CJC-1295 With and Without DAC: Albumin Conjugation and Exposure Pattern in Research

Both versions — CJC-1295 without DAC and CJC-1295 with DAC — share the same 29-amino-acid GHRH chain. The only difference is an added lysine carrying a maleimidopropionyl group that bonds covalently to serum albumin. That extra piece contributes 279.35 g/mol, raising the molecular weight from 3367.93 to 3647.28 g/mol, and converts a compound active for minutes into one active for days. Deciding between CJC-1295 no DAC and CJC-1295 DAC is thus a decision between pulse-like GHRH receptor stimulation and sustained receptor occupancy — two different research questions.

We offer both — CJC-1295 with DAC and CJC-1295 No DAC (Mod GRF 1-29) — as freeze-dried powder in 10, 5 and 2 mg vials, each lot with its own HPLC certificate, in our GHRH analogs category. They are research chemicals for in-vitro and preclinical lab use and nothing else.

First, sorting out the names

Suppliers of research peptides use these two names inconsistently, and buying the wrong compound is a common and expensive mistake. In the scientific literature, "CJC-1295" refers to the DAC-carrying molecule, because the drug affinity complex is where the name comes from. Many sellers, however, attach "CJC-1295" to the version without the DAC, whose correct name is Modified GRF 1-29. For that reason we name both variants unambiguously, and anyone basing a protocol on a published CJC-1295 paper should first confirm which of the two the authors worked with.

Shared backbone, four substitutions

Both molecules are derived from GHRH(1-29), the N-terminal part of the 44-amino-acid hormone that, as endocrinology has long established, holds nearly all of its receptor-binding capacity. Four positions — 2, 8, 15 and 27 — are swapped, each aimed at a specific breakdown route: DPP-4 cleavage at the N-terminus, asparagine deamidation, and methionine oxidation. The result survives bench handling and circulation much better than unmodified GHRH(1-29) while still acting at the same receptor. Both variants carry all four substitutions; they do not differ in which receptor they target or in the way they bind it.

The chemistry of the DAC

The DAC itself is a maleimidopropionyl group mounted on an additional lysine placed at position 30. Maleimides react quickly and selectively with free thiol groups via Michael addition, and human serum albumin has one exceptionally exposed unpaired cysteine, Cys34. Coupling gives a covalent peptide–albumin adduct — a permanent linkage, in contrast to the reversible fatty-acid binding exploited by incretin analogues. The large, long-lived albumin molecule then shields the peptide from both kidney filtration and protease attack, explaining why reported persistence rises from minutes to days.

Two practical consequences follow, and both bite harder at the bench than users tend to expect.

First, the maleimide will couple to any thiol it meets, not only to albumin. Reconstitute the DAC variant in a buffer with DTT, beta-mercaptoethanol, free cysteine or glutathione, the maleimide gets used up before albumin is reached. The peptide remains intact and binds its receptor normally, but it now behaves pharmacokinetically like the version without DAC — a failure that produces plausible data and gives no sign that anything went wrong.

Second, the maleimide hydrolyses. Water opens the ring to a maleamic acid that can no longer couple to thiols, and the reaction speeds up as the pH climbs above neutral. A DAC solution kept in a slightly basic buffer gradually loses its capacity to bind albumin, once more without any visible change. The practical safeguard is to prepare DAC solutions just before use, keep them at neutral pH or a little under, and not let them sit.

Pulsatile against continuous: the real experimental distinction

The body releases GHRH in bursts, and somatotrophs respond to the rhythm of those bursts rather than only to the total amount received. With this pair of peptides, the exposure pattern becomes something the researcher can set deliberately.

Without the DAC, the peptide is cleared fast, producing a short, well-defined exposure that resembles one secretory burst. This is ideal for acute signalling experiments, for on/off designs where lingering peptide would carry over into the next arm, and for structure–activity work alongside unmodified GRF 1-29 and sermorelin; see our CJC-1295 vs sermorelin article for that comparison.

With the DAC, the receptor stays occupied — a qualitatively different pharmacological situation, not simply more of the same signal. When a G-protein-coupled receptor is stimulated without pause, desensitisation, receptor internalisation and downstream adaptation usually follow, and investigating those processes needs long-lasting exposure. It is also the practical choice for extended rodent studies in which repeated handling of the animals would introduce its own confounding effects.

The consequence is that the two formats can yield results on the same endpoint that look contradictory yet are both correct. A sustained arm showing a response that declines over time is not at odds with a pulsed arm showing a strong acute effect; it simply captures the adaptation that pulsed exposure is designed to avoid.

Matching the version to the question

Choose no DAC for short, pulse-like designs

Receptor pharmacology in cells, acute time-course experiments, washout designs and head-to-head comparisons with native or shorter-acting GHRH analogues all call for the short-lived molecule. It is also simpler to work with, because there is no thiol-sensitive group to protect.

Choose DAC for designs needing continuous occupancy

Research on desensitisation, receptor downregulation, IGF-1 adaptation downstream, and animal studies lasting several weeks all lean towards the albumin-bound variant. The trade-off is stricter handling and fewer buffers that can safely be used.

Either version can be paired with a secretagogue

Because GHRH analogues and ghrelin-receptor secretagogues act through different receptors, they are often studied together. For such work we offer pre-mixed vials of CJC-1295 plus ipamorelin and of CJC-1295 DAC with ipamorelin vials, as well as ipamorelin alone for single-compound arms where you need to attribute effects cleanly. Our overview of the secretagogue landscape maps the whole family.

Differences in handling, reconstitution and storage

The version without DAC is handled like any standard peptide: store the unopened freeze-dried vial in the freezer, allow it to warm to room temperature before the stopper is punctured so that no moisture condenses on the cold powder, let the diluent run along the inside wall, dissolve by gentle swirling rather than shaking, and divide into aliquots to avoid repeated freeze–thaw. Details are in the reconstitution and storage guides.

The DAC version needs three extra precautions. Avoid any diluent or buffer that contains free thiols, because these destroy the maleimide. Keep the pH neutral or just below and do not store the peptide in solution for long, since base drives maleimide hydrolysis and the change cannot be reversed. Prepare working solutions immediately before they are needed and be even stricter than normal about single-use aliquots, as each thaw adds to the time spent in water, which is what drives the hydrolysis.

The arithmetic below is laboratory bookkeeping and not a usage suggestion. Put 2 mL of diluent into a 5 mg vial and the result is 2.5 mg/mL, i.e. 2,500 mcg/mL, so a 0.1 mL portion carries 250 mcg. Keep in mind that the mass gap between the two molecules is 279.35 g/mol — roughly 8 percent — which means matching mg/mL does not match molarity; plan any direct pharmacology comparison in molar units.

Purity, identity and certificate checks

Insist on the certificate issued for the exact lot in each vial, and confirm three items: purity by HPLC with the trace reproduced, a mass-spec figure agreeing with theory (without DAC, 3367.93 g/mol; with DAC, 3647.28 g/mol), and a lot number that matches the label. Here the mass measurement is what really distinguishes the products, since a single CAS number covers both and they differ by one modification; a DAC-labelled vial whose certificate reports the mass of the plain backbone is an inconsistency worth resolving before any experiment. Also ask, for the DAC product, whether the analysis confirms the maleimide is still intact: the hydrolysed material has an unchanged sequence and is 18 Da heavier, yet it can no longer couple to albumin at all. Our COA guide lists everything a complete certificate should contain.

Regulatory framing

Neither product is anything other than a research chemical for laboratory use. No marketing authorisation as a medicine exists for either one in the EU or the United States, and the published evidence base for both is still preclinical and investigational. Our growth and performance research overview places this group of tools in a wider context.