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 2026-02-21. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Peptide class | Synthetic GHRH analogue | Built on a 29 residue sequence |
| Primary target | GHRH receptor (GHRHR) | Class B G protein coupled receptor |
| Unconjugated half life | Minutes | Limited by protease degradation |
| Key modification | Four residue substitutions | Positions 2, 8, 15 and 27 |
| Common synonym | Modified GRF(1-29) | Usually denotes the form without DAC |
CJC-1295 is a synthetic peptide belonging to the growth hormone-releasing hormone analog family. It comprises twenty-nine amino acid residues derived from the N-terminal region of natural GHRH. The molecule incorporates several non-natural substitutions that increase resistance to enzymatic degradation. These modifications extend its activity compared with the native hormone fragment. Researchers use it to study pituitary growth hormone secretion in laboratory and clinical settings. This compound is distinct from native GHRH in its stability profile.
Two principal forms appear in the literature and in research supply. One carries a drug affinity complex, a maleimide-based group that forms a covalent bond with circulating albumin. This linkage slows clearance and produces a long-lasting elevation of peptide levels. The other form lacks that group and is often labeled MOD GRF(1-29). It has a much shorter circulation time. Both variants retain the same core receptor-binding sequence. Reported half-lives differ substantially between the two.
At the pituitary, the peptide binds the growth hormone-releasing hormone receptor on somatotroph cells. Receptor activation raises intracellular cyclic AMP and triggers release of stored growth hormone. Somatostatin and other hypothalamic signals modulate this response. Negative feedback from insulin-like growth factor 1 also influences output. The same regulatory architecture operates with the native hormone. Whether the synthetic analog alters feedback dynamics over repeated exposure remains an open question. Most published receptor work uses cell models rather than intact human systems.
Lyophilized material is typically stored at minus twenty degrees Celsius or lower. Keeping the vial dry and protected from light preserves peptide integrity. Repeated freeze-thaw cycles can cause aggregation or loss of activity. Once dissolved, solutions are generally kept at two to eight degrees Celsius. Stability data for reconstituted solutions vary, and long-term behavior is not fully established. Working aliquots reduce the number of times a stock container is opened.
Reverse-phase high-performance liquid chromatography is the standard tool for purity assessment. The technique separates the target peptide from truncated or modified byproducts. Mass spectrometry confirms molecular weight and supports sequence verification. Electrospray ionization and matrix-assisted laser desorption are both used. Amino acid analysis provides an independent check on composition. Purity values are commonly reported as area percentage from the chromatogram. Residual trifluoroacetate and water content are also measured in many quality programs.
CJC-1295 is a synthetic peptide designed as a long-acting analogue of growth hormone-releasing hormone (GHRH). Its structure derives from the first 29 amino acids of native GHRH, a fragment often called GRF(1-29). Four substitutions were introduced to slow enzymatic breakdown and extend activity relative to the natural sequence. The compound was developed by ConjuChem as part of a broader effort to improve the pharmacokinetic profile of peptide hormones. It is studied in laboratory and clinical research settings rather than appearing as a naturally occurring substance.
Two related forms circulate in technical discussion under the same family name. The original version carries a drug affinity complex (DAC) that binds covalently to serum albumin after administration, and this linkage substantially extends circulation time. A second form, frequently written as modified GRF(1-29) or CJC-1295 without DAC, lacks that linker and clears much faster. The naming is a frequent source of confusion because the shorthand CJC-1295 can refer to either form depending on the source. Reports sometimes fail to specify which variant was studied.
Renwick (1839), mechanical engineer, patent expert Oliver Wolcott Gibbs (1841), chemist, president of the National Academy of Sciences and the American Association for the Advancement of Science Robert Ogden Doremus* (1842), chemist and physician Cornelius Rea Agnew (1849), physician who helped founding the Manhattan Eye, Ear and Throat Hospital Henry Carrington Bolton (1862), chemist and bibliographer of science Stuyvesant Fish Morris (1863), physician, nephew of Hamilton Fish '27 Rudolph August Witthaus (1867), toxicologist Frederick Remsen Hutton (1873), engineer, president of the American Society of Mechanical Engineers Sylvanus Albert Reed (1874), aerospace engineer who developed the modern metal aircraft propeller, which won the 1925 Collier Trophy William Hallock (1879), physicist, professor at Columbia University William Barclay Parsons (1879), chief engineer of the first line of the New York City Subway system, founder of multinational engineering firm Parsons Brinckerhoff Michael I. Pupin (1879), physicist, winner of the Pulitzer Prize for biography Henry Crampton (1893), evolutionary biologist Harold Jacoby (1894), astronomer and professor at Columbia University John Duer Irving (1896), geologist, professor at Sheffield Scientific School of Yale University Richard Weil (1896), physician, professor at Weill Cornell Medicine, son-in-law of Isidor Straus Hans Zinsser (1899), physician, bacteriologist, prolific author Marston T.
== References == 11. Website publication of Silver Book: The Silver Book and the NPU Format for Clinical Laboratory Science Reports Regarding Properties, Units, and Symbols . Published Online: 2017-04-25; Published in Print: 2017-04-25
Protein biosynthesis or protein synthesis (also known as proteosynthesis) is a core biological process, occurring inside cells, balancing the loss of cellular proteins (via degradation or export) through the production of fresh proteins. Proteins perform a number of critical functions as enzymes, structural proteins or hormones. Protein synthesis is a very similar process for both prokaryotes and eukaryotes but there are some distinct differences. Protein synthesis can be divided broadly into two phases: transcription and translation. During transcription, a section of DNA encoding a protein, known as a gene, is converted into a molecule called messenger RNA (mRNA). This conversion is carried out by enzymes, known as RNA polymerases, in the nucleus of the cell. In eukaryotes, this mRNA is initially produced in a premature form (pre-mRNA) which undergoes post-transcriptional modifications to produce mature mRNA. The mature mRNA is exported from the cell nucleus via nuclear pores to the cytoplasm of the cell for translation to occur. During translation, the mRNA is read by ribosomes which use the nucleotide sequence of the mRNA to determine the sequence of amino acids. The ribosomes catalyze the formation of covalent peptide bonds between the encoded amino acids to form a polypeptide chain. Following translation the polypeptide chain must fold to form a functional protein; for example, to function as an enzyme the polypeptide chain must fold correctly to produce a functional active site.
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== Dosage and imaging == The typical adult dose for a lung imaging study is 40-150 Megabecquerels (1-4 mCi) (containing between 100,000 - 200,000 albumin particles). The particle burden should be lowered for most pediatric patients and lowered to 50,000 for infants. The use of more than 250,000 particles in a dose is controversial as little extra data is acquired from such scans while there is an increased risk of toxicity. Patients with pulmonary hypertension should be administered a minimum number of particles to achieve a lung scan (i.e. 60,000). In any patient by administering a greater quantity of particles than necessary for the diagnostic procedure increases the risks of toxicity. Because of gravity effects, people administered 99mTc MAA should be in the supine position to ensure as even a distribution of particles throughout the lungs as possible. The total percentage of particles trapped in the lungs can be determined through a whole body scan after the administration of 99mTc MAA through the equation:
In October 2023, former Mongolian president Elbegdorj Tsakhia wrote to CNN, expressing his opposition to the death penalty and he cited Singapore as an example. Stating that Mongolia had abolished capital punishment and the crime rate in Mongolia never increased in the aftermath, Elbegdorj stated that he was concerned with the past 16 executions of low to mid-level drug traffickers in Singapore since March 2022, especially the July 2023 hanging of Saridewi Djamani (Singapore's first female to be put to death since 2004), and while he avers his respect for Singapore in terms of its prosperity and stability, Elbegdorj hoped that Singapore could re-evaluate the effectiveness of using the death penalty to curb drug crimes in favour of eventual abolition, due to the death penalty not able to fully uproot the cause of drug trafficking. He also stated that with the newly elected president Tharman Shanmugaratnam taking office, he hoped that the president could affirm the presidential powers of granting clemency to those on death row to soften the government's retentionist stance on capital punishment. In 2024, anti-death penalty activist Kokila Annamalai was the first activist within Singapore to publicly refuse to comply with the Protection from Online Falsehoods and Manipulation Act (POFMA) after the Singaporean government accused her of posting false information about its actions on social media concerning its use of the death penalty.
Depending on the species, an adult earthworm can be from 10 mm (0.39 in) long and 1 mm (0.039 in) wide to 3 m (9.8 ft) long and over 25 mm (0.98 in) wide, but the typical Lumbricus terrestris grows to about 360 mm (14 in) long. Probably the longest worm on confirmed records is Amynthas mekongianus that extends up to 3 m (10 ft) in the mud along the banks of the 4,350 km (2,700 mi) Mekong River in Southeast Asia. From front to back, the basic shape of the earthworm is a cylindrical tube-in-a-tube, divided into a series of segments (called metameres) that compartmentalize the body. Furrows are generally externally visible on the body demarking the segments. Dorsal pores and nephridiopores exude a fluid that moistens and protects the worm's surface, also allowing it to breathe. Except for the mouth and anal segments, each segment carries bristlelike hairs called lateral setae used to anchor parts of the body during movement. Species may have four pairs of setae on each segment or more than eight sometimes forming a complete circle of setae per segment. Special ventral setae are used to anchor mating earthworms by their penetration into the bodies of their mates. Generally, within a species, the number of segments found is consistent across specimens, and individuals are born with the number of segments they will have throughout their lives, growth in size being by enlarging existing segments rather than by adding new ones.
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The names are often used interchangeably in casual writing, but they are not strictly identical. Modified GRF(1-29) refers to the unconjugated analogue carrying only the four substitutions. The version sold as CJC-1295 with DAC includes the albumin binding linker and clears much more slowly.
DAC stands for drug affinity complex, a term describing the maleimidopropionic acid linker. This group forms a covalent bond with the cysteine residue on serum albumin after administration. The resulting adduct is what extends the circulating half life from minutes to days.
No. It is entirely synthetic and does not correspond to any known endogenous peptide. The design starts from human growth hormone releasing hormone and introduces deliberate substitutions. Any biological effect comes from mimicking the natural hormone at its receptor.
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.