CJC-1295 with DAC vs without DAC: Two Different Molecules

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The catalog name “CJC-1295” is used for two different molecules. They share a nickname. They do not share a mass.

CJC-1295 no DAC is Modified GRF(1-29): a tetrasubstituted GHRH(1-29) amide, formula C152H252N44O42, mass 3367.9 g/mol, CAS 863288-34-0, listed as a 2 mg lyophilized vial. CJC-1295 with DAC is that same backbone plus a C-terminal lysine carrying a maleimidopropionic acid (MPA) Drug Affinity Complex. Published structural descriptions put the DAC analogue near 3647 g/mol, formula in the C165 range, CAS 446262-90-4, also 2 mg lyophilized. The mass gap is about 280 Da. That gap is the identity test.

A tube labeled “CJC-1295” without the qualifier has not identified the reagent.

CJC-1295 without DAC is Mod GRF(1-29) at 3367.9 g/mol. With DAC the mass is about 3647 g/mol. The gap is the identity test.

Two names, two covalent structures

The no-DAC analogue carries four substitutions relative to native GHRH(1-29): Ala2 → D-Ala, Asn8 → Gln, Gly15 → Ala, and Met27 → Leu (or norleucine in some literature descriptions). Those substitutions reduce enzymatic clearance of the short fragment. They do not add an albumin-binding group.

The DAC analogue is not a different set of those four substitutions. It is the modified backbone plus the maleimide-bearing handle. In albumin-containing matrices the maleimide can form a thioether with Cys34 on serum albumin. After that reaction the peptide is no longer a ~3.6 kDa solute. The no-DAC peptide has no maleimide. It cannot form that adduct.

Both listings are USA manufactured, QC tested, 99%+ purity by HPLC and Mass Spectrometry, with a certificate of analysis as documentation. Those claims describe quality of a named analogue. They do not make the two analogues interchangeable. A COA that reports a single main-peak purity without an observed mass cannot tell a receiving lab which CJC-1295 it was issued.

The 280 Da gap

Reversed-phase HPLC reports purity as the area of the main peak. A no-DAC peptide at 99% and a DAC peptide at 99% can produce equally clean chromatograms. HPLC area percent does not name the peak.

Electrospray mass spectrometry does. The no-DAC analogue should give an envelope consistent with 3367.9 Da. The DAC analogue should give an envelope consistent with ~3647 Da. Seeing 3368 on a vial labeled “with DAC” is a mis-supply, a missing handle, or a documentation error. Seeing 3647 on a vial labeled “no DAC” is the same problem in reverse.

Native GHRH(1-29) amide sits close to the no-DAC mass, on the order of 10 Da lower. Low-resolution “about 3300” is how those two get confused. High-resolution mass, or a fragment that reports D-Ala2, Gln8, Ala15, or Leu27, removes that ambiguity.

Purity and identity stay orthogonal. The correct analogue at 95% is still the analogue named in the method. The incorrect analogue at 99% is still the wrong ligand.

Published half-life figures are about which analogue, not which to buy

The DAC was added so the peptide would persist in albumin-containing biological matrices. Published pharmacokinetic work on the DAC analogue reports an apparent plasma half-life on the order of several days, clustering around 5.8 to 8.1 days depending on the model. The no-DAC analogue is the short-acting species, commonly cited near 30 minutes in research models.

Those numbers are properties of specific experimental systems. They are not in vitro assay concentrations, and they are not a reason to pick a vial. They exist here for one reason: a paper that reports a multi-day half-life is describing the DAC analogue. A paper that reports a short pulse is not.

The blend is a second identity problem

The CJC-1295 + ipamorelin blend is a co-lyophilized cake: ipamorelin plus CJC-1295 no DAC (Modified GRF 1-29). Two peptides. Two masses (~712 Da and ~3368 Da). An HPLC trace of that vial should show at least two peptide peaks. Treating the blend as “CJC-1295,” or as “ipamorelin,” is an identity error.

Purchase records, freezer labels, and notebook headers need the qualifier. “CJC-1295, 2 mg, lyophilized” is incomplete. “CJC-1295 with DAC, observed mass ~3647 Da” is complete. “CJC-1295 no DAC / Mod GRF 1-29, observed mass 3367.9 Da” is complete.

The DAC maleimide is chemically more reactive than the no-DAC amide. Thiol-containing diluents, high pH, and prolonged aqueous storage are not equivalent conditions for the two lots. Bacteriostatic water is the vehicle named on both listings. It does not erase the difference in the peptide. This article does not assign reconstitution volumes.

Lyophilized storage is −20 °C. Warm the closed vial before opening. Keep the stopper in. Return the dry remainder to the freezer.

What this page is not

This page is not a reconstitution protocol and it is not a growth-hormone paper. It does not assign volumes. It does not treat published half-life figures as a shopping argument. The table is the job: which analogue, which mass, which live 2 mg listing.

You do not need an albumin-conjugation recipe to pick a vial. You need to know that no-DAC is 3367.9 g/mol and DAC is ~3647 g/mol, and that a blend cake contains the no-DAC analogue plus ipamorelin.

How the two 2 mg cakes actually sit in a freezer

A DAC cake and a no-DAC cake can share a box, a nickname, and a 99% HPLC line. They cannot share a mass. Label working tubes with CAS or with “DAC / no DAC,” not with “CJC.” CAS 446262-90-4 is the DAC construct. CAS 863288-34-0 is Mod GRF(1-29).

If the work is a two-analogue panel, that is two lots and two observed masses. Do not dissolve one analogue into a tube that previously held the other and call it a dilution. The maleimide on the DAC lot is a real chemical difference in thiol-containing matrices. Catalog material in this line is QC tested, 99%+ by HPLC and Mass Spectrometry, listed since late 2010. Expect the certificate to name the analogue. Still confirm the mass.

Conclusion

CJC-1295 without DAC is Modified GRF(1-29), 3367.9 g/mol, CAS 863288-34-0. CJC-1295 with DAC is the same backbone plus Lys-MPA, about 3647 g/mol, CAS 446262-90-4. The ~280 Da gap is how a laboratory tells them apart.

For in vitro laboratory use, the catalog lists CJC-1295 with DAC as the 2 mg DAC analogue, CJC-1295 no DAC as the 2 mg Mod GRF(1-29) analogue, and the CJC-1295 + ipamorelin blend as a co-lyophilized two-peptide cake. Confirm the mass. Do not let the nickname stand in for the analogue.