Tetrapeptide 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 2025-10-31. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
Epitalon is a synthetic linear tetrapeptide with the sequence alanine–glutamate–aspartate–glycine, abbreviated AEDG. Its molecular formula is C14H22N4O9 and the calculated mass is approximately 390.35 g/mol. The compound is made by solid-phase peptide synthesis rather than extracted from tissue, although early work described it as a short fragment of a peptide fraction obtained from bovine pineal extract. In the research literature the spelling epitalon and the variant epithalone both appear, while AEDG is the standard code used in peptide nomenclature.
| 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 |
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.
Residue composition is the property that most cleanly separates verified material from mislabelled samples. Alanine, glutamate, aspartate and glycine appear in that order from the N-terminus, and the two acidic residues sit in the middle of the chain. Because the peptide is short, it can be produced by solid-phase synthesis and characterised by mass spectrometry without ambiguity. Any reported sample whose measured mass departs substantially from 390 daltons is a different compound or a degraded mixture rather than epitalon.
Epitalon is a synthetic tetrapeptide whose four residues are alanine, glutamate, aspartate and glycine, commonly abbreviated AEDG. Its molecular formula is C14H22N4O9 and its monoisotopic mass is near 390.35 daltons. The peptide carries two acidic side chains, so it is neutral to negatively charged in most aqueous buffers. Published reference summaries usually list it under both spellings, epitalon and epithalon, and treat the two names as the same material.
=== Shark repellent === P. marmoratas and P. pavoninus release pardaxin when threatened by sharks. Pardaxin targets the gills and pharyngeal cavity of the sharks. It results in severe struggling, mouth paralysis, and temporary increase of urea leakage in the gills. This distress is caused by the attack of the cellular membrane of the gills, which causes a large influx of salt ions. Research into creating a commercial shark repellent using pardaxin was discontinued because it dilutes in the water too quickly. It is only effective if sprayed almost directly into a shark's mouth.
=== Metabolism === While other opioids in its class, such as codeine or oxycodone, are metabolized via CYP450 enzymes, hydromorphone is not. Hydromorphone is extensively metabolized in the liver to hydromorphone-3-glucuronide, which has no analgesic effects. As similarly seen with the morphine metabolite, morphine-3-glucuronide, a build-up in levels of hydromorphone-3-glucuronide may produce excitatory neurotoxic effects such as restlessness, myoclonus and hyperalgesia. Patients with compromised kidney function and older patients are at higher risk for metabolite accumulation.
==== Oral testosterone ==== Testosterone is well-absorbed but extensively metabolized with oral administration due to the first pass through the intestines and liver. It is rapidly and completely inactivated in men at doses of less than 200 mg. In large doses, such as 200 mg however, significant increases in circulating testosterone levels become apparent. In addition, while a 60 mg dose has no effect on testosterone levels in men, this dose does measurably increase testosterone levels in prepubertal boys and women. The oral bioavailability of testosterone in young women after a single 25 mg dose was found to be 3.6 ± 2.5%. High levels of testosterone are also achieved with a 60 mg dose of oral testosterone in men with liver cirrhosis. These findings are attributed to induction of liver enzymes by testosterone and consequent activation of its own metabolism. Substitution dosages of oral testosterone in men are in the range of 400 to 800 mg/day. Such doses exceed the amount of testosterone produced by the body, which is approximately 7 mg/day, by approximately 100-fold. The elimination half-life of oral testosterone is rapid at about 5 to 7 hours. As a result, it requires administration several times per day in divided doses. Due to its limitations, such as the high doses required and necessity of multiple daily doses, oral testosterone is not used clinically in its unmodified form. Oral testosterone has been studied in combination with a 5α-reductase inhibitor to reduce its first-pass metabolism and improve its bioavailability.
The hydroxide ion OH−, a well known base, is here acting as the conjugate base of the acid water. Acids and bases are thus regarded simply as donors and acceptors of protons respectively. A broader definition of acid dissociation includes hydrolysis, in which protons are produced by the splitting of water molecules. For example, boric acid (B(OH)3) produces H3O+ as if it were a proton donor, but it has been confirmed by Raman spectroscopy that this is due to the hydrolysis equilibrium:
The subject is required to touch his or her nose with eyes closed; people with normal proprioception may make an error of no more than 20 mm (0.79 in), while people with impaired proprioception (a symptom of moderate to severe alcohol intoxication) fail this test due to difficulty locating their limbs in space relative to their noses.
Sources: en.wikipedia.org
In general, adsorption increases with decreasing temperature and increasing pressure (until a maximum is reached, typically 20–30 bar, after which the adsorption capacity decreases). However, MOFs to be used for hydrogen storage in automotive fuel cells need to operate efficiently at ambient temperature and pressures between 1 and 100 bar, as these are the values that are deemed safe for automotive applications.
The dominant narrative in the American Masonic histories for decades related that it was these American Freemasons who allowed Freemasonry to resurge in Cuba, but several modern historians write that it was the Cubans themselves who forced the resurgence, and the change in their government's approach to the nature of Freemasonry allowed them a sense of autonomy, rather than a complete dominance. Revolutionary GOCA exiles were allowed to return to the island, including its founder Aurelio Miranda y Álvarez, and Fernando Figueredo Socarrás. They met with Cuban Freemasons who had fought for independence in Cuba, such as José Fernández Pellón, Francisco de Paula Rodríguez, Gerardo L. Betancourt, Juan Bautista Hernández Barreiro, and Miguel Gener. When Governor Brooke officially assumed office, Miguel Gener, the Grand Commander of the Supreme Council, offered his respects to the General, and committed to cooperation with the North American bodies of Freemasonry. Soon after this, Gener was appointed to the office of Mayor of Havana. Freemasonry was "officially" reestablished in Cuba on February 5, 1899, when the Supreme Council of Colon and the Island of Cuba was reformed to become the Supreme Council of Cuba, which is the same Supreme Council that exists today. The United Grand Lodge of Colon and the Island of Cuba was reformed on March 26 to become the Grande Lodge of Cuba, at the same industrial property now owned by Padilla Lodge. Juan Bautista Hernández Barreiro was elected Grand Master, who simultaneously served as the government's Minister of Public Instruction.
In Australia, specialist training is undertaken as a registrar; The term 'resident' is used synonymously with 'hospital medical officer' (HMO), and refers to unspecialised postgraduate medical practitioners prior to specialty training. Entry into a specialist training program occurs after completing one year as an intern (post-graduate year 1 or "PGY1"), then, for many training programs, an additional year as a resident (PGY2 onward). Training lengths can range from 3 years for general practice to 7 years for paediatric surgery.
=== 1. Ideality === In June 2010, Baran authored a paper describing the "Ideal Synthesis" in which he presents a simple and informative definition of "ideality" when comparing molecular syntheses. Building off of ideas discussed by James B. Hendrickson in 1975, "ideality" refers to the concept of making molecules in a way that minimizes concession steps (e.g. adding/removing protecting groups) and maximizes construction steps (i.e. C-C or C-heteroatom bond forming and strategic redox steps). Importantly, this conversation of synthetic ideality is limited to comparisons of syntheses of the same molecule.
Sources: en.wikipedia.org
== Function == Gamma-glutamyltransferase is a membrane-associated protein involved in both glutathione metabolism and the transpeptidation of amino acids. Changes in gamma-glutamyltransferase activity may signal preneoplastic or toxic conditions in the liver or kidney. The protein encoded by this gene is similar in sequence to gamma-glutamyltransferase, but its function is unknown.
Large quantities of both adenoviruses are produced by HEK 293 cells that have the E1 gene necessary for viral replication. Rarely, Ad5 can acquire the E1 gene from the HEK 293 cells, restoring its ability to replicate. Gamaleya has set an acceptable limit of 5,000 replicating virus particles per vaccine dose, and quality control documents state that tested batches contain less than 100 replicating virus particles per dose. The production of the frozen liquid formulation was developed for large-scale use, it is cheaper and easier to manufacture. The production of the freeze-dried formulation takes much more time and resources, although it is more convenient for storage and transportation. It was developed with vaccine delivery to hard-to-reach regions of Russia in mind. According to Russian media, the mass production of the Gam-COVID-Vac was launched by 15 August. By that moment, the Russian Federation has already received applications from 20 countries for the supply of 1 billion doses of vaccine. Three facilities were able to produce about a million doses per month at each with a potential doubling of capacity by winter. By the end of 2020, Gamaleya Research Institute's production, according to an interview with the organization's spokesperson, was planned to produce 3–5 million doses. As of March 2021, the Russian Direct Investment Fund (RDIF) has licensed production in India, China, South Korea and Brazil. In the EU, RDIF has signed production agreements.
=== Impact on negotiations of extraditing suspects to Singapore === In 2002, Singapore tried to negotiate with Australia for the extradition of a British murder suspect and fugitive Michael McCrea, who was wanted for the double murder of a couple whose corpses were discovered abandoned in a car at Orchard Towers. However, McCrea, who was arrested in Australia, was not extradited as Australia, which abolished the death penalty for all offences by then, was not legally allowed to extradite suspects back to countries where they would face the death sentence. It was only after Singapore gave the Australian government the assurance that McCrea would not be hanged even if he was convicted of murder, which allowed McCrea to be sent back to Singapore for trial. McCrea was eventually convicted of culpable homicide and destroying evidence of a murder case, and sentenced to a total of 24 years in jail. This left an impact and precedent on Singapore's avenues to successfully negotiating for extradition of suspects from countries where the death penalty or caning was not practised, including the extradition of suspected bank robber David James Roach, whom the Singapore government promised would not face caning for robbery. Roach was eventually sent back to Singapore, where he later served five years in prison, and he was pardoned from caning by President Halimah Yacob.
== Policy and advocacy == As the pre-eminent body representing human genetics in Oceania, the HGSA authors numerous policies and position statements to guide practitioners in the region. Such documents cover diverse topics such as genomic testing; screening for genetic disorders; ethical practice in genomics; genetic education; and clinical service delivery. In addition, the HGSA actively comments on policy and guidelines authored by other institutions and provides expert advice to government and genomic regulatory authorities.
=== Support groups === People affected by amyloidosis are supported by organizations, including the Amyloidosis Research Consortium, Amyloidosis Foundation, Amyloidosis Support Groups, and Australian Amyloidosis Network.
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.
It is a synthetic tetrapeptide. Its sequence was derived from research on peptide fractions of bovine pineal extract, and the intact AEDG sequence has not been demonstrated as an abundant free peptide in human tissue.