CJC-1295 with DAC vs. without DAC: the structural difference

The comparison is at the C-terminus

CJC-1295 with DAC and CJC-1295 without DAC share the same core peptide scaffold, so the useful comparison is not a name-level comparison. It is a C-terminal chemistry comparison. <a href="/product/cp-010">CJC-1295 No-DAC</a> is the 30-residue analogue. <a href="/product/cp-011">CJC-1295 DAC</a> carries an added Drug Affinity Complex appendage. For in-vitro reference standard work, the key differences are mass, reactive functionality, HPLC behaviour, and storage control. [1]

Shared 30-residue scaffold

Both materials are built on a 30-residue analogue of GHRH(1-29). The shared scaffold is defined by four substitutions relative to the parent sequence family: D-Ala at position 2, Gln at position 8, Ala at position 15, and Leu at position 27. Those substitutions are part of the identity of both catalogue lines. A COA should therefore not describe the DAC and No-DAC forms as unrelated peptides. They share the same backbone sequence through the core chain. [2]

The practical implication is that sequence review starts the same way for both SKUs. The analyst checks the stated residue string, confirms the modified residue notation, and verifies the calculated mass for the base peptide. The No-DAC form is commonly reported near 3367.9 Da. If the COA mass sits in that range and no C-terminal appendage is listed, the identity file is consistent with the No-DAC reference standard. If the mass is roughly 280 Da higher, the analyst should look for the Drug Affinity Complex chemistry in the structure field. [3]

Substitution notation should be explicit because small notation gaps create large documentation errors. D-Ala-2 is not the same as L-Ala-2, and a missing stereochemical marker changes the defined molecular species. Gln-8, Ala-15, and Leu-27 should appear in the sequence or structure description, not only in a marketing name. A release file that lists only the common name forces the analyst to infer chemistry, which is weaker than recording the exact 30-residue structure. This is especially important when two vials share a base name but differ by terminal chemistry. [4]

This is the same discipline used in peptide mass spectrometry more broadly. A name can be ambiguous; a mass and structure are less forgiving. The guide to <a href="/research-guide/peptide-mass-spectrometry-identity">peptide mass spectrometry identity</a> explains why deconvoluted mass should be read with the exact molecular species in front of the analyst. For CJC-1295, that means the DAC appendage must be explicit, because it changes both exact mass and functional-group behaviour. [5]

What DAC adds

DAC stands for Drug Affinity Complex. In the CJC-1295 DAC material, the appendage is placed at the C-terminus and is commonly described as a lysine spacer plus a maleimidopropionic acid moiety. That additional structure raises the molecular weight from about 3367.9 Da for the No-DAC form to about 3647.9 Da for the DAC form. The mass difference is approximately 280 Da, large enough to show clearly in HPLC-MS identity data. [6]

The chemically important part is the maleimide group. Maleimides react with free cysteine thiols to form covalent thioether bonds. In an in-vitro characterisation workflow, that reactivity is relevant for serum albumin adduct studies, maleimide-hydrolysis tracking, and identity confirmation of the appended form. The maleimide group is not a decorative label. It is a functional group with measurable analytical consequences. [7]

The lysine spacer also matters. It separates the reactive maleimide from the core 30-residue peptide and contributes to mass, polarity, and chromatographic behaviour. If the COA merely lists CJC-1295 DAC without showing the appended structure or calculated mass, the technical file is incomplete. A release-quality record should state sequence, appendage, molecular weight, purity method, identity method, water content where measured, and storage recommendation. The product record for <a href="/product/cp-011">CP-011 CJC-1295 DAC</a> should align with that chemistry. [8]

Mass spectrometry signature

The clearest analytical separation between the two forms is the mass signature. CJC-1295 No-DAC should deconvolute near 3367.9 Da, while the DAC variant should deconvolute near 3647.9 Da before any deliberate adduct study. A 280 Da shift is not a rounding issue. It is a structural feature. If a reported DAC lot produces only the No-DAC mass, the appendage is absent or the identity assignment is wrong.

Charge-state distribution may also differ because the appendage alters ionisation behaviour. In electrospray HPLC-MS, both materials can appear as multiple charge states, but the deconvoluted neutral mass should resolve the identity question. The analyst should review raw spectrum, deconvolution settings, calibration status, and expected mass tolerance. A high-purity HPLC peak does not prove the DAC appendage on its own. It proves that one UV-detected component dominates under that chromatographic method.

For a robust identity check, pair HPLC purity with HPLC-MS mass confirmation. The HPLC trace answers whether the main UV peak dominates the integrated chromatogram, commonly at 214 nm or 220 nm. The mass spectrum answers whether that peak has the expected molecular weight. For DAC material, the method should also account for maleimide-related variants such as hydrolysed maleimide or controlled thiol adducts if those are part of the in-vitro characterisation plan.

HPLC retention and peak shape

The DAC appendage usually changes reversed-phase retention. A C-terminal maleimidopropionic acid group and spacer can shift the main peak later in a C18 gradient relative to the No-DAC form, although the exact direction and magnitude depend on column chemistry, ion-pairing system, gradient slope, temperature, and detection wavelength. A formed maleimide-thiol adduct should also be expected to move as a distinct chromatographic species, often later in the gradient under reversed-phase conditions. A 20-minute screening method and a 60-minute release method may not place the two materials at comparable timestamps.

The No-DAC form is structurally simpler. Its chromatogram is driven by the 30-residue peptide scaffold, counter-ion state, residual water, and synthesis-related impurities. The DAC form adds possible maleimide-related species. Hydrolysis of the maleimide ring changes mass and polarity. Thiol adduct formation, when studied deliberately, creates a new molecular species. These changes can appear as additional peaks or a shifted main peak depending on sample history and method.

Peak shape should be read with restraint. A clean, symmetric HPLC peak supports chromatographic homogeneity, but it does not answer every identity question. A shoulder could be a closely related impurity, conformer, hydrolysis product, salt-related artefact, or integration issue. The stronger review is method-linked: chromatogram, mass spectrum, sample preparation note, and acceptance criteria in one record. The article on <a href="/research-guide/reading-an-hplc-chromatogram">reading an HPLC chromatogram</a> gives the general framework.

Maleimide handling and storage

Storage requirements differ because the DAC form contains a reactive maleimide. Maleimides can hydrolyse in aqueous environments, and the rate depends on pH, temperature, buffer composition, and exposure time. The dry lyophilized vial should remain sealed, protected from light, and refrigerated or frozen according to the COA. A strict inert-atmosphere seal is especially useful for limiting moisture exposure before reconstitution. This is a chemical-protection step, not a marketing flourish.

The No-DAC form still deserves controlled storage, but it does not carry the same maleimide-specific hydrolysis concern. Keep the vial dry, cold, sealed, and documented. For both forms, avoid repeated warming of the sealed vial and record the first-open date. A cold-chain receiving log should include outer-package condition, cap and crimp condition, cake appearance, lot number, COA match, and storage location. Those fields make later HPLC or HPLC-MS anomalies easier to investigate.

Once reconstituted, the DAC form should be handled through a method-defined working window. If the study depends on the maleimide remaining reactive, the protocol should specify pH, buffer, temperature, contact time, and analytical confirmation. If the study intentionally forms an albumin or cysteine adduct, that adduct should be tracked as its own molecular species. Generic storage language is weaker than a molecule-specific note tied to the actual in-vitro method. For in-vitro albumin-conjugation work the maleimide reactivity is a feature, not a defect — but for chromatographic comparator runs, freshly reconstituted DAC material is the right reference, since aged stock will show progressive maleimide hydrolysis and a corresponding mass shift on HPLC-MS.

How to read the COA

A practical COA review starts with the SKU and sequence but should not stop there. For <a href="/product/cp-010">CP-010 CJC-1295 No-DAC</a>, the expected file should show the 30-residue analogue, the four core substitutions, molecular weight near 3367.9 Da, HPLC purity, HPLC-MS identity, and storage conditions. For <a href="/product/cp-011">CP-011 CJC-1295 DAC</a>, the file should add the C-terminal DAC appendage, molecular weight near 3647.9 Da, and maleimide-sensitive handling language.

The lot dossier should also separate purity from identity. A sample can show a dominant HPLC peak and still require mass confirmation to distinguish DAC from No-DAC. Conversely, a correct mass does not replace the need for purity data, residual solvent review, and water-content awareness. A complete release file links each claim to a named method: reversed-phase HPLC for area-percent purity, HPLC-MS for identity, Karl Fischer where water is measured, and GC headspace where residual solvents are listed.

A second review point is sample history. DAC material exposed to moisture, neutral-to-basic buffer, or thiol-containing reagents may no longer match the unopened-vial mass profile. The COA describes the released lot, not every later bench condition. If a working stock produces an extra peak, the investigation should compare unopened reference material, reconstituted stock, buffer blank, and any deliberate cysteine-containing component. That four-sample check separates supplier identity questions from local handling chemistry.

The comparison is therefore straightforward when the documentation is complete. Same 30-residue core. Different C-terminal appendage. About 280 Da mass difference. Different maleimide handling concerns. Distinct chromatographic and mass-deconvolution expectations. If those lines are visible, the two materials are easy to separate in a procurement review.

Summary

• CJC-1295 No-DAC is the 30-residue analogue near 3367.9 Da; the DAC variant adds a C-terminal appendage and sits near 3647.9 Da.

• The DAC appendage includes a lysine spacer and maleimidopropionic acid moiety, adding about 280 Da.

• Maleimide chemistry changes storage and in-vitro characterisation requirements, especially when thiol adducts are studied.

• Use HPLC for chromatographic purity and HPLC-MS deconvolution for exact identity; one method alone is not enough.

FAQ

What is the structural difference between CJC-1295 DAC and No-DAC?

They share the same 30-residue core analogue. The DAC form adds a C-terminal Drug Affinity Complex appendage with a lysine spacer and maleimidopropionic acid moiety.

How much mass does the DAC appendage add?

The appendage adds about 280 Da, moving the expected molecular weight from roughly 3367.9 Da to roughly 3647.9 Da.

Why does maleimide handling matter?

Maleimide can hydrolyse in aqueous conditions and can form covalent thioether bonds with free cysteine thiols. Those reactions change the analytical species being measured.

Can HPLC purity distinguish DAC from No-DAC?

HPLC helps compare chromatographic profiles, but HPLC-MS identity is needed to confirm the approximately 280 Da structural difference.

Frequently asked questions

References

1. Ionescu M., Frohman L. (2006). Pulsatile Secretion of Growth Hormone (GH) Persists during Continuous Stimulation by CJC-1295, a Long-Acting GH-Releasing Hormone Analog. The Journal of Clinical Endocrinology &amp; Metabolism. · DOI
2. Henninge J., Pepaj M., Hullstein I. et al. (2010). Identification of CJC‐1295, a growth‐hormone‐releasing peptide, in an unknown pharmaceutical preparation. Drug Testing and Analysis. · DOI
3. Timms M., Ganio K., Forbes G. et al. (2018). An immuno polymerase chain reaction screen for the detection of CJC‐1295 and other growth‐hormone‐releasing hormone analogs in equine plasma. Drug Testing and Analysis. · DOI
4. Kojima M., Hosoda H., Date Y. et al. (1999). Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. · DOI
5. Howard A., Feighner S., Cully D. et al. (1996). A Receptor in Pituitary and Hypothalamus That Functions in Growth Hormone Release. Science. · DOI
6. Merrifield R. (1963). Solid Phase Peptide Synthesis. I. The Synthesis of a Tetrapeptide. Journal of the American Chemical Society. · DOI
7. FIELDS G., NOBLE R. (1990). Solid phase peptide synthesis utilizing 9‐fluorenylmethoxycarbonyl amino acids. International Journal of Peptide and Protein Research. · DOI
8. Rauh M. (2012). LC–MS/MS for protein and peptide quantification in clinical chemistry. Journal of Chromatography B. · DOI