DAC linker is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-01-28. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular weight, DAC form | About 3647 Da | Varies with salt form |
| Molecular weight, non-DAC form | About 3358 Da | MOD GRF(1-29) |
| Solubility class | Water soluble | Also dissolves in polar solvents |
| Reported half-life, DAC form | About five to eight days | Values from human studies |
| Common synonyms | CJC-1295; MOD GRF(1-29) | Name depends on variant |
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.
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.
Two forms circulate under the CJC-1295 name, and they differ by a single appended group. The version without a drug affinity complex carries four substitutions along the peptide chain, including a D-alanine near the amino terminus and replacements at three other positions. These changes block the enzyme dipeptidyl peptidase IV and remove a methionine residue that is prone to oxidation. The modified fragment is frequently labeled MOD GRF 1-29. Naming conventions are inconsistent across informal sources, which is a common source of confusion.
The second form adds a maleimide-bearing linker to the lysine at the carboxyl end. This group reacts with cysteine-34 on circulating serum albumin, forming a covalent bond that keeps the peptide in the bloodstream for far longer. ConjuChem developed the molecule as a way to extend the action of a peptide without frequent administration. The albumin attachment is the defining structural feature of the drug affinity complex version. Whether continuous exposure produces effects distinct from shorter pulses remains an unresolved research question.
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Notably, targeted proteomics shows increased reproducibility and repeatability compared with shotgun methods, although at the expense of data density and effectiveness. Data quality. Proteomic analysis is highly amenable to automation and large data sets are created, which are processed by software algorithms. Filter parameters are used to reduce the number of false hits, but they cannot be eliminated. Scientists have expressed the need for awareness that proteomics experiments should adhere to the criteria of analytical chemistry (sufficient data quality, sanity check, validation).
Sources: en.wikipedia.org
Tertiary structure refers to the three-dimensional structure created by a single protein molecule (a single polypeptide chain). It may include one or several domains. The α-helices and β-pleated-sheets are folded into a compact globular structure. The folding is driven by the non-specific hydrophobic interactions, the burial of hydrophobic residues from water, but the structure is stable only when the parts of a protein domain are locked into place by specific tertiary interactions, such as salt bridges, hydrogen bonds, and the tight packing of side chains and disulfide bonds. The disulfide bonds are extremely rare in cytosolic proteins, since the cytosol (intracellular fluid) is generally a reducing environment.
== External links == glycosciences.de This site provides databases and bioinformatics tools for glycobiology and glycomics. GlycomeDB, A carbohydrate structure metadatabase GlycoBase A web HPLC/UPLC resource that contains elution positions expressed as glucose unit values. ProGlycAn A short introduction to glycan analysis and a nomenclature for N-Glycans Emanual Maverakis; et al. "Glycans in the immune system and The Altered Glycan Theory of Autoimmunity" (PDF). CD BioGlyco This site provides database and tools in the field of glycomics, from glycan release, separation, and purification, glycan derivatization to glycan characterization and quantification.
== History == With the capture of Óscar Orlando Nava Valencia in October 2009 and the death of Ignacio Coronel Villarreal, of the Sinaloa Cartel in 29 July 2010, a power vacuum emerged and the Milenio Cartel (then loyal to the Sinaloa Cartel) broke into smaller factions. The most notable were the Jalisco New Generation Cartel (CJNG) headed by Nemesio Oseguera Cervantes "El Mencho" (who suspected the Sinaloa cartel had betrayed its leaders) and La Resistencia headed by Ramiro Pozos "El Molca" who switched alliances to form a brief alliance with Los Zetas (La Resistencia was founded by Sinaloa to counter Los Zetas), and started a turf war for control of the region. Some members of the Milenio Cartel, then a Sinaloa Cartel branch, who splintered and formed the CJNG were Nemesio Oseguera Cervantes (El Mencho), Érick Valencia Salazar (El 85) and Martín Arzola Ortega (El 53). With this split, a turf war against La Resistencia, headed by Ramiro Pozos (El Molca), and Los Zetas for the control of the region started. Emilio Alejandro Pulido Saldaña, better known as "El Tiburón", was considered to be a co-founder as well.
Sources: en.wikipedia.org
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The work published by Banting, Best, Collip and Macleod represented the preparation of purified insulin extract suitable for use on human patients. Although Paulescu discovered the principles of the treatment, his saline extract could not be used on humans; he was not mentioned in the 1923 Nobel Prize. Ian Murray was particularly active in working to correct "the historical wrong" against Nicolae Paulescu. Murray was a professor of physiology at the Anderson College of Medicine in Glasgow, United Kingdom, the head of the department of Metabolic Diseases at a leading Glasgow hospital, vice-president of the British Association of Diabetes, and a founding member of the International Diabetes Federation. Murray wrote:
=== Pharmacokinetics === In the field of pharmacokinetics, steady state refers to the condition in which the rate of drug administration is balanced by the rate of drug elimination, resulting in a stable concentration of the drug in the bloodstream over time. This equilibrium typically occurs following repeated dosing or continuous infusion, and is used to ensure consistent therapeutic drug levels. For most drugs exhibiting first-order kinetics, steady state is generally achieved after approximately four to five half-lives, at which point the changes in plasma concentrations between doses become minimal and predictable. At steady state, drug concentrations do not remain at a single, unchanging value but rather fluctuate within a limited range bounded by peak (Cmax) and trough (Cmin) values across each dosing interval. Ideally, this range is maintained above the minimum effective (therapeutic) concentration and below the threshold for adverse effects, thereby achieving concentrations within the so-called therapeutic window.
Sources: en.wikipedia.org
It is a synthetic peptide modeled on growth hormone-releasing hormone. The molecule is used in research on pituitary growth hormone secretion. It differs from the natural hormone through several stabilizing substitutions.
The DAC form carries a maleimide group that binds albumin and extends circulation time. The non-DAC form lacks this group and clears much faster. Both share the same receptor-binding core.
It targets the growth hormone-releasing hormone receptor on pituitary somatotroph cells. Activation raises cyclic AMP and promotes growth hormone release. Normal feedback pathways remain part of the response.
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.