Why is ipamorelin heavy for five residues?

Two of the five are large aromatics. D-2-naphthylalanine especially, which carries a fused two-ring system.

Can it be quantified at 280 nm?

Yes. Its aromatic residues provide a usable chromophore, unlike several other peptides in this library.

Does it need a reducing agent?

No. There is no cysteine in the sequence.

Ipamorelin Molecular Weight and Properties

The short answer

Ipamorelin is 711.9 Da for formula C38H49N9O5 across five residues, an average of about 142 Da per residue, well above the typical 110, because D-2-naphthylalanine and D-phenylalanine are both heavy aromatic residues.

Key facts

Molecular weight: 711.9 Da
Formula: C38H49N9O5
Residues: 5
Average per residue: ~142 Da
Aromatic residues: Two (D-2-Nal and D-Phe)
Basic residues: His, Lys
Cys / Met: Neither present

Why the per-residue mass is so high

The typical average is around 110 Da. Ipamorelin's 142 reflects composition: naphthylalanine carries a fused two-ring aromatic system and is among the heaviest residues used in peptide design, and phenylalanine is heavy too. Two aromatics in five residues pushes the average well up.

What the aromatics do beyond mass

They provide a strong ultraviolet chromophore, so ipamorelin can be quantified by absorbance near 280 nm, which several peptides in this library cannot. They also contribute hydrophobic surface, giving a molecule that is less freely water-soluble than the highly charged short peptides elsewhere here.

Research material referenced

CJC-1295 + Ipamorelin 5+5mg, third-party HPLC tested

Buy CJC-1295 + Ipamorelin · £36.99

Charge

Histidine and lysine give basic character, and the C-terminal amide removes the negative charge a free carboxyl would provide. Net positive at physiological pH, with the aromatic residues contributing an unusual combination of charge and hydrophobicity for a molecule this small.

What is absent

No cysteine, so no disulfide chemistry. No methionine, so no thioether oxidation and no +16 Da satellite. The engineered residues (Aib and the two D-isomers) protect against enzymatic degradation, so both the enzymatic and the common chemical routes are largely closed.

Comparison within the category

Ipamorelin at 711.9 Da and five residues sits against CJC-1295 at 3647.2 Da and 29 residues. A fivefold mass difference between two compounds routinely discussed together. When preparing solutions of both, using one molecular weight for the other is an obvious error and an easy one, given how often they appear as a pair.

Frequently asked questions

Why is ipamorelin heavy for five residues?: Two of the five are large aromatics. D-2-naphthylalanine especially, which carries a fused two-ring system.
Can it be quantified at 280 nm?: Yes. Its aromatic residues provide a usable chromophore, unlike several other peptides in this library.
Does it need a reducing agent?: No. There is no cysteine in the sequence.

Extended research context

The CJC-1295 & Ipamorelin deep dive

Deep dive: why CJC-1295 and Ipamorelin are studied together

CJC-1295 is a modified GHRH (growth-hormone-releasing hormone) analogue; Ipamorelin is a selective growth-hormone secretagogue that binds the ghrelin receptor (GHS-R1a). In pituitary-cell research models the two act on independent pathways whose downstream effect converges on GH release. CJC-1295 amplifies the endogenous GHRH signal while Ipamorelin adds a separate ghrelin-pathway stimulus. That's why supplier catalogues frequently package them together as a research reference blend.

DAC vs no-DAC: which CJC-1295 is which

'CJC-1295 with DAC' contains a Drug Affinity Complex (a Lys-maleimide moiety) that binds serum albumin and extends half-life to several days. 'CJC-1295 no-DAC' (also called Modified GRF 1-29) lacks the linker and clears in minutes. These are pharmacologically different peptides. A CoA must specify which form is in the vial; mass differs (~3,367 Da with DAC vs ~3,367 minus linker for no-DAC).

Ipamorelin's selectivity profile

Unlike earlier GHS-R agonists (e.g. GHRP-6), Ipamorelin was engineered for minimal cross-activity at cortisol- and prolactin-releasing pathways in research models. That receptor selectivity is why it is the reference secretagogue for controlled pituitary-cell studies.

Research applications

▸Pituitary-cell GH-release assays (comparator vs GHRH and hexarelin)
▸Half-life comparison studies: DAC vs no-DAC CJC-1295 forms
▸Ghrelin-receptor binding assays for Ipamorelin analogue development
▸Analytical HPLC method development for lipidated GHRH analogues
▸Stability testing under refrigerated storage

Handling checklist

✓Store lyophilised at −20 °C long-term
✓Reconstitute in bacteriostatic water; both peptides dissolve readily
✓Aliquot immediately, refrigerate at 2–8 °C, use within 28 days
✓Confirm salt form and DAC/no-DAC status on CoA before starting a study
✓Do not use for human administration (research reference only)

Common research-handling mistakes

Learnt from thousands of researcher orders across our UK labs.

✗ Confusing DAC and no-DAC CJC-1295

Fix: Check the CoA. The two have very different pharmacokinetics.

✗ Assuming Ipamorelin acts on GHRH receptors

Fix: It binds the ghrelin receptor (GHS-R1a), a separate pathway from CJC-1295.

✗ Storing reconstituted solution at room temperature

Fix: Refrigerate 2–8 °C after reconstitution.

Continue researching

Peer-reviewed guides, comparators and matched reference materials.

Primary sources & clinical trials

Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.

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Ipamorelin Molecular Weight and Physical Properties