This is a working overview of tetrapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-12-20 and is reviewed periodically as new material appears.
The compound is described in the literature as a derivative of epithalamin, a preparation obtained from bovine pineal tissue. Work on this peptide family was carried out mainly by a research group in Saint Petersburg beginning in the 1980s, and the substance was later registered for clinical use in Russia under the name Epitalon. Outside that region it is generally treated as a research chemical rather than an approved medicine. Statements about its biological activity rest on a relatively small number of studies, and independent replication remains limited.
In its supplied form epitalon is a white to off-white powder, usually lyophilized and often hygroscopic. It dissolves readily in water and in aqueous buffers, and it is commonly handled as the acetate or trifluoroacetate salt to improve stability during purification and drying. The amide backbone is labile in aqueous media, so solutions are less durable than the dry solid. Handling notes in the chemical literature therefore emphasize keeping the powder dry, cool and shielded from light until it is dissolved.
Purity assessment of peptide reagents normally relies on reversed-phase high-performance liquid chromatography. A gradient of acetonitrile in water with trifluoroacetic acid, paired with a C18 stationary phase, separates the target tetrapeptide from truncated sequences and deletion analogues. Detection at 214 nanometres exploits absorbance of the peptide backbone, since the molecule contains no aromatic residue. Results are expressed as a percentage of total peak area. Values above ninety-five percent are typical for research-grade material, although reporting conventions vary between suppliers.
Identity confirmation uses mass spectrometry, usually electrospray ionisation in positive mode or matrix-assisted laser desorption. The protonated free peptide produces a signal near three hundred and ninety-one daltons, while salt adducts shift that value slightly. Tandem mass spectrometry or amino acid analysis supplies sequence-level confirmation, which a single mass measurement cannot. Peptides containing aspartate can cyclise into succinimide intermediates that hydrolyse to isoaspartate isomers of identical mass. Because those isomers are difficult to separate chromatographically, identity and purity results carry more weight when interpreted together.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic tetrapeptide | Four residues, linear chain |
| Residue sequence | Ala-Glu-Asp-Gly | Single-letter form AEDG |
| Calculated mass | 390.3 daltons | Value for the free, uncharged form |
| Appearance | White to off-white powder | Usually supplied lyophilized |
| Solubility | Freely soluble in water | Often handled as a salt form |
Several names circulate for the same molecule, including epitalon, epithalone, epithalamin tetrapeptide, and the sequence code AEDG. A CAS registry number, 307297-39-8, is commonly cited for it, though catalogue entries should be checked against supplier documentation because mislabelled records occur. In its usual form the peptide carries free amino and carboxyl termini and is neither glycosylated nor lipidated. Researchers distinguish the defined tetrapeptide from epithalamin itself, a crude pineal preparation containing many peptides that is not chemically characterised.
Material supplied for laboratory use is normally a lyophilised white to off-white powder that dissolves readily in water and in isotonic saline. Lyophilised cakes are hygroscopic and should be equilibrated to room temperature before opening to limit condensation on the solid. Solutions are typically prepared at milligram-per-millilitre concentrations and divided into single-use aliquots, because repeated freeze–thaw cycles degrade short peptides. Aqueous solutions are far less stable than the dry powder, and identity is usually verified by mass spectrometry alongside purity estimation from reversed-phase high-performance liquid chromatography.
Identity is normally established by reversed-phase high-performance liquid chromatography combined with mass spectrometry, a pairing that separates components and confirms molecular mass at once. Purity is quoted as a percentage from the chromatogram, and figures above ninety-five percent are a frequent commercial specification. Amino acid analysis or sequencing supplies further confirmation when required. Because many short peptides behave similarly under chromatography, retention time alone does not establish sequence; the mass measurement is what separates one tetrapeptide from another, and certificates should report both.
Short peptides such as AEDG are normally supplied as a freeze-dried solid and are kept dry, cold, and shielded from light. Holding at minus twenty degrees Celsius is common for the long term, while a refrigerator suffices for brief periods before use. The material takes up moisture to some degree, so containers should stay sealed and be allowed to reach room temperature before opening, which limits condensation on the contents. Repeated warming and cooling of a single container is discouraged because it admits water and can lower the amount of intact peptide.
The peptide is a synthetic analogue of epithalamin, a preparation extracted from bovine pineal glands. Investigators sought a short, chemically defined molecule that would reproduce some of the endocrine and gerontological observations attributed to the glandular extract. Proposed mechanisms centre on induction of telomerase activity, an effect reported in cultured human somatic cells in the early 2000s, together with influences on melatonin secretion and neuroendocrine regulation. Those mechanisms remain incompletely characterised, and the reported telomerase response has not been consistently reproduced by independent groups working in comparable systems.
Published work on this compound consists mainly of in vitro experiments, animal studies, and small clinical investigations, a substantial share of which appeared in Russian-language journals. Sample sizes are generally small, control conditions differ between studies, and several endpoints rely on markers whose clinical meaning is itself debated. Reviews of the longevity field treat the peptide as an early example of telomerase-directed research rather than an established intervention. Regulatory treatment varies by country: some jurisdictions place it under prescription controls, others treat it as a laboratory material, and importation may be restricted regardless of local status.
Procollagen-proline dioxygenase, commonly known as prolyl hydroxylase, is a member of the class of enzymes known as alpha-ketoglutarate-dependent hydroxylases. These enzymes catalyze the incorporation of oxygen into organic substrates through a mechanism that requires α-ketoglutaric acid, Fe2+, and ascorbate. This particular enzyme catalyzes the formation of (2S, 4R)-4-hydroxyproline, a compound that represents the most prevalent post-translational modification in the human proteome.
Different amino-acid sequences have different propensities for forming α-helical structure. Alanine, uncharged glutamate, leucine, charged arginine, methionine and charged lysine have especially high helix-forming propensities, whereas proline and glycine have poor helix-forming propensities. Proline either breaks or kinks a helix, both because it cannot donate an amide hydrogen bond (because it has none) and because its sidechain interferes sterically with the backbone of the preceding turn – inside a helix, which forces a bend of about 30° in the helix's axis. However, proline is often the first residue of a helix, presumably due to its structural rigidity. At the other extreme, glycine also tends to disrupt helices because its high conformational flexibility makes it entropically expensive to adopt the relatively constrained α-helical structure.
Chemical antagonism occurs when a chemical antagonist combines with a ligand to form an inactive product compound, inhibiting the response. In chemical antagonism, the receptors are not involved in the process, and the antagonist directly binds with or removes the ligand. It prevents the ligand from binding to the receptor. As the ligand cannot stimulate the receptor, no physiological effect is generated by the receptors and thus provides an inhibitory effect. The common types of chemical antagonism include chelating agents, neutralising antibodies and salt aggregation.
Trials to assess the effectiveness of an immunity passport scheme, also known as a COVID passport or COVID certification scheme, were confirmed by the UK government on 3 April 2021 as a way of helping to restart public events in England during the COVID-19 pandemic. The announcement was made following much discussion and speculation about the idea by politicians and in the British media. The government announced that trials of a scheme for England would begin on 16 April, starting with a comedy evening in Liverpool. In December 2021, COVID passports or similar verification methods became mandatory to access certain high-density venues per government regulations to address the spread of the infections Omicron variant of COVID-19.
The PTB2 RNA motif is a conserved intronic RNA element identified in plant homologs of the polypyrimidine tract-binding protein 2 (PTB2) gene that has been reported as a cis-regulatory element. PTB2 is an RNA motif reported as a stem-loop structure, with the loop containing a conserved GUGUGU sequence that encompasses the 5′ splice site of a cassette exon involved in alternative splicing. The 3' side of the stem contains a long conserved pyrimidine-rich tract. The PTB2 RNA motif was identified in homologous of 93 species of Pentapetalae plants. The long conserved pyrimidine-rich tract located on the 3′ side of the PTB2 RNA motif stem suggests a role in regulation of PTB2 genes. The co-occurrence of the PTB2 RNA motif and PTB2 genes is consistent with a mechanistic link between RNA secondary structure and PTB-mediated splicing regulation. The motif has been proposed to contribute to regulation of PTB2 expression by influencing PTB1/PTB2 binding and promoting cassette exon inclusion during alternative splicing, which can lead to nonsense-mediated decay of the resulting transcript.
Sources: en.wikipedia.org
Digestion of complex carbohydrates allows glucose molecules to be re-polymerized into a form that is recognized by enzymes. In mammals, glucose molecules polymerize into glycogen stores or glycogenin. The reformation of carbohydrates is essential for converting them into forms that can be more easily transported to cells with higher glucose requirements. Both mammals and plants use the same mechanisms to convert glucose into complex carbohydrates; the only difference is the enzymes used to catalyze the mechanisms. Mammals require glycogen synthase and glycogenin to synthesize glycogen. Plants synthesize amylose with starch synthase and amylopectin with starch-branching enzymes.
The element was named after Marie Curie and her husband Pierre Curie, who are known for discovering radium and for their work in radioactivity. It followed the example of gadolinium, a lanthanide element above curium in the periodic table, which was named after the explorer of rare-earth elements Johan Gadolin:
=== Avoiding bites === Rattlesnakes tend to avoid wide-open spaces where they cannot hide from predators, and generally avoid humans if they are aware of their approach. Rattlesnakes rarely bite unless they feel threatened or provoked. A majority of victims (about 72%) are males. Around half of bites occur in cases where the victim saw the snake, yet made no effort to move away. Harassing or attacking a rattlesnake, illegal in some jurisdictions, puts one at much higher risk of a bite. Rattlesnakes seek to avoid humans and other predators or large herbivores that themselves pose lethal danger. Dogs, often much more aggressive than humans, are much more likely to experience a snakebite, and are more likely to die of a rattlesnake bite although they can be vaccinated against them. Caution is advised even when snakes are believed to be dead; rattlesnake heads can sense, flick the tongue, and inflict venomous bites reflexively for up to an hour after being severed from the body.
In the ensuing power struggle for control over the province, General Wang Zuanxu made a deal with Liu that he would return the Ya'an and Xichang regions to Xikang as well as subsidize the Xikang government with 360,000 yuan per year in exchange for Liu's support. This deal went through, and the central government even agreed to fund a highway from Sichuan to Xikang. On 28 November, 1938, the Executive Yuan ratified the establishment of Xikang Province, which was officially inaugurated on 1 January, 1939. Liu Wenhui became the governor of Xikang. In exchange, Wang Zuanxu was able to become the acting chairman of Sichuan Province, although he failed to secure control and was later usurped by Chiang Kai-shek himself. Liu Wenhui's provincial government was highly nepotistic, made up mostly of personal connections, secretaries, and subordinate officers. Only one politician in the new government, Ye Xiufeng, was a Chiang loyalist: he was subsequently outmaneuvered by Liu and dismissed within two years. Although the Tibetan population were hopeful that the establishment of the province would entail increased representation, Liu only appointed one Tibetan, a monk, to the governing board. This was justified by the national government as a prioritization of national stability over minority rights, ensuring that the Xikang government remained Han-centric and Han-dominant. In addition, the wartime situation meant that by cooperating with the central government, Liu Wenhui would be able to maintain his rule over Xikang.
Sources: en.wikipedia.org
As with all catalysts, enzymes do not alter the position of the chemical equilibrium of the reaction. In the presence of an enzyme, the reaction runs in the same direction as it would without the enzyme, just more quickly. For example, carbonic anhydrase catalyzes its reaction in either direction depending on the concentration of its reactants:
Soft tissue is tissue in the body that connects and surrounds or supports internal organs and bones, and includes muscle, tendons, ligaments, fat, fibrous tissue, lymph and blood vessels, fasciae, and synovial membranes. Soft tissue is not hardened by the processes of ossification or calcification such as bones and teeth. It is sometimes defined by what it is not – such as "nonepithelial, extraskeletal mesenchyme exclusive of the reticuloendothelial system and glia".
Most animals rely on biomass and bioenergy produced by plants and phytoplanktons (collectively called producers) through photosynthesis. Herbivores, as primary consumers, eat the plant material directly to digest and absorb the nutrients, while carnivores and other animals on higher trophic levels indirectly acquire the nutrients by eating the herbivores or other animals that have eaten the herbivores. Animals oxidise carbohydrates, lipids, proteins and other biomolecules in cellular respiration, which allows the animal to grow and to sustain basal metabolism and fuel other biological processes such as locomotion. Of the 550 gigatons of carbon biomass on Earth, animals account for 2 gigatons. Some benthic animals living close to hydrothermal vents and cold seeps on the dark sea floor consume organic matter produced through chemosynthesis (via oxidising inorganic compounds such as hydrogen sulfide) by archaea and bacteria. Animals originated in the ocean; all extant animal phyla, except for Micrognathozoa and Onychophora, feature at least some marine species. However, several lineages of arthropods begun to colonise land around the same time as land plants, between 510 and 471 million years ago, during the Late Cambrian or Early Ordovician periods. Vertebrates such as the lobe-finned fish Tiktaalik started to move on to land in the late Devonian, about 375 million years ago.
== Medical uses == Allogeneic cultured keratinocytes and fibroblasts in bovine collagen is indicated for topical (non-submerged) application to a surgically created vascular wound bed in the treatment of mucogingival conditions in adults.
=== Alkali disease === However, the incorporation of selenomethionine into tissue proteins and keratin in cattle, birds, and fish causes alkali disease. Alkali disease is characterized by emaciation, loss of hair, deformation and shedding of hooves, loss of vitality, and erosion of the joints of long bones.
Sources: en.wikipedia.org
The peptide contains four residues in the order alanine, glutamate, aspartate and glycine, abbreviated AEDG. The chain is linear and held together by three peptide bonds. Its calculated mass for the uncharged free form is about 390.3 daltons.
Epithalamin refers to a crude preparation derived from bovine pineal tissue, which contains many components. Epitalon is a single synthetic tetrapeptide identified from that material and produced by chemical synthesis. The two names are sometimes confused because early reports treated the synthetic peptide as an active fragment of the extract.
It has been registered for clinical use in Russia, where it is associated with a small family of short peptides. In most other jurisdictions it is not an approved medicine and is traded as a research chemical. Regulatory status varies by country and changes over time.
Reversed-phase high-performance liquid chromatography with ultraviolet detection at 214 nanometres is the usual approach. Peak area percentage provides a purity figure relative to other components in the sample. Mass spectrometry is then applied to confirm identity.