This is a working overview of DAC, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
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.
| 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 |
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.
Lyophilized peptide powder is comparatively stable when kept dry, cold, and protected from light. Once dissolved, the molecule is vulnerable to deamidation, oxidation, and aggregation, with the rate depending on pH, buffer composition, and temperature. Alkaline conditions and repeated freeze-thaw cycles accelerate loss of the intact peptide. The methionine present in the native sequence is a known oxidation site, which is one reason it was replaced in the modified fragment. Suppliers typically recommend cold storage of solutions and use within a short window.
Analytical confirmation usually relies on reversed-phase high-performance liquid chromatography for purity and on liquid chromatography coupled to mass spectrometry for identity. Mass data reveal the expected molecular mass and can flag truncated or oxidized species. Amino acid analysis and peptide mapping provide sequence-level verification. Immunoassays are used in some biological matrices, but antibodies raised against one releasing-hormone analog may cross-react with another. Reported purity figures depend heavily on the method used, so comparisons between suppliers require matching the analytical approach.
Binding of the peptide to the growth hormone-releasing hormone receptor on pituitary somatotrophs triggers a G protein coupled cascade that raises cyclic AMP and opens calcium channels. The result is greater secretion of growth hormone into the bloodstream. Because the peptide acts at the same receptor as the natural hypothalamic hormone, its effect is amplified pulse size rather than an entirely separate release pathway. Receptor binding alone does not determine the response, since somatostatin tone and other inputs modulate the final output.
The albumin-binding version stays in circulation for days, because covalent attachment to serum albumin shields the peptide from rapid filtration and degradation. Reported half-lives for this form fall in the range of several days. The version without the linker is cleared in minutes, with estimates often near thirty minutes in animal work. These figures come from small studies and vary with assay method, species, and route, so they are best read as approximate rather than fixed constants.
The dividing feature between the two forms is a maleimide-based drug affinity complex, abbreviated DAC. In the DAC-bearing version, a linker attaches the peptide to serum albumin after administration, and that association slows removal from plasma. The version lacking DAC appears in catalogs as MOD GRF(1-29) or tetrasubstituted GRF(1-29). Because informal writing treats both as one item, comparisons drawn from such sources routinely blend measurements taken from two molecules with substantially different behavior.
Four amino acid substitutions separate the modified backbone from the parent GRF(1-29) sequence. These changes reduce recognition by dipeptidyl peptidase IV and related proteases, extending the interval before degradation. Development work in this area sought longer-acting GHRH analogs for endocrine investigation. Published descriptions treat the substitution set as a defining property of the core sequence, while the albumin-binding linker is described separately as an optional addition to that same backbone.
CJC-1295 is a synthetic peptide analog of growth hormone-releasing hormone, constructed on the 29-amino-acid fragment designated GRF(1-29). The name began as an internal development code during the 1990s and later spread through research supply catalogs and discussion forums. The molecule does not occur in nature; its sequence is engineered rather than isolated from tissue. Two related compounds are sold under this single label, and they differ by one appended chemical group that strongly influences how long the peptide remains in circulation.
Here, a stock solution of glutamine is added in increasing increments with a high-accuracy instrument and diluted to the same volume in volumetric flasks. The result is 4 standard solutions with varying known concentrations (along with a blank for instrument calibration). The final concentration in each is calculated using the formula for molar concentration.
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=== Mechanism of action === Tazarotene is selective for two types of retinoic acid receptors, RAR-γ and RAR-β. Like all retinoids, it affects the ability of keratinocytes in the epidermis to proliferate and differentiate. It does so by upregulating filaggrin expression and downregulating the expression of keratinocyte transglutaminase, ornithine decarboxylase, involucrin, epidermal growth factor receptor, and various keratins.
In 1992, whilst studying for his PhD, he also ran the London Marathon, in a time of 4 hours and 41 minutes, to raise money to buy a computer for a young boy with physical disabilities. Skinner's PhD involved developing genetic tests to detect congenital adrenal hyperplasia in children. He had work published in a number of scientific journals. In 1994 he had his work published in Human Molecular Genetics. In 1994, Skinner married Dr. Monica Schneider (also a molecular biologist), and in 1996 their son James was born. From 1994 to 1996 Skinner worked as a Post-Doctoral Research Fellow at Vanderbilt University Medical Center, in Nashville, Tennessee. The work he carried out there involved gene sequencing and protein purification of cytochrome P450 enzymes. His work was published in the Journal of Biological Chemistry. From 1996 to 1997 Skinner took care of his infant son, James, whilst his wife continued to work at Vanderbilt University Medical Center.
Sources: en.wikipedia.org
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== Detection of citrullinated peptides and proteins == Citrullinated peptides and proteins can be detected using antibodies targeting the citrullinated residues, or detected using mass spectrometry-based proteomics technologies. Citrullination of arginine results in a monoisotopic mass increase of +0.984016 Da, which can be measured with mass spectrometry. The mass shift is close to the mass difference between the different peptide isotopes of +1.008665 which can be mistaken for a citrullinated peptide, especially on low-resolution instruments. However, this is less of an issue with modern high resolution/high accuracy mass spectrometers. Furthermore, the mass shift is identical to the mass shift caused by deamidation of the amino acid asparagine or glutamine side chain, which are common modifications. Citrulline residues can be chemically modified with butanedione or by biotinylation prior to analysis, leading to a different mass shift, and this strategy has successfully been used to facilitate identification by mass spectrometry. Another approach is to utilize the neutral loss of isocyanic acid (HNCO) from citrulline residues when submitted to low energy collision induced dissociation fragmentation in mass spectrometers. The loss causes a mass shift of −43.0058 Da, which can be utilized by mass spectrometers to predominantly select citrullinated peptides for fragmentation (sequencing). Finally, the loss of positive charge at physiological pH caused by citrullination can be utilized. Prior to bottom-up proteomics analysis, proteins are enzymatically cleaved into peptides.
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=== Cellulose nanocrystals === Cellulose nanocrystals (CNC) are rod like particles formed by the acid hydrolysis of native cellulose fibers, most commonly using sulfuric or hydrochloric acid. Disordered sections of native cellulose are hydrolysed and after careful timing, the remaining crystalline sections can be retrieved from the acid solution by centrifugation and dialysis against water. Their final dimensions depend on the cellulose source, its history, the hydrolysis conditions and the purification procedures. CNCs are commercialised by various companies that use different sources and processes, leading to a range of available products.
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In 1210, all Jewish householders in England were imprisoned in Bristol and a hefty levy of 60,000 or 66,000 marks was imposed on them. During the Second Barons' War, the city's archa was burned and the Jewish community was violently attacked. There was another attack in 1275, but without fatalities. The community was expelled with the rest of England's Jews in 1290. There is a surviving Jewish ritual bath, from this time period now known as Jacob's Well. First interpreted as a mikveh, this was subsequently re-evaluated as a Bet Tohorah, associated with the nearby Jewish cemetery at Jews Acre.
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=== Guidelines === American Association of Blood Banks Clinical Practice Guidelines Australian National Blood Authority Patient Blood Management Guidelines British Committee for Standards in Haematology National Institute for Health and Care Excellence Blood Transfusion Guidance UK Guidance for transfusion. Canadian Blood Transfusion Guidelines German Medical Association Guidelines (English) Archived 2022-04-01 at the Wayback Machine, published 2014.
Sources: en.wikipedia.org
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.
No. It is a laboratory-made analog of growth hormone-releasing hormone. The natural hormone is a 44-residue peptide, while the analog is built on a shorter 29-residue fragment.