CJC-1295 with DAC and CJC-1295 without DAC share the same 29-residue GHRH backbone; the difference is a single appended lysine carrying a maleimidopropionyl group that covalently conjugates the peptide to serum albumin. That one addition — 279.35 g/mol of it, taking the molecule from 3367.93 to 3647.28 g/mol — converts a minutes-scale probe into a days-scale one. In a CJC-1295 no DAC vs CJC-1295 DAC comparison, the choice is between studying pulsatile GHRH receptor signalling and studying continuous receptor occupancy, and the two answer genuinely different questions.
Both are supplied as lyophilized powder in 2, 5 and 10 mg vials with lot-matched HPLC certificates: CJC-1295 (No DAC / Mod GRF 1-29) and CJC-1295 with DAC, both listed under GHRH analogs. Both are research chemicals for in-vitro and preclinical laboratory work only, not for human or veterinary use.
CJC-1295 no DAC vs CJC-1295 with DAC at a glance
| Attribute | CJC-1295 (No DAC) | CJC-1295 with DAC |
|---|---|---|
| Also called | Modified GRF 1-29, Mod GRF 1-29 | CJC-1295 (the original literature name), DAC:GRF |
| Backbone | GHRH(1-29) with substitutions at positions 2, 8, 15 and 27 | The same tetrasubstituted backbone |
| Extra chemistry | None | Lys30 bearing a maleimidopropionyl group — the drug affinity complex |
| Length | 29 residues | 30 residues plus the linker |
| CAS number | 863288-34-0 | 863288-34-0 |
| Molecular formula | C152H252N44O42 | C165H269N47O46 |
| Molecular weight | 3367.93 g/mol | 3647.28 g/mol |
| Albumin interaction | None | Covalent conjugation to albumin Cys34 via maleimide–thiol addition |
| Reported persistence | Minutes — rapid clearance | Days in animal models |
| Receptor exposure profile | Pulsatile | Sustained and continuous |
| Distinctive handling risk | Standard peptide handling | Maleimide is thiol-reactive and hydrolyses at alkaline pH |
| Typical research question | Acute GHRH receptor signalling; pulsatility | Receptor desensitisation under continuous occupancy |
| Research sizes stocked | 2 mg, 5 mg, 10 mg | 2 mg, 5 mg, 10 mg |
| Purity | ≥99% HPLC, MS identity, lot-matched COA | ≥99% HPLC, MS identity, lot-matched COA |
A naming problem worth clearing up first
The two names are used inconsistently across the research-peptide market, and ordering the wrong one is a common and expensive mistake. In the primary literature, "CJC-1295" refers to the DAC-bearing molecule — the drug affinity complex is what the compound was named for. In vendor usage, "CJC-1295" very often means the version without DAC, whose accurate name is Modified GRF 1-29. We label both explicitly for that reason, and any protocol citing a published CJC-1295 study should confirm which molecule the source used before matching material to it.
The shared backbone: four substitutions and why they exist
Both molecules begin from GHRH(1-29), the N-terminal fragment established by decades of endocrine work to carry essentially all of the receptor-binding information of the 44-residue hormone. Four residues are replaced — at positions 2, 8, 15 and 27 — and each substitution addresses a specific degradation route: dipeptidyl peptidase-4 cleavage at the N-terminus, asparagine deamidation, and methionine oxidation. The result is a peptide that survives handling and circulation far better than native GHRH(1-29) without altering the receptor it acts on. Both compounds carry those four changes; neither differs from the other in receptor identity or in the mechanism of receptor engagement.
What the DAC actually is, chemically
The drug affinity complex is a maleimidopropionyl group attached through an appended lysine at position 30. Maleimide reacts selectively and rapidly with free thiols by Michael addition, and human serum albumin carries a single free cysteine at position 34 that is unusually accessible. The result is a covalent peptide–albumin conjugate: not a reversible association like the fatty-acid strategy used in incretin analogs, but a permanent bond. Albumin's size and long circulating life then shield the peptide from renal filtration and peptidase attack, which is why the reported persistence moves from minutes to days.
Two consequences follow directly, and both matter at the bench more than most users expect.
First, maleimide reacts with any accessible thiol, not only albumin's. Reconstituting the DAC version in a buffer containing dithiothreitol, beta-mercaptoethanol, free cysteine or glutathione consumes the reactive group before it ever meets albumin. The peptide remains present and will still bind the receptor, but it will behave like the non-DAC version pharmacokinetically — a failure mode that produces a plausible-looking result and no error message.
Second, maleimide hydrolyses. In aqueous solution, and increasingly fast above neutral pH, the ring opens to a maleamic acid that is no longer thiol-reactive. A DAC stock held in slightly alkaline buffer for an extended period loses its conjugating ability progressively, again without any visible change. Preparing DAC solutions fresh, keeping them at or slightly below neutral pH and using them promptly is the practical countermeasure.
Pulsatile versus continuous: the actual experimental difference
Native GHRH is released in pulses, and the somatotroph response is shaped by that pattern rather than by total exposure alone. The two compounds let a laboratory manipulate that variable directly.
The non-DAC version clears rapidly, producing a discrete exposure window that approximates a pulse. That makes it the appropriate tool for acute signalling studies, for on/off designs where a long tail would contaminate later arms, and for structure–activity work against native GRF 1-29 and sermorelin — our CJC-1295 vs sermorelin comparison covers that pairing.
The DAC version produces sustained receptor occupancy, which is a different pharmacological state rather than simply more of the same one. Continuous agonist exposure at a G-protein-coupled receptor commonly drives desensitisation, internalisation and downstream adaptation, and studying those processes requires exposure that persists. It is also the practical choice for long rodent protocols where frequent handling would itself be a confounder.
The reason this matters is that the two can produce opposite-looking results on the same endpoint and both be correct. A sustained-exposure arm showing an attenuated response over time is not contradicting a pulsatile arm showing a robust acute response — it is measuring adaptation the pulsatile design was built to avoid.
Which to choose for which research question
Choose the no-DAC version for acute and pulsatile designs
Receptor pharmacology in cells, acute signalling time-courses, washout designs, and any comparison against native or shorter GHRH analogs all favour the shorter-acting molecule. It is also the simpler compound to handle, with no thiol-reactive chemistry to protect.
Choose the DAC version for sustained-occupancy designs
Desensitisation, receptor downregulation, downstream IGF-1 adaptation and multi-week animal protocols favour the conjugated version. The trade-off is handling complexity and a shorter list of compatible buffers.
Combination designs pair either with a secretagogue
GHRH analogs and ghrelin-receptor secretagogues act at different receptors, which is why they are so often studied together. We stock co-formulated CJC-1295 with ipamorelin and CJC-1295 DAC with ipamorelin vials for those designs, and ipamorelin separately where single-component arms are needed for attribution. Our overview of the secretagogue landscape maps the family.
Handling, reconstitution and storage differences
The non-DAC version follows the standard peptide protocol: keep the sealed lyophilized vial frozen, bring it to room temperature before piercing the stopper so moisture does not condense on cold powder, run diluent down the vial wall, dissolve without shaking, and aliquot so stock is not repeatedly frozen and thawed. See our reconstitution guide and storage guide.
The DAC version needs three additions to that protocol. Avoid any diluent or buffer containing free thiols, since these consume the maleimide. Keep the pH at or slightly below neutral and avoid extended storage in solution, since maleimide hydrolysis is base-catalysed and irreversible. Prepare working solutions close to the time of use rather than holding them, and prefer single-use aliquots more strictly than usual, because each thaw extends the aqueous exposure that drives hydrolysis.
Concentration is a laboratory calculation, not a recommendation for use: a 5 mg vial reconstituted with 2 mL of diluent gives 2.5 mg/mL, or 2,500 mcg/mL, so 0.1 mL contains 250 mcg. Because the two molecules differ in mass by 279.35 g/mol — about 8 percent — equal mass concentrations are not equal molarities, and a side-by-side comparison of receptor pharmacology should be prepared in molar terms.
Purity, identity and COA checks
Request the lot-matched certificate for each vial and confirm HPLC purity with a visible chromatogram, a mass-spectrometric result matching the expected weight — 3367.93 g/mol for the non-DAC version and 3647.28 g/mol for the DAC version — and a lot number matching the vial. The mass check is the decisive one here, because the two products share a CAS number and differ by a single modification; a certificate quoting a mass consistent with the unmodified backbone on a vial labelled DAC is a direct contradiction worth resolving before use. For the DAC version specifically, ask whether the certificate reflects intact maleimide, since hydrolysed material has the same sequence, a mass 18 Da higher, and none of the conjugating behaviour that defines the product. Our COA guide explains what a complete document should contain.
Regulatory framing
Both compounds are supplied as research chemicals for laboratory use only. Neither is an approved medicine in the United States, and the published record for both is preclinical and investigational. Nothing on this page is a protocol for human or veterinary use. For broader context on this family of research tools, see our growth and performance research overview.