CJC-1295: What the DAC Actually Does

CJC-1295 is the compound most often ordered incorrectly, and the reason is a three-letter suffix that suppliers sometimes omit. Getting it right takes two minutes of reading and saves an entire wasted experiment.

Two molecules, one name

Both forms are analogues of the first 29 residues of growth hormone releasing hormone — the fragment sometimes called GRF(1-29) — carrying four amino acid substitutions that protect it from enzymatic breakdown.

CJC-1295 without DAC is that modified fragment and nothing more. It is also, confusingly, sold as modified GRF(1-29). Its working life is short, on the order of minutes.

CJC-1295 with DAC adds a drug affinity complex: a maleimido-propionyl group that forms a covalent bond with a cysteine residue on circulating serum albumin. Albumin has a very long circulating half-life, so the peptide effectively hitches a ride and its presence extends from minutes to days.

Why the distinction changes the experiment

The GHRH axis is naturally pulsatile — the pituitary responds to bursts, not to a flat signal. A short-acting analogue produces something closer to a pulse; the DAC version produces sustained exposure. Those are different biological questions, and results from one form should never be quoted as evidence about the other.

• Without DAC — short exposure, pulse-like signalling, shorter study windows.
• With DAC — sustained exposure via albumin binding, multi-day study designs.
• Different molecular weights, so different certificate of analysis figures.
• Different reconstitution and stability planning.

Checking which one you have

The certificate of analysis settles it. The DAC version is measurably heavier because of the added complex, so the mass spectrometry result is the definitive check. If the datasheet gives a molecular weight matching the plain modified fragment, you have the version without DAC regardless of what the label says.

Handling

1. 1Equilibrate the sealed vial before opening — condensation is the first avoidable error.
2. 2Reconstitute slowly down the vial wall and swirl; the DAC linker does not appreciate vigorous handling.
3. 3Refrigerate, protect from light, and date the vial.
4. 4Aliquot when a study will run over several days rather than re-entering one vial repeatedly.

One last practical point: because the DAC version persists, contamination in the vial has longer to matter. Sterile technique and bacteriostatic diluent are not optional for extended protocols.