CJC-1295 Chemistry: GHRH Analog & the DAC Linker
A bench-level reference sheet on the GHRH(1-29) backbone behind CJC-1295, how the with-DAC and without-DAC variants differ on paper, how the chain is assembled, and what to read off the sequence before keeping one as a reference standard.
Sequence and Structure
CJC-1295 is an analog of the first 29 residues of growth-hormone-releasing hormone, the fragment written as GHRH(1-29). That stretch carries the portion of native GHRH needed to engage its receptor, which is why the 29-residue length recurs across this family of releasing peptides. CJC-1295 builds on that backbone with a small set of stabilizing substitutions, the kind of point edits a research chemist learns to read directly off the sequence.
The compound is supplied in two related forms. The without-DAC version, commonly labeled modified GRF(1-29), is the 29-residue chain on its own. The with-DAC version carries an added Drug Affinity Complex group, a maleimido-propionyl linker conjugated to a lysine side chain that allows the peptide to bind serum albumin. Both share the same core sequence, so on paper the only structural difference is the presence or absence of that linker, and that single change is what shifts molecular weight, chromatographic retention, and synthesis route.
Origin and Family
CJC-1295 sits in the GRF analog group, the growth-hormone-releasing branch of the GH-axis catalog. These are peptides modeled on GHRH itself, designed to keep the receptor-binding chemistry of the native hormone while improving handling and stability. The family resemblance is useful at the bench because related sequences tend to respond to the same synthetic strategies and the same analytical methods.
Within that group it is informative to read CJC-1295 alongside its neighbors. Sermorelin is the unmodified GHRH(1-29) fragment, the structural starting point this molecule modifies, while tesamorelin takes a different stabilization route with an N-terminal acyl group. Treating the GRF analogs as a family rather than as unrelated molecules makes it easier to anticipate how a given entry will behave on the column and in the freezer.
Synthesis
CJC-1295 is assembled by Fmoc solid-phase peptide synthesis. At 29 residues the chain is long enough to demand careful coupling but short enough to build as a single linear sequence without native chemical ligation. Fmoc chemistry uses base-labile protection and a mild acidic cleavage step, which keeps the stabilizing substitutions and any modified positions intact through the build. Coupling efficiency is the variable that most shapes final purity, so research-grade routes lean on optimized activators and careful resin loading to keep each step clean.
The two variants diverge at the linker stage. For the with-DAC form, the Drug Affinity Complex group is conjugated to a designated lysine side chain, a step done on resin or after cleavage depending on the route, which adds an operation that the plain GRF(1-29) sequence does not require. That extra chemistry is one reason the with-DAC material is more involved to make than the without-DAC form, a pattern that mirrors the on-resin modifications seen across the wider peptide catalog.
Characterization (Method)
Identity and purity for CJC-1295 are established with the same two complementary tools used across the reference catalog. Reversed-phase HPLC reports the purity figure, the percentage of total peak area attributable to the target peptide, and separates the main product from closely related deletion and truncation sequences. Mass spectrometry confirms identity by matching the measured mass to the expected mass for the sequence.
The DAC linker makes the mass check especially informative here. Because the with-DAC and without-DAC forms differ by the defined mass of the linker, mass spectrometry distinguishes the two variants cleanly and confirms that the conjugation step ran as intended. Reading the HPLC purity figure and the mass result together describes the chemistry of a given preparation, and documentation describing these methods is available on request rather than presented as a fixed specification.
Stability and Storage
As lyophilized powder, CJC-1295 is comparatively stable when kept cold, dry, and out of light. Long-term storage of the dry solid is typically at freezer temperatures, with the container protected from moisture so the hygroscopic powder does not pick up water on opening. Allowing a sealed vial to reach room temperature before it is opened helps avoid condensation on the cold contents.
Once reconstituted, the working solution is far less forgiving. Peptides in solution are subject to hydrolysis, oxidation, and adsorption to surfaces, so reconstituted material is generally held cold and used within a short window, with freeze-thaw cycles minimized. These are general handling principles for research peptides rather than claims about any one preparation, and the documentation for a given standard should be the reference of record for its own conditions.
What CJC-1295 Is Studied For (Chemistry Only)
In a research-chemistry context, CJC-1295 is of interest as a tractable model for GRF structure-activity work and for half-life engineering through conjugation. The matched with-DAC and without-DAC pair makes it a clean teaching case for how a single albumin-binding linker changes a peptide's mass, solubility, and chromatographic behavior without touching the underlying receptor-binding sequence. It also serves as a well characterized reference point when validating synthesis and analytical methods on related GRF analogs.
That framing is deliberately limited to the bench. These materials are reference standards for laboratory research only, and nothing here describes or implies any human or veterinary use or outcome. The value of CJC-1295 to a research chemist is as a chemistry subject, a defined sequence and a defined modification whose behavior under synthesis, analysis, and storage is well understood and worth knowing in detail.
CJC-1295 chemistry, answered
What is the difference between CJC-1295 with DAC and without DAC?
Both share the same GHRH(1-29) analog backbone. The with-DAC form carries a Drug Affinity Complex linker, a maleimido-propionyl chain that lets the peptide bind serum albumin and extend its circulating half-life. The without-DAC form, often labeled modified GRF(1-29), omits that linker and is the shorter-lived parent sequence. The DAC group is the only structural distinction, and it changes synthesis steps, mass, and chromatographic retention.
How is CJC-1295 synthesized?
CJC-1295 is assembled by Fmoc solid-phase peptide synthesis on a single linear 29-residue chain. The sequence carries stabilizing substitutions relative to native GHRH, and for the with-DAC variant the DAC linker is conjugated to a lysine side chain, typically on resin or after cleavage. The peptide is then cleaved, deprotected, and purified by reversed-phase HPLC.
How is CJC-1295 identity and purity confirmed?
Identity and purity are established by two complementary methods. Reversed-phase HPLC reports the purity figure and separates the target from related deletion and truncation sequences, while mass spectrometry confirms identity by matching the measured mass to the expected mass for the sequence, including the added mass of the DAC linker on the with-DAC form. Documentation describing these methods is available on request.
How should CJC-1295 reference standard be stored?
As a lyophilized powder, CJC-1295 is comparatively stable when kept cold, dry, and out of light, with long-term storage of the dry solid at freezer temperatures. Allowing a sealed vial to reach room temperature before opening helps avoid condensation. Once reconstituted, the working solution is less stable and is generally held cold, used within a short window, and protected from repeated freeze-thaw cycles.
This overview is provided for laboratory and research use only. It is educational chemistry reference material and is not for human or veterinary consumption. Buyers are responsible for compliance with all applicable laws and regulations.