If you have been reading about Reversed-phase HPLC and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-04-17. Where a claim depends on a specific study, the study is described rather than over-claimed.
Identity and purity are checked by reversed-phase high-performance liquid chromatography, usually with ultraviolet detection near 214 nanometres, where the peptide bond absorbs. Mass spectrometry confirms the expected mass and reveals whether truncation products or adducts are present. Acid hydrolysis followed by amino acid analysis gives the residue ratio, which should approximate one alanine, one glutamate, one aspartate and one glycine. Counter-ions such as acetate or trifluoroacetate remain in the dried product and lower net peptide content, so a stated purity figure on a label does not by itself describe how much peptide a vial holds.
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.
Laboratory work has examined effects on telomerase activity in cultured cells, on melatonin rhythms in animals, and on markers of oxidative stress. Some experiments report measurable changes while others show none, and the reported findings rest largely on small studies. The absence of large independent trials means the generality of these results is unresolved rather than settled. Review articles occasionally apply the label geroprotector, a term that reflects a research hypothesis about ageing rather than an established clinical finding.
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.
| Property | Value | Notes |
|---|---|---|
| Storage temperature, solid | Approximately -20 C | Sealed, desiccated, protected from light |
| Typical identity method | Electrospray mass spectrometry | Protonated ion expected near 391 |
| Typical purity method | Reversed-phase HPLC | Ultraviolet detection near 214 nm |
| Common synonyms | Epithalon, epithalone, AEDG | Spelling variants appear in supplier catalogues |
| Solution stability | Days at 2-8 C | Hydrolysis and deamidation limit shelf life |
No national medicines regulator has approved epitalon as a therapeutic product. It is generally distributed as a research chemical, and in some jurisdictions selling peptides for human consumption without approval is restricted or prohibited. Certificates of analysis accompanying commercial material vary in which tests are performed, and independent verification of identity and purity is uncommon. Statements about anti-ageing or disease-prevention benefits on vendor pages are marketing claims rather than regulatory findings, a distinction that shapes how the compound is discussed in scientific and popular sources alike.
The most frequently cited laboratory finding is that AEDG increased telomerase activity and extended telomere length in cultured human somatic cells. That work used fetal fibroblast strains and reported changes in enzyme activity alongside altered division counts. Replication by unrelated groups has been limited, and the published record is largely a single-laboratory series rather than a multi-centre programme. The result supports a hypothesis about peptide influence on gene expression in cell culture; it does not by itself establish an effect on telomere length in living animals or in people.
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.
Regulatory status varies by country and is not harmonized. Epitalon is not an approved drug in major Western jurisdictions. In some countries it is sold as a research chemical, and in others it has appeared in products marketed for other categories. This inconsistent status means that purity, labeling accuracy, and documentation differ widely between suppliers, and verification of identity and purity through independent analysis is the usual way buyers assess a given lot.
Epitalon appears in the literature primarily through a small number of research groups, most of them associated with the St. Petersburg Institute of Bioregulation and Gerontology. Publications describe cell culture experiments, animal studies, and a limited number of small human studies. Independent replication outside this network is sparse. As a result, reviews of the topic usually separate descriptive reports of observed effects from the question of whether those effects generalize, and they note the difficulty of comparing studies that use different preparations and endpoints.
Similar provisions apply to the issuance of Facilitated Rail Transit Documents by Schengen Area members for travel between Kaliningrad Oblast and the Russian mainland, enabling Russian citizens to travel to and from the exclave without a passport or visa. Many countries allow individuals to clear border controls with foreign visas. Notably, the Philippines permits nationals of India and China can use any of several foreign visas to clear border controls. To encourage tourism by transit passengers, South Korea permits passengers in transit who would otherwise require a South Korean visa to enter for up to thirty days utilizing an Australian, Canadian, American, or Schengen visa. Uniquely, the British territory of Bermuda has ceased issuing its own visas and now requires travellers to either clear immigration visa-free in one of the three countries (Canada, America, and the United Kingdom) to/from which it has direct flights, or hold a visa for one of them.
paracellular transport The transfer of substances across an epithelium by passing through the extracellular space between cells, in contrast to transcellular transport, where substances travel through cells by crossing the intracellular cytoplasm.
=== Cosmetics === Blotting papers are also commonly used in cosmetics to absorb excess sebum oil from the face. They are popularly marketed and have been sold by numerous cosmetic brands worldwide. The papers are often dyed, for wider market appeal, and dusted with salicylic acid and minerals to actively prevent the formation of comedones and acne. However, there is a popular debate of whether blotting papers can help reduce acne by absorbing excess oil, or cause it. The quality of the blotting papers and the use of other ingredients such as mineral oils may be a determining factor.
=== 24 May === Ukrainian authorities ordered the mandatory evacuation of 123 children from 36 settlements in Kharkiv Oblast due to Russian attacks. The United States sent another military aid package for Ukraine, valued at $275 million. It included HIMARS, munitions, 155 mm and 105 mm high-demand artillery rounds, Javelin and AT4 antitank systems, antitank mines, tactical vehicles, small arms and ammunition. The Ukrainian Air Force announced that it had begun using air dropped Small Diameter Bombs, which had "proved resilient to jamming" and had a "nearly 90 percent" accuracy rate, since November 2023.
=== Biomechanics === Complications in the diabetic foot and foot-ankle complex are wider and more destructive than expected and may compromise the structure and function of several systems: vascular, nervous, somatosensory, and musculoskeletal. Thus, a deeper comprehension of the alteration of gait and foot biomechanics in the diabetic foot is of great interest and may play a role in the design and onset of preventive as well as therapeutic actions. Briefly, the effect of diabetes on the main structures of the foot-ankle complex can be summarised as:
Sources: en.wikipedia.org
=== Treatment process === Preliminary testing, preferably on a like textile, is essential to establish a conservation strategy that effectively stabilizes the object through minimal intervention. Treatment starts with the selection of a compatible adhesive and support substrate. The material options are the same as those used for stitching methods. Silk crepeline is popular because it is more pliable than polyester crepeline (Stabiltex), but paper can also be a suitable support depending on the object. Substrata can be dyed to match the color of the textile being consolidated. Surface preparation involves adhesive application by brush, roller, sponge, or spraying in a fume-extraction booth. The prepared substrate is then placed adhesive side down over the textile and covered with absorbent blotting paper that is pinned or weighted. Methods of affixing the adhesive support to the textile artifact include spatula or flat iron, vacuum hot table, vacuum cold-lining, solvent activation, and direct wet or semi-dry application. For instance, cellulose and starch-coated paper can be activated with steam vapor and applied to the textile through vacuum cold-lining creating a bond with the underlying material.
The UK government says that a report published on the GOV.UK website on 27 December that said housing asylum seekers on the Bibby Stockholm barge was discriminatory on the grounds of age and sex was published by mistake. The report is deleted from the website. 30 December Eurostar services to and from London St Pancras are cancelled because of a flood in a tunnel under the River Thames. British Army officer Preet Chandi becomes the fastest woman to complete a trek to the South Pole on skis. Four police officers are injured and eight people arrested following a demonstration in Camberwell, south London, relating to tensions in the local Eritrean community. 31 December American XL bully dogs are added to the list of banned species under the Dangerous Dogs Act 1991 in England and Wales, requiring them to be on a lead and muzzled in public. It is also illegal to breed, sell or abandon the dogs. Eurostar resumes services to and from London St Pancras following the previous day's disruption. Two people killed in an avalanche at the French ski resort of Saint-Gervais-les-Bains on 28 December are named as British mother and son Kate and Archie Vokes.
=== Computational methods in studying protein biomarkers === One example of the use of bioinformatics and the use of computational methods is the study of protein biomarkers. Computational predictive models have shown that extensive and diverse feto-maternal protein trafficking occurs during pregnancy and can be readily detected non-invasively in maternal whole blood. This computational approach circumvented a major limitation, the abundance of maternal proteins interfering with the detection of fetal proteins, to fetal proteomic analysis of maternal blood. Computational models can use fetal gene transcripts previously identified in maternal whole blood to create a comprehensive proteomic network of the term neonate. Such work shows that the fetal proteins detected in pregnant woman's blood originate from a diverse group of tissues and organs from the developing fetus. The proteomic networks contain many biomarkers that are proxies for development and illustrate the potential clinical application of this technology as a way to monitor normal and abnormal fetal development. An information-theoretic framework has also been introduced for biomarker discovery, integrating biofluid and tissue information. This new approach takes advantage of functional synergy between certain biofluids and tissues with the potential for clinically significant findings not possible if tissues and biofluids were considered individually.
== Ribozymes == At the time of the hypercycle theory formulation, ribozymes were not known. After the breakthrough of discovering RNA's catalytic properties in 1982, it was realized that RNA had the ability to integrate protein and nucleotide-chain properties into one entity. Ribozymes potentially serving as templates and catalysers of replication can be considered components of quasispecies that can self-organize into a hypercycle without the need to invent a translation process. In 2001, a partial RNA polymerase ribozyme was designed via directed evolution. Nevertheless, it was able to catalyse only a polymerization of a chain having the size of about 14 nucleotides, even though it was 200 nucleotides long. The most up-to-date version of this polymerase was shown in 2013. While it has an ability to catalyse polymerization of longer sequences, even of its own length, it cannot replicate itself due to a lack of sequence generality and its inability to transverse secondary structures of long RNA templates. However, it was recently shown that those limitations could in principle be overcome by the assembly of active polymerase ribozymes from several short RNA strands. In 2014, a cross-chiral RNA polymerase ribozyme was demonstrated. It was hypothesized that it offers a new mode of recognition between an enzyme and substrates, which is based on the shape of the substrate, and allows avoiding the Watson-Crick pairing and, therefore, may provide greater sequence generality.
==== Micrococcus lysodeikticus ==== By the measurement of decrease in turbidity of M. lysodeikticus by incubating it with lysozyme, enzymatic activity can be evaluated. 7.5 μL of 0.1 - 1 mg/mL proteins is added to 200 μL of M. lysodeikticus at its optical density (OD) of 1.7 AU, and the mixture is measured at 450 nm periodically for reaction rate calculation. On the contrary to the result from glycol chitosan enzymatic activity, the increasing degree of PEGylation decreased the enzymatic activity. This difference in the trend of the enzymatic activity can be due to PEGylation to free lysine causing steric hindrance and subsequently preventing from forming enzyme-substrate complex in the case of reacting with macromolecule, such as M. lysodeikticus.
Sources: en.wikipedia.org
is the difference in the lower energy levels involved in the transitions for the lines being probed. Another way to measure the temperature is by relating the FWHM of the probed absorption line to the Doppler line width of the species at that temperature. This is given by,
=== Regulation === In some jurisdictions, the sale or possession of hypodermic syringes may be controlled or prohibited without a prescription, due to its potential use with illegal intravenous drugs.
In addition the vaccine virus Vaccinia also uses elements of the actin cytoskeleton for its dissemination. Pseudomonas aeruginosa is able to form a protective biofilm in order to escape a host organism's defences, especially white blood cells and antibiotics. The biofilm is constructed using DNA and actin filaments from the host organism. In addition to the previously cited example, actin polymerization is stimulated in the initial steps of the internalization of some viruses, notably HIV, by, for example, inactivating the cofilin complex. The role that actin plays in the invasion process of cancer cells has still not been determined. In conditions of high lipoperoxidation, actin has been shown to be post-translationally modified by the lipoperoxidation product 4-hydroxynonenal (4-HNE). This modification prevents the remodelling of the actin cytoskeleton, which is essential for cell motility. Additionally, another functional protein, coronin-1A, which stabilizes F-actin filaments, is also covalently modified by 4-HNE. These modifications may impair immune cell trans-endothelial migration or their phagocytic ability, potentially leading to a decreased immune response in diseases characterized by high oxidative stress, such as malaria, cancer, metabolic syndrome, atherosclerosis, Alzheimer's disease, rheumatoid arthritis, neurodegenerative diseases, and preeclampsia.
Although most MALS-based measurements are performed in a plane containing a set of detectors usually equidistantly placed from a centrally located sample through which the illuminating beam passes, three-dimensional versions also have been developed wherein the detectors lie on the surface of a sphere with the sample controlled to pass through its center where it intersects the path of the incident light beam passing along a diameter of the sphere. The former framework is used for measuring aerosol particles while the latter was used to examine marine organisms such as phytoplankton. The traditional differential light scattering measurement was virtually identical to the currently used MALS technique. Although the MALS technique generally collects multiplexed data sequentially from the outputs of a set of discrete detectors, the earlier differential light scattering measurement also collected data sequentially as a single detector was moved from one collection angle to the next. The MALS implementation is of course much faster, but the same types of data are collected and are interpreted in the same manner. The two terms thus refer to the same concept. For differential light scattering measurements, the light scattering photometer has a single detector whereas the MALS light scattering photometer generally has a plurality of detectors. Another type of MALS device was developed in 1974 by Salzmann et al. based on a light pattern detector invented by George et al. for Litton Systems Inc. in 1971.
Sources: en.wikipedia.org
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.
Reversed-phase chromatography with ultraviolet detection gives a purity percentage, while mass spectrometry confirms identity. Amino acid analysis checks the residue composition. Buyers typically request a certificate of analysis showing these measurements for the specific lot.
It is not authorised as a medicine in the United States or the European Union. Material is sold there as a research chemical or cosmetic ingredient. Some related short peptides are registered drugs in Russia, which is a distinct national situation rather than a general approval.
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.