A practical reference on RP-HPLC: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-04-26. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| 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 |
Storage recommendations center on limiting moisture, heat, and light. The dry powder is generally kept at minus 20 degrees Celsius, and some suppliers recommend minus 80 degrees for long-term archival. Once dissolved, solutions are usually aliquoted and frozen to avoid repeated freeze-thaw cycles, which can promote aggregation or degradation. Aqueous stability depends on pH and concentration, and buffered saline is often preferred over plain water for biological work. Stability data specific to epitalon remain limited, so general peptide-handling practices are applied by analogy rather than from product-specific validation.
Epitalon is a synthetic tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, abbreviated AEDG. Its molecular formula is C14H22N4O9 and its calculated monoisotopic mass is approximately 390.35 daltons. The compound does not occur naturally as a free peptide; it is produced by solid-phase peptide synthesis. Because it contains two acidic residues and no basic residues, the neutral form carries a net negative charge at physiological pH. This charge profile influences how the peptide behaves in solution and during chromatographic analysis.
Laboratory-grade epitalon is typically supplied as a lyophilized powder. Purity is commonly assessed with reverse-phase high-performance liquid chromatography, often paired with mass spectrometry to confirm molecular identity. Amino acid analysis and peptide mapping can provide additional confirmation of sequence. Certificates of analysis for research materials frequently report purity above 95 percent, although the methods behind such figures vary between suppliers. The absence of a pharmacopeial monograph means that no single standardized assay defines the compound, so reported results depend on the analytical protocol chosen.
Analytical characterization of epitalon relies on standard peptide methods. Reverse-phase high-performance liquid chromatography is used to assess purity, and mass spectrometry confirms identity by checking the observed mass against the expected value near 390 daltons. Amino acid analysis can verify composition. Because the peptide is short and hydrophilic, it elutes early on many reverse-phase columns, so method development often requires ion-pairing reagents to achieve adequate retention and resolution from related impurities.
Storage and handling follow conventional peptide practice. Lyophilized epitalon is typically kept refrigerated or frozen, protected from moisture and light, and allowed to equilibrate to room temperature before opening to avoid condensation. Once dissolved, aqueous solutions are usually stored cold and used within a short period, since dilute peptide solutions can support microbial growth and may slowly degrade. The absence of cysteine and methionine reduces, but does not eliminate, oxidation concerns during long-term storage.
Chin J. B., ed. Control of Communicable Diseases Manual. 17th ed. APHA [American Public Health Association] Press; 2000. ISBN 978-0-87553-189-2 Red Book: 2009 Report of the Committee on Infectious Diseases. 2009. American Academy of Pediatrics. 28th ed. ISBN 978-1-58110-306-9 Centers for Disease Control and Prevention. CDC Works 24/7. Retrieved on August 4, 2009.
According to the February 1921 census, 3,123,000 native German speakers lived in Czechoslovakia, 23.4% of the total population. The controversies between the Czechs and the German-speaking minority lingered on throughout the 1920s and intensified in the 1930s. During the Great Depression, the mostly-mountainous regions populated by the German minority, together with other peripheral regions of Czechoslovakia, were hurt by the economic depression more than the interior of the country was. Unlike the less developed regions (Carpathian Ruthenia, Moravian Wallachia), the Sudetenland had a high concentration of vulnerable export-dependent industries (such as glass works, textile industry, paper-making and toy-making industry). Sixty percent of the bijouterie and glassmaking industry were located in the Sudetenland, and 69% of employees in the sector were German-speaking according to mother tongue, and 95% of bijouterie and 78% of other glassware was produced for export. The glass-making sector was affected by decreased spending power and by protective measures in other countries, and many German workers lost their work. The high unemployment, as well as the imposition of Czech in schools and all public spaces, made people more open to populist and extremist movements such as fascism, communism and German irredentism. In those years, parties of German nationalists and later the Sudeten German Party (SdP), with its radical demands gained immense popularity, among Germans in Czechoslovakia.
== Suicide == Since 2013, the National Suicide Observatory has published data on suicide trends in France. Sociological and demographic factors influence the incidence and outcome of suicide across genders.
Gottron's papules are violaceous erythematous papules that commonly occur overlying the dorsal interphalangeal (DIP) or metacarpophalangeal joints (MCP), as well as the elbows or knee joints. They are found in approximately 70 percent of patients diagnosed with dermatomyositis.
Sources: en.wikipedia.org
==== September ==== The Syrian Observatory for Human Rights reported that Firas Hamayel, a commander in the National Guard, was killed in an ambush in Suwayda. On 21 September, Ayoob Kara, former member of the Israeli Knesset, announced the independence of Suwayda, declaring "We proclaim September 21, 2025, as the historic day of Suwayda’s separation from Syria and from the terrorist government of Ahmed Al-Sharaa". On 26 September, the Syrian Druze militias established a local women's self-defense army as a response to the precarious security situation. More than 500 women are involved. Minors have been forcibly trained to use weapons. On 27 September, the Syrian transitional government bombed the city of Mecdel with a drone and also bombed the city of Kanaker.
Holders of more than 99% of the shares elected to participate. Holmes contributed shares to the company and gave up equity to offset potential dilution to non-participating shareholders. In May 2018, John Carreyrou reported that American business and government leaders lost more than $600 million by privately investing in Theranos. Major investments had been made by the Walton family ($150 million), Rupert Murdoch ($121 million), Betsy DeVos ($100 million), the Cox family (of Cox Media Group) ($100 million) and Larry Ellison. The final liquidation of the company in September 2018 rendered these investments worthless.
Atenolol is a beta blocker; that is, an antagonist of the β-adrenergic receptors. It is specifically a selective antagonist of the β1-adrenergic receptor with no intrinsic sympathomimetic activity (i.e., partial agonist activity) or membrane-stabilizing activity. However, the preferential action of atenolol is not absolute, and at high doses, it can also block β2-adrenergic receptors. Beta-blocking effects of atenolol include reduction in resting and exercise heart rate and cardiac output, reduction of systolic and diastolic blood pressure at rest and with exercise, inhibition of tachycardia induced by isoproterenol (a non-selective β-adrenergic receptor agonist), and reduction of reflex orthostatic tachycardia. The beta-blocking effects of atenolol, as measured by reduction of exercise-related tachycardia, are apparent within 1 hour and are maximal within 2 to 4 hours following a single oral dose. The general effects of atenolol, including beta-blocking and antihypertensive effects, last for at least 24 hours following oral doses of 50 or 100 mg. With intravenous administration, maximal reduction in exercise-related tachycardia occurs within 5 minutes and following a single 10 mg dose has dissipated within 12 hours. The duration of action of atenolol is dose-related and is correlated with circulating levels of atenolol.
In a clinical trial, the rate of systolic orthostatic hypotension was 21% versus 9% with placebo and the rate of diastolic orthostatic hypotension was 12% versus 4% with placebo in people with Parkinson's disease taking the ODT form of selegiline. The risk of hypotension is greater at the start of treatment and in the elderly (3% vs. 0% with placebo). The rate of hypotension or orthostatic hypotension with the selegiline patch was 2.2% versus 0.5% with placebo in clinical trials of people with depression. Significant orthostatic blood pressure changes (≥10 mm Hg decrease) occurred in 9.8% versus 6.7% with placebo, but most of these cases were asymptomatic and heart rate was unchanged. The rates of other orthostatic hypotension-related side effects in this population were dizziness or vertigo 4.9% versus 3.1% with placebo and fainting 0.5% versus 0.0% with placebo. It is said that orthostatic hypotension is rarely seen with the selegiline transdermal patch compared to oral MAOIs. Caution is advised against rapidly rising after sitting or lying, especially after prolonged periods or at the start of treatment, as this can result in fainting. Falls are of particular concern in the elderly. MAOIs like selegiline may lower blood pressure by increasing dopamine levels and activating dopamine receptors, by increasing levels of the false neurotransmitter octopamine, and/or by other mechanisms. Meta-analyses published in the 1990s found that the addition of selegiline to levodopa increased mortality in people with Parkinson's disease.
This has resulted in an egg-shaped planet, likely to be destroyed within 400 million years. 14 August The World Health Organization (WHO) declares mpox a public health emergency of international concern for the second time in two years, following the spread of the virus in African countries. Human ageing is found to progress in two accelerated bursts from the ages of 44 and 60, rather than being a gradual and linear process. 16 August – The Planetary Habitability Laboratory publishes a report concluding that the Wow! signal was likely caused by a rare astrophysical event, the sudden brightening of a cold molecular cloud triggered by a stellar emission. 22 August – The first systematic analysis of 1,500 climate policy measures from 41 countries is published. Of the policy interventions that have been tried by 2022, it identifies 63 successful ones in terms of large trend breaks. The authors find that the introduction of a right combination of measures is crucial and that price-based instruments played a key role in these policy mixes. 23 August – BNT116, the world's first mRNA lung cancer vaccine, begins a Phase I clinical trial in seven countries. 29 August – The first global analysis estimating inadequate intakes of 15 micronutrients using dietary intake data is published, suggesting over half of the global population do not consume enough iodine (68%), vitamin E (67%), calcium (66%), iron (65%), riboflavin (55%), folate (54%), and vitamin C (53%).
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.
Reversed-phase high-performance liquid chromatography with ultraviolet detection at 214 nanometres is the usual approach. Peak area percentage provides a purity figure relative to other components in the sample. Mass spectrometry is then applied to confirm identity.