This is a working overview of Deamidation, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-05-24. Anything still debated is marked as such rather than presented as settled.
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.
Published evidence comes mainly from Russian-language journals and from a single research group, with small sample sizes and limited independent replication. A few laboratories outside that group have examined related peptides and reported weaker or absent telomerase effects, so the central claim is best described as contested rather than settled. Rodent studies report modest changes in some ageing markers and in survival, but designs vary and control conditions are often sparse. No large randomised trial in humans has been published, and long-term safety data in healthy populations are correspondingly thin.
Epitalon is a synthetic tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, commonly abbreviated AEDG. It was designed at the St. Petersburg Institute of Bioregulation and Gerontology as a short, chemically defined analogue of epithalamin, a fraction obtained from bovine pineal tissue. Small peptide bioregulators of this type formed a long-running line of work there from the 1980s onward. Because the molecule is produced by solid-phase synthesis rather than extraction, its composition is exact and its purity can be measured directly.
The most frequently cited proposed action is induction of telomerase, the enzyme that adds repeat sequences to chromosome ends. Cell-culture work from the originating group reported higher telomerase reverse transcriptase expression and measurable telomere elongation in human somatic cells after exposure. How a four-residue peptide would reach nuclear gene regulation is not established, and no cell-surface receptor or uptake route has been identified. Additional reports describe changes in melatonin secretion, antioxidant enzyme activity and lipid peroxidation in aged animals, but these findings remain mechanistically unconnected to the telomerase observation.
| Property | Value | Notes |
|---|---|---|
| Analytical method | Reversed-phase HPLC | Purity determination, typically 214 nm |
| Mass confirmation | ESI or MALDI mass spectrometry | Compared with mass near 390 Da |
| Common synonyms | Epitalon, epithalon, AEDG | Naming differs between suppliers |
| Storage temperature | −20 °C or lower | Lyophilised powder, kept desiccated |
| Solution stability | Limited in neutral aqueous buffer | Aspartimide and hydrolysis pathways |
No pharmacopoeial monograph exists for this peptide, so quality rests on the supplier's internal specifications and on whatever independent testing a purchaser arranges. Certificates of analysis differ widely in which tests they report and in the limits applied. The counter-ion introduced during purification, commonly acetate or trifluoroacetate, changes the net peptide content of a given mass of powder, so two samples of equal weight may not contain equal amounts of the active sequence. Third-party laboratories can verify purity, identity, residual solvents, and counter-ion content for a fee, which makes documentation more informative than labelling.
Verification of a sample usually begins with reversed-phase high-performance liquid chromatography, which resolves the peptide from truncated sequences and other impurities and expresses purity as a percentage of total peak area. Mass spectrometry by electrospray ionisation or matrix-assisted laser desorption supplies an independent check, because the measured mass can be compared against the theoretical value for AEDG. Amino acid analysis or tandem mass spectrometry sequencing can confirm residue order. Each of these methods answers a different question: a purity figure does not establish identity, and an identity match does not establish how much of the material is intact peptide.
The molecule is a short, linear, hydrophilic peptide that dissolves readily in water or aqueous buffer. Its principal chemical liabilities are hydrolytic rather than oxidative, since it contains no cysteine, methionine, or tryptophan residues. The aspartate–glycine step is a recognised site for aspartimide formation under mildly acidic or basic conditions, generating isoaspartate and succinimide-related products over time. Desiccated lyophilised powder held at −20 °C is comparatively stable, whereas dilute solutions degrade faster and are best frozen as single-use aliquots rather than thawed repeatedly.
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.
Lyophilised epitalon is generally held at minus twenty degrees Celsius in a sealed container kept dry and dark. Cooler conditions are sometimes recommended for long-term archives. The solid takes up moisture readily enough that repeated opening of a vial introduces water, so dividing a batch into smaller portions before storage lowers degradation risk. Aqueous solutions are less durable than the dry powder and are usually prepared shortly before use, then kept cold and shielded from light to slow hydrolysis and oxidation.
Verification of research-grade material involves comparing a supplier chromatogram against an in-house reference, checking the observed mass against the calculated value, and where possible confirming residue order by tandem mass spectrometry or enzymatic peptide mapping. Purity claims should be read alongside the method used to obtain them, because detection wavelength and integration settings alter the result. Batch-specific data, rather than a generic grade statement, is the informative part of a certificate.
Identity and purity of epitalon samples are normally established by reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres, combined with mass spectrometry. The mass spectrum confirms the expected molecular ion and can reveal truncated or oxidised by-products. Amino acid analysis after acid hydrolysis verifies that the four residues are present in the expected ratio. Certificates typically report a purity figure taken from chromatographic peak area, expressed as a percentage of total integrated signal.
=== Mechanical engineer === In 1912, Jones moved to Hallock, Minnesota, where he worked as a mechanic on a 50,000-acre (200 km2) farm. The farm was owned by James J. Hill, who was also owner of the Great Northern Railroad. Jones' proximity to Hill and the railroad facilitated his education in electricity and steam locomotive engines. Jones lived there for more than 20 years and would later say in a newspaper article that Hallock was a place "where a man … [was] judged more on his character and ability than on the color of his skin." He was locally known as "Casey" due to a remark by a railroad engineer he met while working at Hill Farm (see also Casey Jones). Jones received his engineering license at age 20. He later upgraded his license to the highest grade.
=== 2011 recalls of Simvastatin and Toprol products === In June 2011, certain lots of Dr. Reddy's generic Simvastatin tablets were recalled due to tablets having a "musty" or "moldy" smell. On 24 June 2014, The New York Times published an article "Warning Unheeded, Heart Drugs Are Recalled" in which it said another large Indian manufacturer and "Dr. Reddy's Laboratories, have announced recalls over the past two months totalling more than 100,000 bottles" of "a widely used heart drug, Toprol XL" "because their products were not dissolving properly".
Hatching is an exhausting effort for the neonates, which break out of their eggshells with an egg tooth that falls off before long. After cutting themselves out, the hatchlings may lie in their eggshells for hours before starting to dig out of the nest. They are born quite defenseless and are vulnerable to predation. Sixteen youngsters from a single nest were on average 46.5 cm long and weighed 105.1 grams.
== External links == visfatin,+human at the U.S. National Library of Medicine Medical Subject Headings (MeSH) NAMPT human gene location in the UCSC Genome Browser. NAMPT human gene details in the UCSC Genome Browser. Overview of all the structural information available in the PDB for UniProt: P43490 (Human Nicotinamide phosphoribosyltransferase) at the PDBe-KB. Overview of all the structural information available in the PDB for UniProt: Q99KQ4 (Mouse Nicotinamide phosphoribosyltransferase) at the PDBe-KB.
=== Motility assays === Agarose is sometimes used instead of agar to measure microorganism motility and mobility. Motile species will be able to migrate, albeit slowly, throughout the porous gel and infiltration rates can then be visualized. The gel's porosity is directly related to the concentration of agar or agarose in the medium, so different concentration gels may be used to assess a cell's swimming, swarming, gliding and twitching motility. Under-agarose cell migration assay may be used to measure chemotaxis and chemokinesis. A layer of agarose gel is placed between a cell population and a chemoattractant. As a concentration gradient develops from the diffusion of the chemoattractant into the gel, various cell populations requiring different stimulation levels to migrate can then be visualized over time using microphotography as they tunnel upward through the gel against gravity along the gradient.
Sources: en.wikipedia.org
=== Thermal modulation === Thermal modulators use broad temperature differentials (by way of hot and cold jets) to trap and release analytes eluting out of the primary column. Commercial devices typically use two-stage modulation either via a quad jet approach (where there are two pairs of jets to trap and release the analytes on two different sections of the column) or a delay loop (where the column loops back between a single pair of jets). Both approaches ensure there are two opportunities to focus the analytes. There are also different versions of thermal modulators based on what is used to cool the cold jet (a stream of dry gas, usually air or nitrogen). Liquid nitrogen cooled loop system provide the lowest temperature for thermal modulation, meaning it is capable of modulating volatiles from C2. However, there is the compromise that liquid nitrogen is expensive and causes additional health and safety concerns. Alternatively, consumable-free thermal modulators are available that use a closed cycle refrigeration unit to cool the cold jet.
As part of a comprehensive modernization of German radiation protection law, which is largely based on Directive 2013/59/Euratom, the provisions of the X-Ray Ordinance have been incorporated into the revised Radiation Protection Ordinance. Among many other measures, contaminated food was withdrawn from the market on a large scale. Parents were strongly advised not to let their children play in sandboxes. Some of the contaminated sand was replaced. In 1989, the Federal Office for Radiation Protection was incorporated into the Ministry of the Environment. On April 30, 2003, a new precautionary radiation protection law was promulgated to implement two EU directives on the health protection of persons against the dangers of ionizing radiation during medical exposure. The protection of workers from optical radiation (infrared radiation (IR), visible light (VIS) and ultraviolet radiation (UV)), which falls under the category of non-ionizing radiation, is regulated by the Ordinance on the Protection of Workers from Artificial Optical Radiation of 19 July 2010. It is based on the EU Directive 2006/25/EC of April 27, 2006. On March 1, 2010, the "Act on the Protection of Humans from Non-Ionizing Radiation" (NiSG), BGBl. I p. 2433, came into force, according to which the use of sunbeds by minors has been prohibited since August 4, 2009, in accordance with § 4 NiSG [Network and Information Systems Security Ordinance – NIS Ordinance] (in German) A new Radiation Protection Act came into force in Germany on October 1, 2017.
=== Magnetotaxis === The movement and orientation of "Ca. M. multicellularis" appears to be altered by many external stimuli as it undergoes magnetotaxis, photokinesis, negative phototaxis and potentially helical klinotaxis. The organism contains multiple internal magnetosomes, membrane-bound structures containing magnetic nanocrystals. In "Ca. M. multicellularis" these crystals are greigite (Fe3S4) but in most other species of multicellular magnetotactic bacteria (MMB) the crystals are magnetite (Fe3O4). These magnetosomes are organised in linear chains that allow the consortium to orient itself along the Earth's geomagnetic field. In samples from the Southern Hemisphere, "Ca. M. multicellularis" exhibits a preference for south-facing orientation while swimming. In weak magnetic fields, under 80 μT, "Ca. M. multicellularis" behaves differently to other magnetotactic bacteria. Under fields close to or weaker than Earth's geomagnetic field, its trajectories appear significantly scattered away from the exact magnetic field line. In these situations, movement relies mostly on a combination of other environmental factors and the direction of the magnetic field line does not fully control the final swimming direction.
O.R. Tambo is focused on most of SA's manufactured exports and imports Cape Town International deals primarily with agricultural exports, such as fruit, flowers, and seafood King Shaka International supports manufacturing and automotive exports Out of all air freight flowing through South Africa's airports, O.R. Tambo handles Major players in the South African air freight sector include South African Airways Cargo, Ethiopian Cargo, Qatar Airways Cargo, Emirates SkyCargo, Lufthansa Cargo, Turkish Cargo, and Cargolux. Freight forwarders such as DHL, FedEx, UPS, and DSV also play a large role in the sector.
=== Seth Holt === Seth Holt (John Corbett) is Sarah's rocker ex-husband and Amber and Drew's absent father. Seth is a traveling musician and has never made much time for either of his children. Sarah left Seth due to his chronic problems with drugs and alcohol, and she constantly had to lie to her children regarding his long absences, saying he was away on tour. He shares a bond with his son Drew, who visits him during the "Pilot." Seth calls Drew on Thanksgiving after Zeek leaves him a voicemail. Seth comes back to town and bonds with Drew again. After Drew tells Sarah that Seth is back in town, she visits him and the two talk. Seth reveals that he has been sober for the last nine months, and Sarah finally lets Drew and Amber see him. While Drew has a good relationship with Seth, Amber is less forgiving and resents her father for never being there. Eventually, Seth leaves to go back on tour. Seth visits Sarah while he is drunk, and she attempts to help him get sober. Seth finally agrees to admit himself to rehab, and he and Sarah get closer again even though she is in a committed relationship with Mark Cryr. After Seth gets clean, he kisses Sarah, but she breaks it off. Amber asks Seth to leave after overhearing Sarah talk about the kiss. Seth leaves to stay with his cousin Eric in Tahoe, leaving packages of birthday cards for both Amber and Drew to make up for all the birthdays he missed through the years. Later in the season, Sarah calls to tell Seth that she and Mark are trying to have a baby, which upsets him.
Sources: en.wikipedia.org
=== Switch to IFCC units === The American Diabetes Association, European Association for the Study of Diabetes, and International Diabetes Federation have agreed that, in the future, HbA1c is to be reported in the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) units. IFCC reporting was introduced in Europe except for the UK in 2003; the UK carried out dual reporting from 1 June 2009 until 1 October 2011. Conversion between DCCT and IFCC is by the following equation:
==== Radical site-initiated fragmentation ==== Sigma bond cleavage also occurs on radical cations remote from the site of ionization. This is commonly observed in alcohols, ethers, ketones, esters, amines, alkenes, and aromatic compounds with a carbon attached to ring. The cation has a radical on a heteroatom or an unsaturated functional group. The driving force of fragmentation is the strong tendency of the radical ion for electron pairing. Cleavage occurs when the radical and an odd electron from the bonds adjacent to the radical migrate to form a bond between the alpha carbon and either the heteroatom or the unsaturated functional group. The sigma bond breaks; hence this cleavage is also known as homolytic bond cleavage or α-cleavage.
=== Pharmacodynamics === Metribolone is an AAS, or an agonist of the AR, with both anabolic and androgenic activity. It is one of the most potent AAS to have ever been synthesized, with 120 to 300 times the oral anabolic potency and 60 to 70 times the androgenic potency of the reference AAS methyltestosterone in castrated male rats, although the same level of potency has not been observed in studies in humans. In addition to the AR, metribolone has high affinity for the progesterone receptor (PR), and binds to the glucocorticoid receptor (GR) as well. The drug was also identified in 2007 as a potent antimineralocorticoid, with similar affinity for the mineralocorticoid receptor as aldosterone and spironolactone. In addition, metribolone was identified in 2010 as a potent inhibitor of 3β-hydroxysteroid dehydrogenase (3β-HSD) 1 and 2 (IC50 = 0.02 and 0.16 μM, respectively). On the basis of this finding, it has been said that metribolone should be used very cautiously in scientific research, taking into account 3β-HSD inhibition to avoid erroneous interpretation. Metribolone has a high potential for hepatotoxicity, similarly to other 17α-alkylated AAS. However, the hepatotoxic potential of metribolone appears to be exceptionally high, likely in relation to its very high potency and metabolic stability; in a study of treatment with the drug for advanced breast cancer, severe hepatic dysfunction was observed at very low dosages.
== Since November 2022 == On April 20, 2023, Twitter (known as X since July 2023) began removing verification status for users of public interest, causing a controversy among Twitter users. The website's system was altered, allowing any individual to receive verification for a monthly fee, an act which saw significant criticism. Following the acquisition of Twitter by Elon Musk on October 28, 2022, Musk told Twitter employees to introduce paid verification by November 7 through Twitter Blue. The Verge reported that the updated Blue subscription would cost $19.99 per month, and users would lose their verification status if they did not join within 90 days. Following backlash, Musk tweeted, in response to author Stephen King, a lowered $8 price on November 1, 2022. Twitter confirmed the new price of $7.99 per month on November 5, 2022. The new verification system began rollout on November 9, 2022, a day after the 2022 United States elections. The decision to delay its rollout was to address concerns about users potentially spreading misinformation about voting results by posing as news outlets and lawmakers. At the same time, Twitter introduced a secondary gray "Official" label on some high-profile accounts, but removed them hours after launch. Less than 48 hours later, Twitter reinstated the gray "Official" label, after multiple users were suspended for deliberately impersonating reporters and high-profile athletes like LeBron James.
=== Tetrapods === The myomeres of tetrapods run vertically and do not undergo folding like in bony fishes. Further, in higher order vertebrates, myomeres are fused and run longitudinally. Myosepta are not present in amniotes as amniote muscles are arranged differently. In salamanders, hypaxial muscles, myomeres, and myosepta run in a straight line mid-laterally to mid-ventrally. Specifically, the orientation of collagen fibers within these myomeres runs mediolateral. It is also theorized that, in salamanders, myosepta increase the amplification of strain of angled muscle fibers. This controls how myomeres bulge during contraction in what is called the 'bulge control hypothesis'. Salamanders in the genus Necturus (mudpuppies) are a salamander species with simply-lain myomeres, unlike the complex nature of bony fishes. Myomeres also play a role in swimming in adult newts. Specifically, epaxial myomeres located opposite to each other at the same longitudinal site alternate rhythmic contraction. During stepping on the ground, the myomeres of the mid-trunk undergo bursts of contraction that are synchronized in contrast to double bursting patterns (in opposite directions) expressed in the anterior and posterior trunks.
Sources: en.wikipedia.org
The molecule lacks aromatic residues, so it absorbs weakly near 280 nanometres, the wavelength applied to many other peptides. The peptide bond absorbs strongly below 220 nanometres, making 214 nanometres a practical compromise. Gradient methods must therefore use mobile phases with low ultraviolet absorbance to keep the baseline clean.
Neutral and slightly basic aqueous conditions promote aspartimide formation at the aspartate-glycine step, often followed by deamidation. Elevated temperature and repeated freeze-thaw cycles accelerate the loss. Acidic solutions and dry lyophilised powder are comparatively stable over short periods.
No monograph exists in the United States Pharmacopeia or the European Pharmacopoeia, and no widely distributed certified reference standard is available. Purity and identity therefore rest on supplier methods that are not harmonised. This absence is the main reason reported purities are difficult to compare between sources.
No. Epithalamin is a peptide-containing extract of bovine pineal glands, while epitalon is a single synthetic tetrapeptide. The extract contains many peptides and other tissue components, so its composition varies between batches in ways that a synthesised sequence does not.