Everything below concerns RP-HPLC. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-04-24. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Epitalon is a synthetic tetrapeptide whose sequence is alanine-glutamate-aspartate-glycine, written in single-letter code as AEDG. The four residues are joined by three peptide bonds, giving a linear backbone with no branching and no disulfide bridges. Its calculated molecular mass for the free form is approximately 390.3 daltons, a figure that rises when the compound is supplied as an acetate or trifluoroacetate salt. Because the chain is short, the molecule is defined entirely by its residue order rather than by any folded three-dimensional structure.
Regulatory treatment differs by country. No formulation of epitalon holds a marketing authorisation as a medicine in the United States or the European Union, where material sold for laboratory use is handled as a research chemical and is not intended for human consumption. In Russia, several short peptide preparations from the same institute's peptide series are registered medicinal products, and epitalon appears in that national context. Elsewhere it is frequently offered as a cosmetic ingredient, a category with lighter requirements. Advertising claims about longevity or disease prevention are restricted in most jurisdictions, which limits how sellers describe the compound.
Freeze-dried epitalon is normally kept at minus twenty degrees Celsius in a sealed, desiccated container, protected from light. Short excursions at ambient temperature during shipping are generally tolerated, but repeated warming and cooling cycles encourage moisture uptake, which shortens shelf life. Once dissolved, the peptide is far less stable than the solid: aqueous solutions are subject to hydrolysis and to deamidation at the aspartate and glutamate residues. Working solutions are therefore held refrigerated and used within days, and repeated freezing and thawing of the same vial is best avoided.
| 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 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.
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.
Because epitalon has no pharmacopoeial monograph, quality assessment depends on supplier documentation and independent testing. Certificates of analysis typically report a purity figure from a single chromatographic run, a measured mass and sometimes an appearance description, but methods and acceptance criteria are not harmonised across vendors. Third-party laboratories can repeat identity and purity measurements, and mismatches between labelled and measured peptide content have been described for research peptides generally. What constitutes adequate identity confirmation for a molecule of this size stays an open question, since mass agreement alone does not separate closely related sequences.
Identity testing for epitalon relies on reversed-phase high-performance liquid chromatography for purity and mass spectrometry for mass confirmation. Because the sequence contains no tryptophan or tyrosine, ultraviolet detection at 280 nanometres is insensitive, so chromatographic methods usually monitor absorbance near 214 nanometres, where the peptide backbone absorbs. Electrospray ionisation or matrix-assisted laser desorption/ionisation then checks the intact mass against the expected value near 390 daltons. Peptide mapping or amino acid analysis after acid hydrolysis can supplement these measurements, although such confirmatory work is seldom reported on commercial certificates of analysis.
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.
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.
Factor VIII is bound to VWF while inactive in circulation; factor VIII degrades rapidly when not bound to VWF. Factor VIII is released from VWF by the action of thrombin. In the absence of VWF, factor VIII has a half-life of 1–2 hours; when carried by intact VWF, factor VIII has a half-life of 8–12 hours. VWF binds to collagen, e.g., when collagen is exposed beneath endothelial cells due to damage occurring to the blood vessel. Endothelium also releases VWF which forms additional links between the platelets' glycoprotein Ib/IX/V and the collagen fibrils VWF binds to platelet GpIb when it forms a complex with gpIX and gpV; this binding occurs under all circumstances, but is most efficient under high shear stress (i.e., rapid blood flow in narrow blood vessels, see below). VWF binds to other platelet receptors when they are activated, e.g., by thrombin (i.e., when coagulation has been stimulated). VWF plays a major role in blood coagulation. Therefore, VWF deficiency or dysfunction (von Willebrand disease) leads to a bleeding tendency, which is most apparent in tissues having high blood flow shear in narrow vessels. From studies it appears that VWF uncoils under these circumstances, decelerating passing platelets. Recent research also suggests that von Willebrand Factor is involved in the formation of blood vessels themselves, which would explain why some people with von Willebrand disease develop vascular malformations (predominantly in the digestive tract) that can bleed excessively.
== Common biopolymers == Collagen: Collagen is the primary structure of vertebrates and is the most abundant protein in mammals. Because of this, collagen is one of the most easily attainable biopolymers, and used for many research purposes. Because of its mechanical structure, collagen has high tensile strength and is a non-toxic, easily absorbable, biodegradable, and biocompatible material. Therefore, it has been used for many medical applications such as in treatment for tissue infection, drug delivery systems, and gene therapy. Silk fibroin: Silk Fibroin (SF) is another protein rich biopolymer that can be obtained from different silkworm species, such as the mulberry worm Bombyx mori. In contrast to collagen, SF has a lower tensile strength but has strong adhesive properties due to its insoluble and fibrous protein composition. In recent studies, silk fibroin has been found to possess anticoagulation properties and platelet adhesion. Silk fibroin has been additionally found to support stem cell proliferation in vitro. Gelatin: Gelatin is obtained from type I collagen consisting of cysteine, and produced by the partial hydrolysis of collagen from bones, tissues and skin of animals. There are two types of gelatin, Type A and Type B. Type A collagen is derived by acid hydrolysis of collagen and has 18.5% nitrogen. Type B is derived by alkaline hydrolysis containing 18% nitrogen and no amide groups. Elevated temperatures cause the gelatin to melts and exists as coils, whereas lower temperatures result in coil to helix transformation.
Thirdly and most importantly, IUPAC rejected the name seaborgium for element 106, having just approved a rule that an element could not be named after a living person, even though the IUPAC had given the LBNL team the sole credit for its discovery. In 1997, IUPAC renamed elements 104 to 109, and gave elements 104 and 106 the Berkeley proposals rutherfordium and seaborgium. The name dubnium was given to element 105 at the same time. The 1997 names were accepted by researchers and became the standard.
Coffee contains flavor and aroma qualities that are created due to the Maillard reaction during roasting. An instant coffee can be produced by freeze-drying a water extract of roasted beans. Compared to other drying methods like room temperature drying, hot-air drying, and solar drying, Robusta coffee beans that were freeze-dried contained higher amounts of essential amino acids like leucine, lysine, and phenylalanine. Also, a few non-essential amino acids that significantly contributed to taste were preserved.
In organic chemistry, secondary amino acids are amino acids which do not contain the amino group −NH2 but are rather a secondary amine (>NH). Secondary amino acids can be classified to cyclic acids, such as proline, and acyclic N-substituted amino acids. In nature, proline, hydroxyproline, pipecolic acid and sarcosine are well-known secondary amino acids. Proline is the only proteinogenic secondary amino acid; all other secondary amino acids are non-proteinogenic. Hydroxyproline is incorporated into proteins by hydroxylation of proline. Pipecolic acid, a heavier analog of proline, is found in efrapeptin. Sarcosine is a N-methylated glycine in which the methyl group is used in many biochemical reactions. Azetidine-2-carboxylic acid is a smaller homolog of proline that is found in plants.
Sources: en.wikipedia.org
In 1945, the Vietnamese were locked in a struggle over the destiny of their post-colonial state after the ousting of the French and the surrender of Japan. Viet Minh forces seized control from the collapsing Empire of Vietnam, while the Vietnam Nationalist Party and Việt Cách advanced in Tonkin with the support of the Chinese Allied mission, and the Đại Việt Nationalist Party already posed serious competition to the Viet Minh. The South fractured between the Stalinist front Viet Minh and rival groups including the Trotskyists, Hòa Hảo, Cao Đài, and Bình Xuyên. The Indochinese Communist Party was primarily responsible for starting widespread Vietnamese-on-Vietnamese violence. Its Viet Minh front aimed to consolidate power through the terrorization and purging of the rival Vietnamese groups. In 1946, the Franco-Chinese and Ho–Sainteny Agreements enabled French forces to replace the Chinese north of the 16th parallel and facilitated a coexistence between the DRV and the French that strengthened the Viet Minh while undermining the nationalists. That summer, the Viet Minh colluded with French forces to eliminate nationalists, targeted for their ardent anti-colonialism. By eliminating the nationalist parties, the Viet Minh had undermined Vietnam's broader ability to resist French reconquest. The Bình Xuyên organized crime group also sought power in the country and although they initially fought alongside the Việt Minh, they would later support Bảo Đại.
== Ligation reaction == The mechanism of the ligation reaction was first elucidated in the laboratory of I. Robert Lehman. Two fragments of DNA may be joined by DNA ligase which catalyzes the formation of a phosphodiester bond between the 3'-hydroxyl group (-OH) at one end of a strand of DNA and the 5'-phosphate group (-PO4) of another. In animals and bacteriophages, ATP is used as the energy source for the ligation, while in bacteria, NAD+ is used. The DNA ligase first reacts with ATP or NAD+, forming a ligase-AMP intermediate with the AMP linked to the ε-amino group of lysine in the active site of the ligase via a phosphoramide bond. This adenylyl group is then transferred to the phosphate group at the 5' end of a DNA chain, forming a DNA-adenylate complex. Finally, a phosphodiester bond between the two DNA ends is formed via the nucleophilic attack of the 3'-hydroxyl at the end of a DNA strand on the activated 5′-phosphoryl group of another. A nick in the DNA (i.e. a break in one strand of a double-stranded DNA) can be repaired very efficiently by the ligase. However, a complicating feature of ligation conducted presents itself when ligating two separate DNA ends as the two ends need to come together before the ligation reaction can proceed. In the ligation reactions conducted in a laboratory, the ligation of DNA with sticky or cohesive ends, the protruding strands of DNA may be annealed together already, therefore it is a relatively efficient process as it is equivalent to repairing two nicks in the DNA.
==== Extracellular proteases ==== The green microalgae Chlamydomonas coccoides and Dunaliella sp. and chlorella sphaerkii (a unicellular marine chlorophyte) were found to produce extracellular proteases. The diatom Chaetoceros didymus releases substantial amounts of proteases into the medium, this production is induced by the presence of the lytic bacterium Kordia algicida and is connected to the resistance of this alga against the effects of this bacterium. Some proteases are of functional importance in viral life cycles, thus being attractive targets for drug development.
In 2007, IGN described Half-Life as one of the most influential video games, and in 2013 wrote that the history of the FPS genre "breaks down pretty cleanly into pre-Half-Life and post-Half-Life eras". In 2021, the Guardian ranked Half-Life the third-greatest game of the 1990s, writing that it "helped write the rulebook for how games tell their stories without resorting to aping the conventions of film".
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.
The solid is kept cold, dry and dark, typically at minus twenty degrees Celsius, in a sealed container with desiccant. Dissolved material is kept refrigerated and used promptly. Freezing and thawing a solution repeatedly is avoided because it accelerates degradation.