What Is CJC-1295? GHRH Analog Structure, With and Without DAC

Key takeaways

• CJC-1295 is a synthetic analog of the first 29 residues of growth-hormone-releasing hormone (GHRH(1-29), the same active fragment as sermorelin), modified for stability.
• Its peptide backbone is 29 amino acids long and carries four substitutions relative to native human GHRH(1-29): D-Ala at position 2, Gln at 8, Ala at 15, and Leu at 27.
• The single structural difference between the two CJC-1295 forms is DAC (Drug Affinity Complex): the DAC version appends a lysine linker bearing a maleimidopropionyl group at the C-terminus; the non-DAC version omits it.
• Non-DAC CJC-1295 (the bare modified GHRH(1-29), also catalogued as Mod GRF 1-29) has a molecular formula commonly given as C152H252N44O42 and an average mass near 3367.9 g/mol; the DAC version is heavier because of the added lysine-maleimide group.
• Ascend Bio Labs supplies CJC-1295 with a public, per-batch COA keyed to the batch ID on each vial, with independent third-party HPLC for purity and LC-MS for identity, all US-domestic.

CJC-1295 is one of the most frequently mislabeled compounds in research catalogs, because two structurally different molecules ship under the same name: a 'with DAC' version and a 'without DAC' version. This guide stays strictly structural. It covers what kind of molecule CJC-1295 is, the native sequence it is built on, the four substitutions that distinguish it from that native sequence, and the single chemical modification (DAC) that separates the two forms, along with sequence length, molecular formula, and molecular weight. Nothing here addresses what the compound does in any organism it is written for laboratory handling and characterization only.

Getting the structure right is also what lets you read a certificate of analysis for the material and confirm you received the form you intended. The substitutions fix the backbone the analyte should match; the presence or absence of the DAC group shifts the theoretical mass that LC-MS is asked to confirm. Each section below ties a structural fact to the practical handling or verification consequence that follows from it.

Peptide class: a GHRH(1-29) analog

CJC-1295 belongs to the class of growth-hormone-releasing hormone (GHRH) analogs. Native human GHRH is a 44-residue peptide, but its receptor-binding activity is retained by just the first 29 residues GHRH(1-29). That 29-residue fragment is the same active sequence catalogued elsewhere as sermorelin, and it is the scaffold CJC-1295 is built on. In structural terms, treat 'CJC-1295' as 'GHRH(1-29) with a defined set of stabilizing modifications' rather than as a description of any biological role.

Because it is a GHRH(1-29) analog rather than a ghrelin-mimetic, CJC-1295 is structurally distinct from the growth-hormone secretagogue peptides it is often catalogued beside. The pentapeptide Ipamorelin and the non-peptide small molecule MK-677 (ibutamoren) act on a different molecular target and bear no sequence relationship to GHRH. Its closest structural relative in a typical catalog is Tesamorelin, which is also a stabilized GHRH(1-44) or GHRH(1-29)-based analog the two are best understood as different chemical strategies applied to the same GHRH scaffold.

The native GHRH(1-29) sequence has a well-documented vulnerability: it is cleaved rapidly by the enzyme dipeptidyl peptidase-4 (DPP-4) at the bond after position 2, and the resulting fragment is inactive. CJC-1295's substitutions are best understood as edits made to that scaffold to resist that cleavage and other degradation a structural rationale, stated without any claim about effect in an organism.

• Class: GHRH analog, specifically based on GHRH(1-29).
• GHRH(1-29) is the same active fragment catalogued as sermorelin.
• Distinct from ghrelin-mimetic secretagogues (Ipamorelin, MK-677), which target a different receptor.
• Closest catalog relative by scaffold is Tesamorelin, another stabilized GHRH analog.

The four substitutions that define CJC-1295

What makes CJC-1295 a distinct molecule rather than plain GHRH(1-29) is a set of four amino-acid substitutions made to the 29-residue backbone. Reading by position, they are commonly given as: D-alanine in place of L-alanine at position 2; glutamine (Gln) replacing arginine at position 8; alanine (Ala) at position 15; and leucine (Leu) at position 27. These four edits are the structural signature of the molecule and are what an identity check is ultimately validating against.

Each substitution has a stated structural purpose. The D-Ala at position 2 is the most important: switching the second residue to the D-stereoisomer blocks the DPP-4 cleavage site, because the enzyme does not accept the D-configuration at that position. The position-15 alanine and the position-27 leucine are substitutions that reduce other degradation and oxidation liabilities of the native sequence, and the position-8 glutamine removes a residue prone to deamidation. Collectively these are the changes that turn the short-lived native fragment into a more robust analog.

Because these four substitutions are present in both the DAC and non-DAC forms, the bare four-substitution peptide (no DAC) is itself a named research compound: it is frequently catalogued as 'Modified GRF (1-29)' or 'Mod GRF 1-29' (sometimes 'CJC-1295 without DAC'). That naming overlap is the single biggest source of confusion in this product family, so it is worth stating plainly: Mod GRF 1-29 and 'CJC-1295 without DAC' refer to the same 29-residue, four-substitution peptide.

• Position 2: D-alanine (blocks DPP-4 cleavage).
• Position 8: glutamine (removes a deamidation-prone residue).
• Position 15: alanine.
• Position 27: leucine.
• The bare four-substitution peptide (no DAC) is the same molecule sold as 'Mod GRF 1-29'.

The DAC modification: the one structural difference between the two forms

DAC stands for Drug Affinity Complex, and it is the single structural feature that separates 'CJC-1295 with DAC' from 'CJC-1295 without DAC'. Both forms share the identical 29-residue, four-substitution backbone described above. The 'with DAC' form adds one thing to that backbone: a short chemical appendage at the C-terminus consisting of an extra lysine residue whose side chain is conjugated to a maleimidopropionyl (3-maleimidopropionyl) group. The 'without DAC' form simply ends at the 29-residue backbone with no such appendage.

The purpose of that maleimide-bearing group is bioconjugation chemistry: a maleimide reacts selectively with free thiol groups, so the DAC group is designed to form a covalent bond to a cysteine thiol on serum albumin once in a biological matrix. Structurally, then, the DAC version is best described as a peptide engineered to attach itself to a much larger carrier protein, whereas the non-DAC version is the bare modified peptide. This is a chemistry description of the molecule, not a claim about what it accomplishes in any test system.

For verification, the consequence is simple but important: the two forms have different molecular weights and therefore different expected masses on an LC-MS report. A vial labeled 'CJC-1295' that does not specify DAC status is structurally ambiguous, and a certificate of analysis is what resolves it the identity mass on the COA should correspond to whichever form was ordered. Treat 'with DAC' and 'without DAC' as two distinct analytes that happen to share a name and a backbone.

• DAC = Drug Affinity Complex.
• Both forms share the identical 29-residue, four-substitution backbone.
• 'With DAC' appends a C-terminal lysine bearing a maleimidopropionyl group; 'without DAC' omits it.
• The maleimide is designed to conjugate to a thiol (albumin) a chemistry description, not an effect claim.
• The two forms have different molecular weights and distinct expected LC-MS masses.

Sequence length, molecular formula, and molecular weight

The peptide backbone of CJC-1295 is 29 amino acids long in both forms the DAC group is a side appendage on a lysine, not an extension of the main 1-29 chain, though it does add atoms and mass. So while sequence length (29 residues) is shared, molecular formula and weight are not.

For the non-DAC form (Mod GRF 1-29 / 'CJC-1295 without DAC'), the molecular formula is commonly given as C152H252N44O42, with an average molecular weight of approximately 3367.9 g/mol. As with any peptide, you will see small rounding differences between sources depending on whether average or monoisotopic mass is quoted and how the termini are counted, but a clean LC-MS readout for this form should land near that figure within instrument tolerance.

The 'with DAC' form is heavier, because the added lysine plus maleimidopropionyl group contributes additional carbon, hydrogen, nitrogen, and oxygen atoms; its commonly cited average molecular weight is roughly 3647 g/mol, with the exact figure and formula depending on the source. The practical point for characterization is that the expected mass differs by the mass of that appendage so the COA's identity result, read against the form you ordered, is what confirms which molecule is in the vial. As with most basic peptides, both forms are typically supplied as a salt (acetate or trifluoroacetate), which raises the as-weighed powder mass per vial above the free-base figure.

• Backbone length: 29 amino-acid residues in both forms.
• Non-DAC: formula commonly C152H252N44O42, average mass approximately 3367.9 g/mol.
• With-DAC: heavier (commonly cited near 3647 g/mol) due to the lysine-maleimide appendage.
• Both are typically supplied as a salt, raising the as-weighed mass per vial above the free base.

Comparing the two forms at a glance

The table below summarizes the structural distinction between the two CJC-1295 forms. Every cell is a structural or chemical attribute no effect, dosing, or outcome statements and the only differences between the columns are the DAC appendage and the molecular formula and weight that follow from it.

The lyophilized vial, reconstitution, and storage

Research CJC-1295 (either form) ships as a lyophilized (freeze-dried) powder or thin cake in a sealed vial, typically under an inert headspace; freeze-drying leaves a dry solid that is far more stable in transit and storage than a solution would be. The visible cake can look small a few milligrams occupy little volume so fill weight should be read from the label, not judged by eye. That label should carry the compound name, the DAC status, the labeled peptide mass, and a batch or lot ID linking the powder to its certificate of analysis.

Reconstitution is the same arithmetic as for any lyophilized peptide: add bacteriostatic water (sterile water with a small amount of benzyl alcohol, preferred when a vial will be drawn from more than once) or plain sterile water slowly down the inner wall, then swirl gently rather than shaking. The resulting concentration equals the labeled peptide mass divided by the diluent volume added for example, 2 mL of water added to a 5 mg vial gives 2.5 mg/mL. The diluent volume is the only variable you control. For the full step-by-step volume calculation, see Reconstituting Lyophilized Peptides: BAC Water Math Step by Step.

Storage handling differs by state. As a sealed lyophilized powder, CJC-1295 is comparatively stable and is commonly stored cold and dry away from light, with freezing for longer-term holding. Once reconstituted, it is in solution and should be refrigerated, protected from light, used within a limited window, and protected from repeated freeze-thaw cycles. This is standard cold-chain handling for a research reagent, not a usage instruction. Ascend Bio Labs supplies CJC-1295 with a public, per-batch certificate of analysis keyed to the unique batch ID printed on each vial, with independent third-party HPLC for purity and LC-MS for molecular identity which is exactly what resolves the with-DAC versus without-DAC ambiguity and US-domestic synthesis, testing, storage, and shipping with insulated, tracked transit.

• Ships lyophilized; read fill weight and DAC status from the label, not by eye.
• Reconstitute with bacteriostatic or sterile water; swirl, do not shake hard.
• Concentration = labeled peptide mass / diluent volume added.
• Dry powder: store cold and dry, away from light. Reconstituted: refrigerate and avoid freeze-thaw cycling.
• A per-batch LC-MS identity result confirms which form (DAC or no-DAC) is in the vial.

Related research notes

• What Is Ipamorelin? Pentapeptide GH Secretagogue Specs
• What Is Tesamorelin? GHRH Analog Sequence and Molecular Weight
• What Is MK-677 (Ibutamoren)? Non-Peptide GH Secretagogue Profile
• Reconstituting Lyophilized Peptides: BAC Water Math Step by Step