The short answer
The DAC form carries a maleimidopropionic acid linker binding covalently to cysteine-34 of serum albumin, extending half-life to days. Without it (Modified GRF (1-29)), clearance takes about thirty minutes. The two differ by 279.3 Da, and that mass is the reliable discriminator.
Key facts
- With DAC
- 3647.2 Da, CID 91971820
- Without DAC
- 3367.9 Da, CID 56841945
- Mass difference
- 279.3 Da (the linker)
- DAC chemistry
- Maleimide to albumin Cys34
- With DAC half-life
- Days
- Without DAC half-life
- ~30 minutes
- Other name for non-DAC
- Modified GRF (1-29)
What DAC actually is
Drug Affinity Complex is ConjuChem's name for a maleimidopropionic acid group attached to the peptide. Maleimide reacts specifically with free thiols, and serum albumin has one: cysteine-34, the only free cysteine in the molecule. The result is a covalent bond, not the reversible association that fatty-acid conjugation produces in semaglutide.
Why covalent differs from reversible
This is the mechanistically interesting part. Semaglutide's fatty acid binds albumin reversibly, so a small free fraction is always available to act while the bound pool acts as a depot. DAC forms a permanent bond, so the peptide is attached to albumin for that albumin molecule's lifetime, and albumin's half-life is around nineteen days. The peptide's duration therefore tracks the carrier's, which is a different pharmacokinetic model entirely.
Research material referenced
CJC-1295 + Ipamorelin 5+5mg, third-party HPLC tested
The consequence for GH release
GHRH normally acts in pulses, and pituitary GH release is pulsatile. A compound producing continuous receptor stimulation is a different physiological stimulus from one producing brief pulses. Ionescu and Frohman examined this directly, reporting in the Journal of Clinical Endocrinology and Metabolism in 2006 that pulsatile GH secretion persists during continuous stimulation. The finding is relevant to what a long-acting GHRH analogue actually does.
How to tell which you have
Mass spectrometry. 3647.2 and 3367.9 are 279.3 apart, which is unambiguous on any instrument. Names are unreliable here because PubChem itself carries both 'with DAC' and 'no DAC' synonyms on a single record, and suppliers inherit that. A certificate stating a mass near 3368 describes the DAC-free peptide whatever the label says.
Which is used with ipamorelin
The non-DAC form is the more common pairing, on the reasoning that both compounds are then short-acting and produce a coordinated pulse rather than one brief and one sustained signal. That is a design rationale rather than a demonstrated advantage.
Quick reference
| With DAC | Without DAC (Mod GRF 1-29) | |
|---|---|---|
| Molecular weight | 3647.2 Da | 3367.9 Da |
| PubChem CID | 91971820 | 56841945 |
| Albumin binding | Covalent, via Cys34 | None |
| Half-life | Days | ~30 minutes |
| Stimulation pattern | Continuous | Pulsatile |
Frequently asked questions
- How much mass does DAC add?
- 279.3 Da. With DAC is 3647.2; without is 3367.9.
- Is DAC binding reversible like semaglutide's?
- No. Maleimide forms a covalent bond to albumin's Cys34, so the peptide stays attached for that albumin molecule's lifetime. Semaglutide's fatty acid binds reversibly.
- How do I tell the forms apart?
- By mass. Names are unreliable because PubChem carries contradictory synonyms on one record.
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.
Related questions researchers ask
- Is CJC-1295 the same as Modified GRF 1-29?
- What is the difference between DAC and no-DAC CJC-1295?
- Does Ipamorelin raise cortisol?
- Why are CJC-1295 and Ipamorelin blended together?
- How long is the half-life of CJC-1295 with DAC?
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.
- PubChemPubChem · CJC-1295 (CID 91971820)pubchem.ncbi.nlm.nih.gov
- PubChemPubChem · DAC:GRF (CID 56841945)pubchem.ncbi.nlm.nih.gov
- PubMedIonescu M & Frohman LA. J Clin Endocrinol Metab 2006 (PMID 17018654)pubmed.ncbi.nlm.nih.gov
- PubMedTeichman SL et al. J Clin Endocrinol Metab 2006 (PMID 16352683)pubmed.ncbi.nlm.nih.gov
- PubMedRaun et al., Ipamorelin, the first selective GH secretagogue. Eur J Endocrinol 1998 (PMID 9849822)pubmed.ncbi.nlm.nih.gov
- PubMedMüller TD et al., Ghrelin. Molecular Metabolism 2015 (PMID 26042199)pubmed.ncbi.nlm.nih.gov
- PubChemPubChem · Ipamorelin (CID 9831659)pubchem.ncbi.nlm.nih.gov
- TrialClinicalTrials.gov · GH-secretagogue trialsclinicaltrials.gov
- GuidelineGoogle: Creating helpful, reliable, people-first contentdevelopers.google.com
Written and reviewed by
The UK Peptides Editorial Team · Research library, UK Peptides
The editorial team is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate. Corrections are made in place and the review date updated.
More CJC-1295 & Ipamorelin articles
- CJC-1295 CAS Number and Chemical IdentityCAS 863288-34-0 resolves to the 3367.9 Da DAC-free peptide. A second CAS widely quoted for the DAC form does not resolve at all. Use mass instead.
- Modified GRF (1-29): What the Name MeansMod GRF (1-29) is CJC-1295 without the DAC linker, at 3367.9 Da. How it relates to sermorelin, and why the four substitutions remove a methionine.
- Half-Life: Why a Covalent Bond Changes EverythingMinutes for native GHRH, about thirty for Mod GRF, days for the DAC form. Each step is a specific chemical intervention against a specific clearance route.
- What Is Ipamorelin? Sequence, Receptor and SelectivityIpamorelin is a five-residue ghrelin receptor agonist, Aib-His-D-2-Nal-D-Phe-Lys-NH2, described as the first selective growth hormone secretagogue.
- Ipamorelin Sequence and Chemical IdentityAib-His-D-2-Nal-D-Phe-Lys-NH2, CAS 170851-70-4, CID 9831659, 711.9 Da. One name, one compound — unusually clean for this field.
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