Ball-and-stick model of a pentapeptide with two aromatic rings seated in a translucent receptor pocket, representing ipamorelin structure

Ipamorelin Peptide: Pentapeptide Structure and Stability

Key takeaways

Ipamorelin peptide is the pentapeptide Aib-His-D-2-Nal-D-Phe-Lys-NH2: CAS 170851-70-4, C38H49N9O5, 711.9 g/mol.
Three non-proteinogenic residues (Aib, D-2-Nal, D-Phe) and a C-terminal amide leave no protease cleavage site.
No Met, Cys, Asn or Gln, so oxidation, disulfide and deamidation routes do not apply; stocks are limited by adsorption.
4 mg vial in 1 mL = 4 mg/mL = 5.62 mM; identity by MS at [M+H]+ about 712.9.
For in vitro research use only.

Ipamorelin peptide is a synthetic pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH₂ (CAS 170851-70-4, C₃₈H₄₉N₉O₅, 711.9 g/mol, PubChem CID 9831659), in which three of the five residues are non-proteinogenic and the C-terminus is an amide; those features make it unusually resistant to proteolysis and give it its selectivity for the growth-hormone secretagogue receptor GHS-R1a. This profile is about the molecule itself: what each residue contributes, why the sequence is stable in solution, how it is stored and reconstituted, and how its identity is confirmed. Receptor selectivity and assay design are covered in the linked guides rather than repeated here.

What is the ipamorelin sequence?

Position	Residue	Type	Contribution
1	Aib (2-aminoisobutyric acid)	Non-proteinogenic, achiral	Alpha,alpha-disubstituted; blocks aminopeptidases and restricts backbone conformation
2	His	Proteinogenic	Imidazole side chain, shared with other GHRPs
3	D-2-Nal (D-3-(2-naphthyl)alanine)	Non-proteinogenic, D-configured	Large aromatic group that fills the hydrophobic receptor pocket; D-stereochemistry resists proteases
4	D-Phe	D-configured	Second aromatic contact; D-stereochemistry resists proteases
5	Lys-NH₂	Proteinogenic, C-amide	Basic side chain; the amide removes the C-terminal negative charge and blocks carboxypeptidases

The pattern of a basic residue, an aromatic pair and a capped terminus is the pharmacophore shared across the growth-hormone-releasing-peptide (GHRP) family; ipamorelin is the shortest member in the catalog. Its place among the GH secretagogues is set out in growth hormone secretagogues: receptor pathways and in vitro assays.

Why is ipamorelin so stable in solution?

Proteases recognize L-amino acids in a peptide backbone. With Aib at the N-terminus and two consecutive D-residues in the middle, there is no standard cleavage site in the sequence, and the C-terminal amide removes the carboxypeptidase substrate. The molecule also has no methionine, cysteine, asparagine or glutamine, so the common chemical degradation routes (oxidation, disulfide scrambling, deamidation) do not apply. The practical consequence is that ipamorelin stock solutions are limited by adsorption and microbial growth rather than by chemical breakdown, which is unusual for a peptide this small.

Physical properties and solubility

At 711.9 g/mol ipamorelin is at the small-molecule end of the peptide range. It carries two basic groups (the N-terminal amine and the lysine side chain) and the histidine imidazole, so it is water-soluble at neutral and acidic pH and is supplied as a white lyophilized powder. The two naphthyl and phenyl rings make it moderately hydrophobic, which is why it adsorbs to untreated polystyrene at low concentrations; use low-binding plastic or a small amount of carrier protein for sub-micromolar working solutions.

Storage and reconstitution

Keep the powder cold, dry and dark. The Ipamorelin vial is listed at 4 mg; reconstituting it in 1 mL of reconstitution solution gives 4 mg/mL, a 5.62 mM stock; 2 mL gives 2 mg/mL (2.81 mM) and 4 mL gives 1 mg/mL (1.40 mM). Aliquot and freeze. In the Ipamorelin/CJC-1295 (no DAC) blend the ipamorelin mass is 5 mg; that vial's math is in sourcing a two-component blend.

How is identity confirmed?

The mass spectrum should show [M+H]⁺ at about 712.9 and [M+2H]²⁺ at about 356.9. Because the sequence contains D-residues, the identity question also includes stereochemistry: an all-L diastereomer has the same mass. Chiral amino-acid analysis or a comparison of HPLC retention against a reference standard is the way to confirm the D-configuration if it matters to the experiment. The COA conventions are explained in sourcing ipamorelin as a research material.

Where does ipamorelin fit in receptor research?

It is the catalog's selective GHS-R1a agonist, used alone in calcium-flux and reporter assays and paired with the GHRH analog CJC-1295 no DAC for dual-receptor work. Selectivity data are discussed in ipamorelin and GHS-receptor selectivity, the signaling pathway in GHS-receptor signaling in vitro, and the pairing in the CJC-1295 + ipamorelin blend profile.

Related research guides

Research-use note

All materials discussed are supplied for in vitro laboratory research use only, and are not for human or animal use.

Frequently asked questions

What is the ipamorelin peptide?

A synthetic pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2 (CAS 170851-70-4, C38H49N9O5, 711.9 g/mol), with three non-proteinogenic residues and a C-terminal amide that make it protease-resistant and selective for the GHS-R1a receptor; supplied as lyophilized powder for in vitro research. View Ipamorelin

Why is ipamorelin stable in solution?

Aib at the N-terminus, two consecutive D-residues and a C-terminal amide remove all standard protease sites, and the sequence has no oxidation- or deamidation-prone residues.

What concentration does a 4 mg vial give in 1 mL?

4 mg/mL, which is 5.62 mM at 711.9 g/mol; 2 mL gives 2.81 mM and 4 mL gives 1.40 mM.

How is ipamorelin identity confirmed?

By mass spectrometry, [M+H]+ about 712.9 and [M+2H]2+ about 356.9, with chiral analysis or reference-standard HPLC if the D-configuration must be confirmed. MS identity guide

Is ipamorelin for human or animal use?

No. It is supplied for in vitro laboratory research use only.