CJC-1295 and Mod GRF 1-29: Understanding the Difference

CJC-1295 and Mod GRF 1-29: Understanding the Difference

Few naming conventions in research peptide supply cause as much confusion as those surrounding CJC-1295. The same catalogue may list CJC-1295, CJC-1295 with DAC, CJC-1295 without DAC and Mod GRF 1-29 — terms that in ordinary usage refer to two genuinely different molecules with different molecular weights, different CAS numbers and different analytical profiles. This article sets out the structural distinction.

The discussion here is confined to chemistry, nomenclature and analytical verification. No use of any kind is described.

The shared starting point

Both compounds derive from growth hormone-releasing factor, specifically the first 29 residues of GRF, commonly written GRF(1-29). That 29-residue fragment is the shortest portion retaining the core structural motif of the full 44-residue parent, and is itself catalogued separately as Sermorelin.

From this common origin, the two CJC-1295 variants diverge through different chemical modifications, and it is those modifications that account for the naming and the analytical differences.

CJC-1295 without DAC (Mod GRF 1-29)

This compound carries CAS number 863288-34-0, molecular formula C152H252N44O42 and a molecular weight of approximately 3,367.0 g/mol. Structurally it is GRF(1-29) with four amino acid substitutions introduced to modify the peptide’s stability characteristics under analytical and storage conditions.

The terms “CJC-1295 without DAC” and “Mod GRF 1-29” refer to this same modified 29-residue peptide. The second name is arguably the more descriptive of the two, since the molecule is a modified GRF 1-29 fragment and contains no DAC component at all. The persistence of “CJC-1295 without DAC” as a catalogue term is largely a matter of search convention rather than chemical logic.

CJC-1295 with DAC

CJC-1295 with DAC is the same modified 29-residue peptide chain carrying an additional conjugated component — the Drug Affinity Complex, from which DAC takes its name. This is a maleimidoproprionic acid linker attached to the peptide.

The consequence for analysis is immediate and unambiguous: the added linker increases the molecular weight to approximately 3,647.2 g/mol, a difference of roughly 280 g/mol against the without-DAC form. On a mass spectrum the two are trivially distinguishable. On a chromatogram they elute differently, because the linker alters the molecule’s hydrophobicity and therefore its retention behaviour on a reversed-phase column.

Why the distinction matters analytically

Because these are two separate chemical entities, a Certificate of Analysis for one tells you nothing about the other. Purity, mass confirmation and batch identity are all compound-specific. When cross-referencing supplier documentation, the reliable check is the stated molecular weight and CAS number rather than the product name.

• CJC-1295 without DAC / Mod GRF 1-29 — approximately 3,367.0 g/mol, CAS 863288-34-0.
• CJC-1295 with DAC — approximately 3,647.2 g/mol, incorporating the maleimidoproprionic acid linker.
• Sermorelin / GRF(1-29) — approximately 3,357.8 g/mol, the unmodified parent fragment.

Note that Sermorelin and CJC-1295 without DAC differ by only around 10 g/mol despite being distinct compounds. This is a case where mass alone is a weak discriminator and full chromatographic characterisation carries the burden of identification — a good illustration of why LC-MS and HPLC are run together rather than either in isolation.

Presentation and verification

Both variants are supplied as lyophilised powders in sealed glass research vials, typically specified at greater than 98% purity by HPLC with identity confirmed by LC-MS. As with all synthetic peptides, purity figures are batch-specific and should be read against the batch identifier on the accompanying documentation.

Corix Labs lists CJC-1295 with DAC 5mg and CJC-1295 MOD GRF 1-29 without DAC 5mg as separate catalogue entries, each with its own analytical specification.

Physical form and degradation chemistry

Both variants are lyophilised from solution and supplied as a dry cake or powder in a sealed glass vial. The freeze-drying step is not merely a convenience of shipping: peptide bonds hydrolyse in the presence of water, and removing water removes the dominant degradation route.

The two forms have somewhat different chemical vulnerabilities. The DAC-bearing variant carries a maleimide-derived linker, and maleimide chemistry is itself sensitive to hydrolysis under certain conditions. That introduces a degradation pathway the unmodified peptide does not have, and it is one reason the two forms should not be assumed to behave identically in storage merely because they share a peptide backbone.

Residual moisture content in a lyophilised cake is therefore a meaningful quality attribute for both, and particularly for the conjugated form.

Reading the documentation

When comparing Certificates of Analysis across suppliers for these compounds, several elements carry more weight than the headline purity figure.

• Whether the stated molecular weight matches the variant named. A document headed “CJC-1295” reporting a mass near 3,367 g/mol describes the without-DAC form regardless of what the title implies.
• Whether the analytical method is specified, including column, gradient and detection wavelength.
• Whether a batch identifier is present and matches the vial.
• Whether mass confirmation is reported alongside chromatographic purity, rather than purity alone.

Given how close Sermorelin and CJC-1295 without DAC sit in mass, documentation that reports only an approximate molecular weight without chromatographic characterisation leaves genuine ambiguity about which compound is described.

A note on blended preparations

Some research materials are supplied as blends in which two peptides share a single vial. These present additional analytical considerations, since the chromatographic profile contains peaks from both components and purity must be assessed per component rather than as a single figure. Corix Labs supplies a CJC-1295 without DAC and Ipamorelin blended vial alongside the single-compound presentations.

Corix Labs publishes analytical documentation for its research materials. See third-party testing reports for further detail on how batches are verified.

All materials referenced in this article are supplied strictly for laboratory research and analytical use. They are not licensed medicines and are not sold for use in humans or animals. Nothing in this article constitutes guidance on administration, preparation for use, or any clinical, therapeutic, diagnostic or cosmetic application.