If you have been reading about DAC linker and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-08-23. Where a claim depends on a specific study, the study is described rather than over-claimed.
Downstream of growth hormone, the liver and other tissues increase production of insulin-like growth factor 1, a mediator of many growth-promoting effects. Studies have documented elevated levels of both hormones after dosing, and the rise from the long-acting form persists longer than that produced by shorter-acting analogues. What remains unclear is whether sustained elevation of these markers translates into meaningful clinical benefit, and whether prolonged exposure carries risks that short trials could not detect.
CJC-1295 acts at the growth hormone-releasing hormone receptor, a G-protein-coupled receptor found on somatotroph cells in the anterior pituitary. Binding triggers a rise in cyclic AMP and calcium entry, which promotes release of stored growth hormone. Because the peptide mimics the body's own releasing hormone, it amplifies existing secretory pulses rather than driving continuous output. The size of the response therefore depends partly on the subject's own hormonal rhythm and feedback state.
Lyophilized material is generally stable for extended periods when held at minus twenty degrees Celsius or below and protected from moisture and light. In solution the peptide is more labile; bond hydrolysis, aggregation and oxidation of susceptible residues all proceed faster at ambient temperature. Repeated freeze and thaw cycles should be avoided because they promote clumping and loss of soluble material. The conjugated variant adds a further consideration, since the maleimide group can hydrolyze in aqueous buffer and lose its ability to react with albumin.
Laboratory handling centers on minimizing exposure to water, heat and oxygen before use. Working solutions are typically prepared in sterile water or a mild buffer, and any residual particulate matter is removed by filtration. When the powder dissolves slowly, a small proportion of acetonitrile or dilute acetic acid is sometimes added as a co-solvent. Containers are kept sealed and desiccated between uses. Records of lot number, reconstitution date and storage conditions support later comparison of results across experiments.
Identity and purity are established with reversed phase high performance liquid chromatography coupled to mass spectrometry. The chromatographic step separates the target peptide from truncated sequences and deletion products, while the mass measurement confirms the expected molecular weight to within a fraction of a dalton. Because the two common variants differ by the presence of the linker, mass alone can distinguish them in the unconjugated state. Amino acid analysis and peptide mapping are used when sequence level confirmation is required.
| Property | Value | Notes |
|---|---|---|
| Primary target | GHRH receptor | G-protein-coupled receptor on pituitary somatotrophs |
| Half-life, long-acting form | Several days | Extended by covalent albumin binding |
| Half-life, short form | About 30 minutes | Cleared rapidly by peptidases and kidneys |
| Route in studies | Subcutaneous injection | Used in the published human trials |
| Main measured effect | Rise in GH and IGF-1 | Surrogate markers rather than clinical endpoints |
Both forms act at the pituitary receptor for growth hormone-releasing hormone and increase growth hormone output, which in turn raises insulin-like growth factor 1. A long-acting analog produces sustained rather than pulsatile stimulation, and the physiological consequences of that pattern are not fully settled. Published human data on the extended form remain limited, and much of what circulates in discussion traces to early company reports rather than independent replication. How sustained exposure affects normal feedback remains an open question.
The distinguishing feature of the DAC form is a maleimide-containing group that reacts with the free thiol of cysteine-34 on human serum albumin. This reaction forms a covalent bond without enzymatic assistance, and it takes place after the peptide enters the bloodstream. Because albumin is abundant and long-lived, the attached peptide is carried through circulation far longer than an unmodified fragment would survive. The chemistry is a deliberate pharmacokinetic strategy rather than a change to receptor activity.
The compound emerged from work at a Canadian biotechnology firm in the early 2000s. Early human studies examined its effect on growth hormone and insulin-like growth factor 1 in healthy volunteers and in people with HIV-associated fat redistribution. Reports described sustained increases in both markers after a single injection. Development did not advance to regulatory approval, and the clinical programme was later discontinued. The molecule is now encountered mainly as a research chemical rather than a marketed medicine.
Two forms circulate in research settings and are frequently confused. One carries the drug affinity complex and is often written as CJC-1295 with DAC; the other lacks that group and is usually called modified GRF(1-29). The two share the same core sequence but differ sharply in how long they persist in blood. Products labelled only as CJC-1295 normally refer to the version carrying the complex. Documentation that omits the distinction leaves the intended molecule ambiguous.
CJC-1295 belongs to a class of synthetic peptides modeled on growth hormone releasing hormone, a forty-four amino acid signal produced by the hypothalamus. The compound is built from the first twenty-nine residues of the natural sequence, with four substitutions introduced at positions 2, 8, 15 and 27. These changes were designed to slow enzymatic breakdown while preserving receptor activation. The result is a peptide that is shorter than native GHRH and considerably more resistant to ordinary clearance pathways in circulation.
Two related forms appear under the CJC-1295 name. The simpler analogue, commonly written as modified GRF(1-29), carries the four substitutions but no additional conjugation. The second form attaches a maleimidopropionic acid linker to a lysine residue, a modification frequently called the drug affinity complex. That linker reacts with the free thiol on serum albumin to form a covalent bond. Because albumin has a long residence time in blood, the conjugated peptide stays in circulation far longer than the unconjugated analogue.
Like the CNO-III, this branch is also only significant in massive stars. The reactions are started when one of the reactions in CNO-III results in fluorine-19 and a photon instead of nitrogen-15 and an alpha particle, and continues
== Further reading == Hunt, Chris; et al. (August 28, 2023). "Shanidar et ses fleurs? Reflections on the palynology of the Neanderthal 'Flower Burial' hypothesis". Journal of Archaeological Science. 159 105822. Bibcode:2023JArSc.159j5822H. doi:10.1016/j.jas.2023.105822. S2CID 261325698. Pettitt, Paul; White, Mark (2012). The British Palaeolithic: hominin societies at the edge of the Pleistocene world. London: Routledge. ISBN 978-0-415-67454-6. Romagnoli, Francesca; Rivals, Florent; Benazzi, Stefano (2022). Updating Neanderthals: Understanding Behavioural Complexity in the Late Middle Palaeolithic. Academic Press. ISBN 978-0-12-821429-9. Stringer, C.; Gamble, C. (1993). In search of the Neanderthals. Thames and Hudson. ISBN 0-500-05070-8. Sykes, Rebecca Wragg (2020). Kindred: Neanderthal Life, Love, Death and Art. London: Bloomsbury Sigma. ISBN 978-1-4729-3749-0.
In the four tables below, very minor branches of decay (branching probability less than one in a million) are omitted. Spontaneous fission is also omitted, though larger than this for the heaviest even nuclei and detectable down to thorium. All nuclear data is taken from unless otherwise noted. The historical names of isotopes are recorded in. The energy release includes the total kinetic energy of all the emitted particles (electrons, alpha particles, gamma quanta, neutrinos, Auger electrons and X-rays) and the recoiling decay product nucleus; this corresponds to that calculated from atomic masses. The letter 'a' represents a year (from the Latin annus). In the tables (except for the neptunium series), the historical names of the naturally occurring nuclides are also given. Such names were used at the time when the decay chains were first discovered and investigated; the system listed was only finalized in the 1920s but it would be too confusing to give earlier names also. From these historical names one can thus find the modern isotopic designation. The three primordial chains given below—thorium, uranium/radium (from uranium-238), and actinium (from uranium-235)—each ends with its own specific lead isotope (lead-208, lead-206, and lead-207 respectively). All the lead isotopes are stable and are also present in nature as primordial nuclides, so their excess amounts in comparison with lead-204 (which has only a primordial origin) are required for accurate uranium–lead dating of rocks. Correlating more than one results in lead-lead dating, capable of even greater accuracy.
=== Intracellular receptors === Intracellular receptors exist freely in the cytoplasm, nucleus, or can be bound to organelles or membranes. For example, the presence of nuclear and mitochondrial receptors is well documented. The binding of a ligand to the intracellular receptor typically induces a response in the cell. Intracellular receptors often have a level of specificity, this allows the receptors to initiate certain responses when bound to a corresponding ligand. Intracellular receptors typically act on lipid soluble molecules. The receptors bind to a group of DNA binding proteins. Upon binding, the receptor-ligand complex translocates to the nucleus where they can alter patterns of gene expression. Steroid hormone receptors are found in the nucleus, cytosol, and also on the plasma membrane of target cells. They are generally intracellular receptors (typically cytoplasmic or nuclear) and initiate signal transduction for steroid hormones which lead to changes in gene expression over a time period of hours to days. The best studied steroid hormone receptors are members of the nuclear receptor subfamily 3 (NR3) that include receptors for estrogen (group NR3A) and 3-ketosteroids (group NR3C). In addition to nuclear receptors, several G protein-coupled receptors and ion channels act as cell surface receptors for certain steroid hormones.
Sources: en.wikipedia.org
=== Positive staining === Unlike negative staining, positive staining uses basic dyes to color the specimen against a bright background. While chromophore is used for both negative and positive staining alike, the type of chromophore used in this technique is a positively charged ion instead of a negative one. The negatively charged cell wall of many microorganisms attracts the positively charged chromophore which causes the specimen to absorb the stain giving it the color of the stain being used. Positive staining is more commonly used than negative staining in microbiology. The different types of positive staining are listed below.
X-linked intellectual disability refers to medical disorders associated with X-linked recessive inheritance that result in intellectual disability. As with most X-linked disorders, males are more heavily affected than females. Females with one affected X chromosome and one normal X chromosome tend to have milder symptoms. Unlike many other types of intellectual disability, the genetics of these conditions are relatively well understood. It has been estimated there are ~200 genes involved in this syndrome; of these ~100 have been identified. Many of these genes are found on the short 'p' arm of the chromosome, and duplications at Xp11.2 are associated with the syndromic form of the condition. X-linked intellectual disability accounts for ~16% of all cases of intellectual disability in males.
=== Pharmacokinetics === DOPR crosses the blood–brain barrier in rodents. The drug showed the highest brain/plasma ratio among DOM homologues in rodents, whereas 2,5-dimethoxyamphetamine (2,5-DMA) showed the lowest. This was involved in potency differences between the drugs.
About 80% of sales of the product evaporated "overnight" in 2012, per the president of Cargill Beef. Cargill stopped production in Vernon, California, and laid off about 50 workers as well as slowing production at other plants including a beef-processing plant in Plainview, Texas, where about 2,000 people were laid off. Many grocery stores and supermarkets, including the nation's three largest chains, announced in March 2012 that they would no longer sell products containing the additive. Some grocery companies, restaurants and school districts discontinued the sale and provision of beef containing the additive after the media reports. In April 2012, the USDA received requests from beef processors to allow voluntary labeling of products with the additive, and stated it planned to approve labeling after checks for label accuracy. Both BPI and Cargill made plans to label products that contain the additive to alleviate these concerns and restore consumer confidence. Following the USDA announcement to allow choices in purchasing decisions for ground beef, several school districts stated that they would opt out of serving ground beef with LFTB. By June 2012, 47 out of 50 U.S. states declined to purchase any of the product for the 2012–2013 school year while South Dakota Department of Education, Nebraska, and Iowa chose to continue buying it. On April 2, 2012, AFA Foods, a ground-beef processor manufacturer of finely textured beef owned by Yucaipa Companies filed for Chapter 11 bankruptcy due to a reduction in demand for ground beef, which it blamed on media attention.
=== Detection in body fluids === Diphenhydramine can be quantified in blood, plasma, or serum. Gas chromatography with mass spectrometry (GC-MS) can be used with electron ionization on full scan mode as a screening test. GC-MS or GC-NDP can be used for quantification. Rapid urine drug screens using immunoassays based on the principle of competitive binding may show false-positive methadone results for people having ingested diphenhydramine. Quantification can be used to monitor therapy, confirm a diagnosis of poisoning in people who are hospitalized, provide evidence in an impaired driving arrest, or assist in a death investigation.
Sources: en.wikipedia.org
It binds the growth hormone-releasing hormone receptor on pituitary somatotroph cells. Receptor activation raises cyclic AMP and promotes release of stored growth hormone granules. Because the peptide persists longer than natural releasing hormone, stimulation is prolonged rather than brief.
The drug affinity complex links the peptide to serum albumin through a covalent bond. The conjugate is too large to be filtered quickly by the kidneys and is shielded from enzymatic breakdown. This extends the apparent half-life from roughly minutes to several days.
Long-term safety and any clinical benefit are unestablished. Published human data cover small groups over limited periods and focus on hormone levels rather than health outcomes. Whether prolonged elevation of growth hormone and insulin-like growth factor 1 is beneficial or harmful is an open question.
The mass difference from the linker is large enough for routine detection by mass spectrometry. The unconjugated form gives a single sharp signal at its expected weight. Material that has already reacted with albumin shows a much higher mass and a broadened chromatographic peak.