DAC linker comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-04-04. Where a claim depends on a specific study, the study is described rather than over-claimed.
Enzymatic protection is a separate mechanism from plasma protein binding. The four substitutions in the backbone reduce recognition by dipeptidyl peptidase IV, which normally cleaves the natural hormone within minutes. Without the reactive group, this resistance still yields only a short window of activity, generally reported in the range of tens of minutes. With it, reported half-lives in early human work extended to several days. The size of that gap is the main practical distinction between the two materials.
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.
CJC-1295 is a synthetic peptide built as a long-acting analogue of growth hormone-releasing hormone. Its backbone matches the first twenty-nine residues of the natural human hormone, with four amino acid substitutions added to slow enzymatic breakdown. A reactive maleimide group, commonly termed the drug affinity complex, allows the peptide to attach to circulating albumin after administration. That albumin attachment keeps the molecule in the bloodstream for an extended period instead of being cleared within minutes.
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.
| Property | Value | Notes |
|---|---|---|
| Duration with linker | Several days | Reported in early human work |
| Duration without linker | Tens of minutes | Short plasma residence |
| Albumin attachment site | Cysteine-34 | Covalent maleimide reaction |
| Primary receptor | Pituitary GHRH receptor | Stimulates growth hormone release |
| Downstream marker | Insulin-like growth factor 1 | Indirect measure of activity |
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.
Receptor level activity follows the canonical GHRH pathway. The peptide binds the GHRH receptor, a class B G protein coupled receptor on somatotroph cells of the anterior pituitary. Binding raises intracellular cyclic AMP, which promotes calcium entry and the release of growth hormone into the bloodstream. Because the molecule acts at the same receptor as the endogenous hormone, its effect is superimposed on the natural pulsatile rhythm rather than replacing it. Whether sustained receptor occupation leads to desensitization is not fully settled.
The peptide backbone corresponds to GRF(1-29), the first 29 residues of native growth hormone-releasing hormone, which retains most of the receptor-activating activity of the full-length molecule. Four substitutions distinguish the analog from the natural sequence: D-alanine at position 2, glutamine at position 8, alanine at position 15, and leucine at position 27. These changes slow cleavage by dipeptidyl peptidase IV, the enzyme that degrades native hormone in plasma within minutes. The outcome is improved enzymatic stability combined with a still brief residence time when no additional modification is present.
Naming in this area is inconsistent, and readers should treat product labels with care. In much of the literature and in vendor catalogs, the unqualified term refers to the albumin-binding version, while the version lacking the DAC group appears as modified GRF(1-29), mod GRF(1-29), or the same name with a without-DAC qualifier. Because one abbreviation has been applied to both materials, the only reliable way to identify a sample is to check the stated sequence and the presence of the linker.
Reports on this compound commonly follow serum growth hormone and insulin-like growth factor 1 across defined time windows. Protocols differ in sampling frequency, assay platform, and participant characteristics, which makes direct comparison between publications difficult. Some work focuses on pulsatile release patterns instead of average concentrations. Whether repeated exposure alters endogenous hormone rhythms over long periods remains an open question, and the formal literature is thinner than the volume of informal commentary implies.
Once in circulation, the peptide binds the growth hormone-releasing hormone receptor displayed on pituitary somatotroph cells. Receptor activation couples to Gs proteins, elevates intracellular cyclic AMP, and drives protein kinase A signaling inside the cell. That cascade increases discharge of growth hormone into the bloodstream. The analog therefore operates through a receptor pathway that already exists for the body's own releasing hormone, rather than through an engineered artificial target.
Clearance profiles diverge sharply between the two versions. The albumin-binding molecule stays in plasma for several days, whereas the unmodified analog is largely gone within about half an hour in reported work. Cleavage by dipeptidyl peptidase IV is a major contributor to the short life of the unmodified sequence. These gaps mean the two versions cannot be substituted for each other in study design or in reading results side by side.
== Potential risks == In December 2024, 38 scientists, including several synthetic biology researchers and two Nobel laureates, warned that the creation of mirror-image life could cause "unprecedented and irreversible harm" to human health and ecosystems worldwide. The reversed structure of mirror-image bacteria could allow them to evade many mechanisms critical for immunity and predation that have evolved to recognize natural-chirality structures. As a result, mirror-image bacteria could potentially escape immune defenses and invade natural ecosystems, leading to "pervasive lethal infections in a substantial fraction of plant and animal species, including humans." Given these risks, the scientists concluded that mirror-image organisms should not be created without compelling evidence of safety. As of January 2026, no researchers are known to be pursuing the creation of mirror life; several who had been pursuing it have since renounced it and signed on as coauthors on the 2024 paper. Since the publication of the 2024 paper, 96 biotechnology experts signed a statement agreeing with its conclusions, and attendees of the first international conference on mirror-image life largely agreed that it should not be created. Germany’s Central Commission for Biological Safety (ZKBS) issued a statement that while applied research on mirror biomolecules should continue, mirror bacteria could pose serious risks, and that "a broad scientific and societal debate" was necessary.
A proteome is the entire set of proteins that is, or can be, expressed by a genome, cell, tissue, or organism at a certain time. It is the set of expressed proteins in a given type of cell or organism, at a given time, under defined conditions. Proteomics is the study of the proteome.
==== Autoimmune diseases ==== Low plasma vitamin D concentrations have been reported for autoimmune thyroid diseases, lupus, myasthenia gravis, rheumatoid arthritis, and multiple sclerosis. For multiple sclerosis and rheumatoid arthritis, intervention trials using vitamin D supplementation did not demonstrate therapeutic effects.
Sources: en.wikipedia.org
=== Pharmacodynamics === Carfentanil acts as a highly selective agonist of the μ-opioid receptor. It showed affinity values (Ki) of 0.051 nM for the μ-opioid receptor, 4.7 nM for the δ-opioid receptor, and 13 nM for the κ-opioid receptor in rat brain. Thus, carfentanil displayed 90- and 250-fold selectivity for the μ-opioid receptor over the δ-opioid receptor and the κ-opioid receptor, respectively. With human proteins, the affinities were 0.024 nM for the μ-opioid receptor, 3.3 nM for the δ-opioid receptor, and 43 nM for the κ-opioid receptor, demonstrating 140- and 1,800-fold selectivity for the μ-opioid receptor over the δ- and κ-opioid receptors, respectively. Carfentanil appears to have higher affinity for the μ1-opioid receptor over the μ2-opioid receptor. Carfentanil has approximately 10,000 times the analgesic potency of morphine, 4,000 times the potency of heroin, and 20 to 100 times the potency of fentanyl in animal studies. The effects of carfentanil are reversed by μ-opioid receptor antagonists like naloxone and naltrexone, though higher than normal doses of these agents may be necessary in humans due to the extremely high potency of carfentanil.
== External links == "Epoprostenol". Drug Information Portal. U.S. National Library of Medicine. Archived from the original on October 28, 2020. "Epoprostenol sodium". Drug Information Portal. U.S. National Library of Medicine. Archived from the original on June 28, 2019.
=== Policy evaluation === Measuring the costs and benefits of strategies to combat AMR is difficult and policies may only have effects in the distant future. In other infectious diseases this problem has been addressed by using mathematical models. More research is needed to understand how AMR develops and spreads so that mathematical modelling can be used to anticipate the likely effects of different policies.
Sources: en.wikipedia.org
McGregor starred in Moulin Rouge! (2001) as the young poet Christian, who falls in love with the terminally-ill courtesan Satine (Nicole Kidman), for which his performance was widely praised and garnered McGregor his first Golden Globe Award for Best Actor – Motion Picture Musical or Comedy nomination. He also appeared in Ridley Scott's war film Black Hawk Down (2001) as John Grimes. He starred alongside Renée Zellweger in Down with Love (2003). He also portrayed the younger Edward Bloom in Tim Burton's critically acclaimed film Big Fish (2003) alongside Albert Finney, Jessica Lange, Alison Lohman and Billy Crudup. In the same period, he also received critical acclaim for his portrayal of an amoral drifter mixed up with murder in the drama Young Adam (also 2003), which co-starred Tilda Swinton. McGregor voiced the robot Rodney Copperbottom in Robots and the lead character in Gary Chapman's Valiant (both 2005). Also around this time, McGregor played two roles – one a clone of the other – opposite Scarlett Johansson in Michael Bay's science fiction action thriller film The Island (2005). He also headlined Marc Forster's 2005 film Stay, a psychological thriller co-starring Naomi Watts and Ryan Gosling.
Bokkoms is whole, salted and dried mullet and is a well-known speciality the West Coast region of South Africa. This salted fish is dried in the sun and wind and is eaten after peeling off the skin. In some cases it is also smoked.
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==== Pneumofathometer ==== A pneumofathometer is a device used to measure the depth of a diver by displaying the back-pressure on a gas supply hose with an open end at the diver, and a flow rate with negligible resistance in the hose. The pressure indicated is the hydrostic pressure at the depth of the open end, and is usually displayed in units of metres or feet of seawater, the same units used for decompression calculations. The pneumo line is usually a 0.25 inches (6.4 mm) bore hose in the diver's umbilical, supplied with breathing gas from the gas panel via a supply valve. Downstream from the valve there is a branch to a high resolution pressure gauge, a restriction to flow to the gauge, and an overpressure relief valve to protect the gauge from full panel supply pressure in case the pneumo line is used for emergency breathing gas supply. Each diver has an independent pneumofathometer, and if there is a bell, it will also have an independent pneumofathometer.
Sources: en.wikipedia.org
A maleimide moiety reacts with the thiol of cysteine-34, forming a covalent bond. The reaction occurs in circulation without enzymatic catalysis.
The group is intended to alter distribution and persistence, not receptor engagement. The peptide portion still binds the pituitary receptor, so the primary difference is duration rather than potency.
Not firmly. Early reports describe several days for the extended form, but independent confirmations are sparse, and values vary with assay method and study design.
It is a synthetic peptide analogue of growth hormone-releasing hormone. Four substitutions in its sequence make it more resistant to enzymatic degradation than the natural hormone. In the version carrying a drug affinity complex, the peptide binds albumin and remains in circulation for days.