A practical reference on DAC group: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-10-04 and is reviewed periodically as new material appears.
CJC-1295 is the name used for a synthetic peptide modeled on growth hormone-releasing hormone, the hypothalamic signal that prompts the pituitary to release growth hormone. The compound was described by a Canadian drug discovery company in the mid-2000s as a long-acting research tool. Two closely related molecules share the name in practice: one carries a drug affinity complex, or DAC, group, and one does not. The distinction matters because the two behave differently 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.
The peptide binds GHRH receptors on somatotroph cells within the anterior pituitary, triggering a signalling cascade that increases growth hormone secretion. Its improved resistance to dipeptidyl peptidase IV degradation distinguishes it from the parent hormone. In the DAC-bearing version, a maleimide group reacts with a cysteine residue on serum albumin, forming a covalent bond that keeps the peptide in circulation far longer. That albumin attachment is the central design feature separating the two research variants.
Pharmacokinetic behaviour differs sharply between the two forms. The DAC-bearing peptide shows an extended circulation time measured in days, whereas the version without the complex is cleared within roughly half an hour. This gap shapes how researchers design dosing schedules in animal models. Whether the prolonged presence of the DAC form produces effects meaningfully different from the short-acting variant remains an open question, since comparative human data are scarce.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic peptide | GHRH analog, not a steroid |
| Backbone length | 29 amino acids | Based on GRF(1-29) |
| Substitutions | Four positions | D-Ala2, Gln8, Ala15, Leu27 |
| Appearance | White to off-white powder | Typical lyophilized research material |
| Common synonyms | Modified GRF(1-29) | Usage varies between sources |
Purity is most often assessed by reversed-phase high-performance liquid chromatography, reported as a percentage of total peak area. Identity is confirmed by mass spectrometry, which yields a molecular ion consistent with the expected sequence. Amino acid analysis and peptide mapping provide additional characterization. Reported purity values are method-dependent, so figures from different laboratories are not always directly comparable without details of column, gradient, and detection wavelength.
Peptide degradation proceeds mainly through hydrolysis, oxidation of methionine, and deamidation of asparagine or glutamine residues. The maleimide group on the albumin-binding variant can also react with thiols or hydrolyze in aqueous media. Because these pathways accelerate with temperature and pH extremes, handling conditions strongly influence measured stability. Stability data in the public literature are limited and often generated under differing conditions, so general statements about shelf life should be read as approximate.
Research material is normally supplied as a freeze-dried powder in sealed vials. In that state the peptide is comparatively robust, but prolonged exposure to warmth, moisture, or light accelerates degradation. Storage at minus twenty degrees Celsius or lower, with desiccant and protection from light, is the commonly described practice. Vials should be allowed to reach room temperature before opening to limit condensation on the powder. Moisture uptake during handling is a recognized source of variability in later measurements.
The two variants differ dramatically in how long they persist in circulation. The form lacking the albumin-binding group has a plasma half-life measured in tens of minutes, comparable to the natural hormone fragment. The version carrying the drug affinity complex binds albumin and shows a half-life of roughly six to eight days in human studies. That figure comes from small trials that tracked hormone levels over extended periods. The physiological consequences of sustained versus pulsatile stimulation are still debated and the literature does not settle the point.
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.
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.
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=== Cationic ERLIC === A negatively charged cation exchange column can be used for ERLIC separations to reduce the influence of anionic (negatively charged) groups on analyte retention. For example, reducing the influence the phosphates of nucleotides or of phosphonyl antibiotic mixtures; or sialic acid groups of modified carbohydrates, to allow separation based more on the basic and/or neutral functional groups of these molecules. Modifying the polarity of a weakly ionic group (e.g. carboxyl) on the surface is easily accomplished by adjusting the pH to be within two pH units of that group's pKa. For strongly ionic functional groups of the surface (i.e. sulfates or phosphates), lower amount of buffer can be used so the residual charge is not completely ion paired. An example of this would be the use of a 12.5mM (rather than the recommended >20mM buffer), pH 9.2 mobile phase on a polymeric, zwitterionic, betaine-sulfonate surface to separate phosphonyl antibiotic mixtures (each containing a phosphate group). This enhances the influence of the column's sulfonic acid functional groups over its surface chemistry, slightly diminished (by pH), quaternary amine. These analytes will show a reduced retention on the column eluting earlier, and in higher amounts of organic solvent, than if a neutral polar HILIC surface were used. This also increases their detection sensitivity by negative ion mass spectrometry.
The ancestors of bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life. Although bacterial fossils exist, such as stromatolites, their lack of distinctive morphology prevents them from being used to examine the history of bacterial evolution, or to date the time of origin of a particular bacterial species. However, gene sequences can be used to reconstruct the bacterial phylogeny, and these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. The most recent common ancestor (MRCA) of bacteria and archaea was probably a hyperthermophile that lived about 2.5 billion–3.2 billion years ago. The earliest life on land may have been bacteria some 3.22 billion years ago. Bacteria were also involved in the second great evolutionary divergence, that of the archaea and eukaryotes. Here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea. This involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes, which are still found in all known Eukarya (sometimes in highly reduced form, e.g. in species of amitochondrial protozoa).
and Mw is the molecular mass. This plot acts as a calibration curve, which is used to approximate the desired compound's molecular weight. The Ve component represents the volume at which the intermediate molecules elute such as molecules that have partial access to the beads of the column. In addition, Vt is the sum of the total volume between the beads and the volume within the beads. The Vo component represents the volume at which the larger molecules elute, which elute in the beginning. Disadvantages are, for example, that only a limited number of bands can be accommodated because the time scale of the chromatogram is short, and, in general, there must be a 10% difference in molecular mass to have a good resolution.
Sources: en.wikipedia.org
The molar mass M(X) of a compound is given by the sum of the relative atomic masses Ar(Xi) of the elements (each multiplied by the number of atoms ni per element) which form the compound multiplied by the molar mass constant, Mu ≈ 1 g/mol:
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S. affinis is planted as a bulb (vegetative) in spring (March–May). Multiple bulbs are planted 5 to 8 cm (2 to 3+1⁄8 in) deep into a hole of dimensions 30 by 30 cm (12 by 12 in). The plant can achieve a height of 30 cm (12 in). Weeding is necessary but it is important not to damage the root system. A sufficient water supply during summer is important. Harvest is from November to March. It is important that the soil is not frozen when harvesting. The storage of S. affinis tubers is difficult. Because of their thin skin, they can be stored only for a few days, about a week in a fridge. An alternative can be a fresh ongoing harvesting out of humid sand, thereby the tubers stay fresh for several months.
Sources: en.wikipedia.org
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.
The original material included a linker that binds serum albumin. A later variant removed that linker to reduce the duration of action. Catalogs and papers did not consistently adopt separate names, so both remain widely labeled with the same term.
The amino acid sequence and the presence or absence of the linker group. Mass measured by spectrometry gives an independent check that separates the two forms.
The synthetic peptide keeps the receptor-binding region of GHRH but carries substitutions that resist enzymatic cleavage. In the DAC version, an added group also anchors the molecule to albumin, extending its presence in the bloodstream.