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 2026-04-26 and is reviewed periodically as new material appears.
Epitalon is the common name for a synthetic tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, usually abbreviated AEDG. All four residues are proteinogenic amino acids, and the free peptide has a calculated mass near 390 grams per mole. Because the chain is short and carries no modifications, it is assembled readily by solid-phase synthesis and is distributed mainly as a freeze-dried solid for laboratory work. Catalogue listings use the spellings epitalon, epithalone, and simply AEDG, and the three refer to the same sequence.
The compound is generally presented as a synthetic fragment of epithalamin, a pineal gland extract investigated in the former Soviet Union from the 1970s onward. Vladimir Khavinson and colleagues in Saint Petersburg developed short peptides modelled on such extracts, and epitalon became the most widely cited of those sequences. Most primary reports appeared in Russian-language journals or in proceedings with limited international circulation. Independent replication in laboratories outside that network remains sparse, and much repeated secondary material traces back to a small number of originating groups.
Solubility is high in water, phosphate-buffered saline and normal saline, a pattern that follows from the two acidic residues in the chain. The peptide dissolves poorly in non-polar solvents such as hexane or chloroform. Stock solutions are often prepared in water first and then diluted into the buffer of interest. Because the molecule is small and hydrophilic, filtration through a low-protein-binding membrane is usually straightforward, and visible particulates are uncommon in freshly made solutions.
Identity and purity are established with reversed-phase high-performance liquid chromatography and mass spectrometry. The chromatogram shows the main peak and any truncated or oxidised by-products, while the mass spectrum confirms the expected 390 dalton mass. Amino acid analysis can corroborate composition when a sample's origin is uncertain. Counterion content, particularly residual trifluoroacetate from purification, is frequently reported alongside purity because it shifts the net mass of the solid.
Reference material is normally supplied as a lyophilised powder in a sealed vial. Product literature typically recommends storage at minus twenty degrees Celsius or colder, protected from light and moisture. Freeze-thaw cycling is usually avoided because repeated condensation can introduce water into the vial. Working solutions are commonly prepared fresh, aliquoted, and kept cold for short periods rather than stored at ambient temperature. Labelling the date of opening helps track how long a vial has been in use.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C14H22N4O9 | Computed for the free acid of Ala-Glu-Asp-Gly |
| Molecular mass | About 390.35 g/mol | Free peptide; salt forms shift the value |
| Appearance | White to off-white solid | Typical of short peptides after freeze-drying |
| Solubility class | Freely soluble in water | Aqueous buffers are also commonly used |
| Common synonyms | Epitalon, epithalone, AEDG | AEDG is the single-letter sequence |
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.
The compound is generally described as a synthetic analogue of a fragment isolated from a pineal gland extract. Researchers associated with the Saint Petersburg Institute of Bioregulation and Gerontology introduced it during the 1980s and 1990s while studying short peptides from animal tissue. The original extract, called epithalamin, is a heterogeneous mixture, whereas epitalon is a single defined sequence. That distinction matters because findings reported for the extract are not automatically findings about the pure tetrapeptide, and claims about broader biological effects remain a separate question from the chemical identity described here.
Material sold for research use varies widely in documented quality. A useful verification package includes a certificate of analysis that states peptide content rather than only net weight, the chromatographic method and column used, and a mass spectrum consistent with the expected mass. Independent testing by a third-party laboratory is occasionally reported. Statements of identity resting only on a supplier label provide little assurance, and the gap between nominal mass and actual peptide content can be substantial once counterions and residual water are counted.
Peptides of this size are generally stable as dry solids but degrade in solution over time. The principal routes are hydrolysis of the peptide backbone and oxidation, with hydrolysis favoured by elevated temperature and extreme pH. Aqueous solutions held at room temperature can show measurable loss of purity within days, while frozen aliquots are considerably more durable. Because the sequence contains neither cysteine nor methionine, oxidation is less of a concern than for many other peptides, but pH control during handling still matters.
Chemically, the molecule consists of four amino acid residues joined by three peptide bonds, with a free N-terminal amino group and a free C-terminal carboxyl group. Its molecular formula is C14H22N4O9, and its monoisotopic mass is approximately 390 daltons. The acidic glutamate and aspartate side chains give the peptide a net negative charge near neutral pH, a property that shapes its chromatographic behaviour and solubility profile. No disulfide bridges or other post-translational modifications are present, so the primary sequence alone defines the structure.
Most experimental work has been carried out in cell culture and animal models. Several reports describe changes in telomerase activity and proliferation in cultured cells, while rodent studies have examined lifespan, melatonin rhythm and reproductive endpoints. Human data remain limited, and much of the published clinical material consists of small trials with incomplete reporting of methods and controls. Whether the cell and animal findings translate into measurable effects in people is an open question, and the mechanistic basis of the reported telomerase changes is not fully established.
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.
Storage practice centres on limiting moisture, oxygen, and repeated temperature cycling. Freeze-dried powder is generally held desiccated at minus twenty degrees Celsius or colder and protected from light. Reconstituted solutions are markedly less stable, and the aspartate-glycine junction is prone to succinimide formation at neutral to mildly alkaline pH. Portioning material into single-use aliquots reduces degradation compared with repeated freeze-thaw cycles. Stability data specific to this tetrapeptide remain scarce, so most handling guidance is extrapolated from general peptide chemistry rather than measured directly.
=== HHV-6 receptor ligand === Mori et al. first identified the gene product gQ1, a glycoprotein unique to HHV-6, and found that it forms a complex with gH and gL glycoproteins. They believed that this heterotrimer complex served as the viral ligand for CD46. Soon thereafter, another glycoprotein named gQ2 was identified and found to be part of the gH/gL/gQ1 ligand complex, forming a heterotetramer that was positively identified as the viral CD46 ligand. The exact process of entry is not yet well understood.
C-value The total amount of DNA contained within a haploid nucleus (e.g. a gamete) of a particular organism or species, expressed in number of base pairs or in units of mass (typically picograms); or, equivalently, one-half the amount in a diploid somatic cell. For simple diploid eukaryotes the term is often used interchangeably with genome size, but in certain cases, e.g. in hybrid polyploids descended from parents of different species, the C-value may actually represent two or more distinct genomes contained within the same nucleus. C-values apply only to genomic DNA, and notably exclude extranuclear DNA.
According to the Encyclopedia Britannica, "the attempt by Salvador Allende to unite Marxists and other reformers in a socialist reconstruction of Chile is most representative of the direction that Latin American socialists have taken since the late 20th century. ... Several socialist (or socialist-leaning) leaders have followed Allende's example in winning election to office in Latin American countries." Venezuelan President Hugo Chávez, Nicaraguan President Daniel Ortega, Bolivian President Evo Morales and Ecuadorian President Rafael Correa refer to their political programmes as socialist and Chávez adopted the term socialism of the 21st century. After winning re-election in December 2006, Chávez stated: "Now more than ever, I am obliged to move Venezuela's path towards socialism." The pink tide is a term used in the 2000s in political analysis in the media and elsewhere to describe the perception that left-wing politics were becoming increasingly influential in Latin America. To network this movement, the Foro de São Paulo is a conference of leftist political parties and other organisations from Latin America and the Caribbean.
Dermatology Neurosurgery Ophthalmology Oral and maxillofacial surgery Orthopedic surgery Otorhinolaryngology Podiatric surgery – do not undergo medical school training, but rather separate training in podiatry school Urology
Sources: en.wikipedia.org
==== Complement Activation ==== The complement system includes blood proteins that can cause cell death after an antibody binds to the cell surface (the classical complement pathway, among the ways of complement activation). Generally, the system deals with foreign pathogens but can be activated with therapeutic antibodies in cancer. The system can be triggered if the antibody is chimeric, humanized, or human; as long as it contains the IgG1 Fc region. Complement can lead to cell death by activation of the membrane attack complex, known as complement-dependent cytotoxicity; enhancement of antibody-dependent cell-mediated cytotoxicity; and CR3-dependent cellular cytotoxicity. Complement-dependent cytotoxicity occurs when antibodies bind to the cancer cell surface, the C1 complex binds to these antibodies and subsequently, protein pores are formed in cancer cell membrane. Blocking Antibody therapies can also function by binding to proteins and physically blocking them from interacting with other proteins. Checkpoint inhibitors (CTLA-4, PD-1, and PD-L1) operate by this mechanism. Briefly, checkpoint inhibitors are proteins that normally help to slow immune responses and prevent the immune system from attacking normal cells. Checkpoint inhibitors bind these proteins and prevent them from functioning normally, which increases the activity of the immune system. Examples include durvalumab, ipilimumab, nivolumab, and pembrolizumab.
Their capacities only allow them to be considered equivalent to what are now known as AI Cores, small (in the literal physical sense) Artificial intelligences used in shuttles, trans-light modules, Drones, and other machines not large enough for a full scale Mind. While still considered sentient, a mind's power at this point is considered greatly inferior to a contemporary Mind. That said, It is possible for Minds to have upgrades, improvements and enhancements given to them since construction, to allow them to remain up to date. Using the sensory equipment available to the Culture, Minds can see inside solid objects; in principle they can also read minds by examining the cellular processes inside a living brain, but Culture Minds regard such mindreading as taboo. The only known Mind to break this Taboo, the GCU Grey Area seen in Excession, is largely ostracised and shunned by other Minds as a result. In Look to Windward an example is cited of an attempt to destroy a Culture Mind by smuggling a minuscule antimatter bomb onto a Culture orbital inside the head of a Chelgrian agent. However the bomb ends up being spotted without the taboo being broken. In Consider Phlebas, a typical Mind is described as a mirror-like ellipsoid of several dozen cubic metres, but weighing many thousands of tons, due to the fact that it is made up of hyper-dense matter. It is noted that most of its 'body' only exists in the real world at the outer shell, the inner workings staying constantly within hyperspace.
==== Medical waste management program ==== California created the Medical Waste Management Program, which regulates the generation, handling, storage, treatment, and disposal of medical waste by providing oversight for the implementation of the Medical Waste Management Act. Precautions have been taken in California which permits and inspects all medical waste offsite treatment facilities and medical waste transfer stations. In order to dispose waste, the department recommends the following process to make controlled substance waste non-retrievable. Pills containing a controlled substance are crushed before placing the residue into a pharmaceutical waste container. Controlled substance that is remaining in a syringe is wasted into a pharmaceutical waste container before disposing of the syringe in a sharps container. Expired medications should be returned through a reverse distributor.
The AToFMS allows for the determination of mixing state, or distribution of chemical species, within individual particles. These mixing states are important in the determination of climate and health impact of aerosols. The schematic of a typical AToFMS is shown to the right. The overall structure of ATOF instruments is; sampling, sizing, and the mass analyzer region. The inlet system is similar to the AMS by using the same aerodynamic focusing lens, but it has smaller orifices because of its analysis of single particles. In the sizing region particle passes through the first continuous solid state laser that generates an initial pulse of scattered light. Then the particle passes through the second laser that is orthogonal to the first and produces a pulse of scattered light. The light is detected by a photomultiplier (PMT) that is matched up to each laser. Using the transit times between the two detected pulses and the fixed distance the velocity and size of each particle is calculated. Next the particles travel through to the mass analyzer region where it is ionized by a pulsed LDI laser, which is timed to hit the particle as it reaches the center of the ion extraction region. Once ionized, the positive ions are accelerated towards the positive ToF section and the negative ions are accelerated towards the negative ToF section where they are detected.
=== Alcoholism === Banana bags are often prescribed for alcoholics. Chronic alcoholism can lead to a lack of thiamine, potentially causing Wernicke–Korsakoff syndrome. Chronic alcoholics can also have magnesium deficiency. A 2016 review found that the amount of thiamine in a conventional banana bag is inadequate for prevention or treatment for ICU patients. The proposed regimen is 200–500 mg IV thiamine every eight hours for the first day of admission. Less evidence exists for the use of magnesium and folic acid, for which a smaller change in dosage is proposed. No evidence for the use of multi-vitamins are found for alcoholics. Vitamin C is proposed to be added based on the prevalence of low blood levels among alcoholics, but its usefulness is undefined. Using a base of dextrose solution instead of saline is proposed in case of alcoholic ketoacidosis. Banana bags (more narrowly, thiamine) are under-used when alcoholics present to the hospital with illnesses other than alcohol withdrawal, especially for critical illnesses such as sepsis, traumatic brain injury, and diabetic ketoacidosis. Using thiamine on septic alcoholics seems to reduce the rate of death.
Sources: en.wikipedia.org
== Medical uses == Suvorexant is used for the treatment of insomnia, characterized by difficulties with sleep onset and/or sleep maintenance, in adults. At a dose of 15 to 20 mg and in terms of treatment–placebo difference, it reduces time to sleep onset by up to 10 minutes, reduces time awake after sleep onset by about 15 to 30 minutes, and increases total sleep time by about 10 to 20 minutes. A 2017 systematic review and meta-analysis of randomized controlled trials of suvorexant for insomnia likewise found that the medication improved subjective sleep onset, subjective total sleep time, and subjective sleep quality when assessed at one to three months of treatment. The effectiveness of approved doses of suvorexant (≤20 mg) in the treatment of insomnia is said to be modest. Network meta-analyses have assessed the sleep-promoting effects of suvorexant and have compared them to those of other orexin receptor antagonists like lemborexant and daridorexant as well as to other sleep aids including benzodiazepines, Z-drugs, antihistamines, sedative antidepressants (e.g., trazodone, doxepin, amitriptyline, mirtazapine), and melatonin receptor agonists. A major systematic review and network meta-analysis of insomnia medications published in 2022 found that suvorexant had an effect size (standardized mean difference (SMD)) against placebo for treatment of insomnia at 4 weeks of 0.31 (95% CITooltip confidence interval 0.01 to 0.62).
== Types of nuclear warfare == Nuclear warfare scenarios are usually divided into two groups, each with different effects and potentially fought with different types of nuclear armaments. The first, a limited nuclear war (sometimes attack or exchange), refers to the controlled use of nuclear weapons, whereby the implicit threat exists that a nation can still escalate their use of nuclear weapons. For example, using a small number of nuclear weapons against strictly military targets could be escalated through increasing the number of weapons used, or escalated through the selection of different targets. Limited attacks are thought to be a more credible response against attacks that do not justify all-out retaliation, such as an enemy's limited use of nuclear weapons. The second, a full-scale nuclear war, could consist of large numbers of nuclear weapons used in an attack aimed at an entire country, including military, economic, and civilian targets. Such an attack would almost certainly destroy the entire economic, social, and military infrastructure of the target nation, and would likely have a devastating effect on Earth's biosphere. Some Cold War strategists such as Henry Kissinger argued that a limited nuclear war could be possible between two heavily armed superpowers (such as the United States and the Soviet Union). Some predict, however, that a limited war could potentially "escalate" into a full-scale nuclear war.
6 May 1986 – USS Ray, USS Archerfish and USS Hawkbill meet and surface together at the Geographic North Pole. First three-submarine surfacing at the Pole. 19 May 1987 – HMS Superb joined USS Billfish and USS Sea Devil at the North Pole. March 2007 – USS Alexandria participated in the Joint US Navy/Royal Navy Ice Exercise 2007 (ICEX-2007) in the Arctic Ocean with the Trafalgar-class submarine HMS Tireless. March 2009 – USS Annapolis took part in Ice Exercise 2009 to test submarine operability and war-fighting capability in Arctic conditions.
At the regulatory site, the binding of a ligand may elicit amplified or inhibited protein function. The binding of a ligand to an allosteric site of a multimeric enzyme often induces positive cooperativity, that is the binding of one substrate induces a favorable conformation change and increases the enzyme's likelihood to bind to a second substrate. Regulatory site ligands can involve homotropic and heterotropic ligands, in which single or multiple types of molecule affects enzyme activity respectively. Enzymes that are highly regulated are often essential in metabolic pathways. For example, phosphofructokinase (PFK), which phosphorylates fructose in glycolysis, is largely regulated by ATP. Its regulation in glycolysis is imperative because it is the committing and rate limiting step of the pathway. PFK also controls the amount of glucose designated to form ATP through the catabolic pathway. Therefore, at sufficient levels of ATP, PFK is allosterically inhibited by ATP. This regulation efficiently conserves glucose reserves, which may be needed for other pathways. Citrate, an intermediate of the citric acid cycle, also works as an allosteric regulator of PFK.
Sources: en.wikipedia.org
It is a four-amino-acid peptide with the sequence alanine-glutamate-aspartate-glycine. The chain is unmodified and contains only standard proteinogenic residues, which makes it straightforward to produce by solid-phase synthesis and to characterise by standard peptide methods.
Epitalon and epithalon both circulate, and the difference reflects transliteration of a name coined in Russian-language publications. Reference to the extract it derives from, epithalamin, explains the shared stem. Databases and suppliers are inconsistent, so a search for one spelling alone may miss relevant entries.
No. Epithalamin is a multi-component preparation obtained from pineal tissue, and its exact composition is not fully characterised. Epitalon is a single defined tetrapeptide described as a short synthetic counterpart of that extract, so the two are related in origin but not interchangeable in identity.
Sealed lyophilised powder is normally kept at minus twenty degrees Celsius or below, away from light and moisture. Vials are allowed to reach room temperature before opening to limit condensation. Repeated warming and cooling of the same vial is discouraged.