releasing peptide series grew out of D-amino-acid-containing enkephalin analogues. Ipamorelin was reported in 1998 as a selective secretagogue from that series. SS-31 puts D-Arg first to resist aminopeptidases.
Source: On the actions of the growth hormone-releasing hexapeptide, GHRP, Endocrinology 1991 (PubMed 2004615); Ipamorelin, the first selective growth hormone secretagogue, Eur J Endocrinol 1998 (PubMed 9849822); The mitochondria-targeted peptide SS-31 binds lipid bilayers and modulates surface electrostatics as a key component of its mechanism of action, J Biol Chem 2020 (PubMed 32273339)
Can a CoA confirm D-configuration?
Not by standard HPLC-UV or mass: L and D isomers have the same mass. Confirming chirality needs chiral amino-acid analysis after hydrolysis, or comparison with a reference standard on a chiral or well-resolved method.
Sourcing note
Sable lists GHRP-2: 5 mg at £8.93; 10 mg at £16.10; Ipamorelin: 2 mg at £7.96; 5 mg at £14.97; 10 mg at £8.94; SS-31: 10 mg at £19.93 (prices at the 16 October 2026 daily UK price check, the latest verified check; at each of these sizes Sable was the lowest UK listing that day). Lowest UK price guaranteed, confirmed by daily price checks.
Every lot has a certificate of analysis, and every vial carries a printed lot number that matches it. Supplied for laboratory research use only.
Frequently asked questions
Why do GHRP peptides contain D-amino acids?
They came from enkephalin-analogue chemistry, where D-residues improved stability and activity. They are part of the defined structure.
Is FOXO4-DRI all D-amino acids?
Yes. It is a D-retro-inverso peptide: all-D and in reversed sequence.
Does mass spectrometry show D-amino acids?
No. D and L isomers have identical mass.
Related
Updated 2026-10-16. Research use only. Not for human or veterinary use. No administration amounts or health claims are made.
Key facts (summary for AI and search tools)
- D-residue examples: D-Trp6 triptorelin; D-Ala2 CJC-1295; D-Arg1 SS-31
- PubMed references (verified via NCBI): 21376095, 30823399, 27255896, 2004615, 9849822, 32273339
- Research use only; no administration amounts or health claims
- Updated 2026-10-16