This is a working overview of counter-ion, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-09-17. Anything still debated is marked as such rather than presented as settled.
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.
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.
Epitalon is a synthetic four-amino-acid peptide with the sequence alanine-glutamate-aspartate-glycine, commonly abbreviated AEDG. Its molecular formula is C14H22N4O9, and its calculated molar mass is approximately 390.35 grams per mole. The compound is a short fragment related to a peptide fraction isolated from bovine pineal gland extracts, and it is normally supplied as a lyophilised powder intended for laboratory research. It is not a registered pharmaceutical product in most countries.
The peptide emerged from research carried out in Saint Petersburg from the late 1980s onward, where investigators searched for shorter active fragments of a pineal preparation known as epithalamin. The name epitalon was chosen to reflect that parent extract. Early reports described effects on neuroendocrine markers and on the lifespan of laboratory animals. Much of that work appeared in Russian-language journals, with English translations following later, which affects how readily the original protocols can be assessed by outside groups.
| Property | Value | Notes |
|---|---|---|
| Identity confirmation | Electrospray or MALDI mass spectrometry | Observed mass compared with theoretical 390.35 Da |
| Purity specification | 95 percent or greater by RP-HPLC | Common convention for research-grade peptide |
| Counter-ion | Acetate or trifluoroacetate | Affects net peptide content of a weighed sample |
| Solution storage | −80 °C as single-use aliquots | Repeated freeze–thaw cycles accelerate loss |
| Main degradation route | Aspartimide formation at Asp-Gly | Produces isoaspartate and related species |
Animal and clinical reports appear mainly in Russian-language journals from the 1990s and 2000s, covering endpoints such as melatonin rhythm, lifespan in aged rodents, and retinal function. Many of these papers involve small groups, lack blinding or placebo comparison, and are difficult to retrieve through indexed databases. Review articles published in English generally summarise the claims without reanalysing the underlying data. Because no large randomised trial exists, the clinical importance of these reported effects stays unresolved and is properly described as an open question.
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.
Discussions in the literature often conflate three distinct entities: the pineal extract epithalamin, the isolated tetrapeptide AEDG, and commercial preparations sold under similar names. Reviews citing older Russian-language studies sometimes omit detail on purity, route of administration and control groups, which makes cross-study comparison difficult. Researchers working with the compound generally note the need for independent replication, standardized enzyme assays, and clearer reporting of peptide identity. These caveats are relevant when weighing claims that appear in secondary sources rather than in primary reports.
（TG:@pojiaai）Epitalon is a synthetic linear tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, abbreviated AEDG. It emerged from work on epithalamin, a peptide fraction prepared from bovine pineal tissue, and was designed as a short, chemically defined analogue of that extract. Early publications came mainly from Russian laboratories studying pineal peptides and aging-related endpoints. The compound appears in the literature under several spellings, including epithalon and epithalone, which complicates systematic searching. Its small size makes solid-phase assembly and routine analytical characterization straightforward.
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.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography with ultraviolet detection, frequently near 214 nanometers where the peptide bond absorbs. Mass spectrometry, most often with electrospray ionization, confirms the observed molecular mass and helps separate the intact peptide from truncated or modified forms. Amino acid analysis or tandem mass spectrometry can establish residue order. Purity is commonly quoted as an area percentage, yet such values are method-dependent, and comparisons between laboratories require matching column, gradient and detection wavelength.
Laboratory handling begins with dissolution of the lyophilized powder in water or a suitable aqueous buffer. The dry solid is the more stable form, so stock solutions are generally prepared only when required and kept cold afterwards. Repeated freezing and thawing of a solution is avoided because it encourages aggregation and gradual loss of the intact chain. Diluents and containers are selected to limit adsorption of a short peptide onto plastic surfaces and to reduce microbial growth in aqueous preparations.
Estrogens are metabolized via hydroxylation by cytochrome P450 enzymes such as CYP1A1 and CYP3A4 and via conjugation by estrogen sulfotransferases (sulfation) and UDP-glucuronyltransferases (glucuronidation). In addition, estradiol is dehydrogenated by 17β-hydroxysteroid dehydrogenase into the much less potent estrogen estrone. These reactions occur primarily in the liver, but also in other tissues.
==== Separation of unbound small molecules and ligand-protein complexes ==== Affinity selection is followed by the removal of unbound small molecules via ultrafiltration or size-exclusion chromatography, making only protein-bound ligands available for downstream analysis. Several types of ultrafiltration have been reported with varying degrees of throughput, including pressure-based, centrifugal, and precipitation-based ultrafiltration. Under both pressure-based and centrifugal formats, unbound small molecules are forced through a semipermeable membrane that excludes proteins on the basis of size. Multiple washing steps are required after ultrafiltration to ensure complete removal of unbound small molecules. Ultrafiltration can also be confounded by non-specific adsorption of unbound small molecules to the membrane. A group at the University of Illinois published a screening strategy involving amyloid-beta, in which ligands were used to stabilize the protein and prevent its aggregation. Ultrafiltration was used to precipitate aggregated amyloid-beta and remove unbound ligands, while the ligand-stabilized protein was detected and quantified using mass spectrometry. Size-exclusion chromatography (SEC) is more widely used in industrial drug discovery and has the advantage of more efficient removal of unbound compounds as compared to ultrafiltration. Size-exclusion approaches have been described in both high-performance liquid chromatography (HPLC) based and spin column formats.
== Analysis == The concentrations of individual compounds can be derived largely using the count rates of the precursor and product ions, and the reaction rate coefficients, k. Exothermic proton transfer reactions with H3O+ are assumed to proceed at the collisional rate (see Collision theory), the coefficient for which, kc, is calculable using the method described by Su and Chesnavich, providing the polarizability and dipole moment are known for the reactant molecule. NO+ and O2+ reactions proceed at kc less frequently, and thus the reaction rates of the reactant molecule with these precursor ions must often be derived experimentally by comparing the decline in the count rates of each of the NO+ and O2+ precursor ions to that of H3O+ as the sample flow of reactant molecules is increased. The product ions and rate coefficients have been derived in this way for well over 200 volatile compounds, which can be found in the scientific literature. The instrument can be programmed either to scan across a range of masses to produce a mass spectrum (Full Scan, FS, mode), or to rapidly switch between only the m/z values of interest (Multiple Ion Monitoring, MIM, mode). Due to the different chemical properties of the aforementioned precursor ions (H3O+, NO+, and O2+), different FS mode spectra can be produced for a vapor sample, and these can give different information relating to the composition of the sample. Using this information, it is often possible to identify the trace compound(s) that are present.
Sources: en.wikipedia.org
Elevated homocysteine levels, often due to mutations in the MTHFR gene, appear to increase the risk of vertebral artery dissection. People with an aneurysm of the aortic root and people with a history of migraine may be predisposed to vertebral artery dissection. Vascular tortuosity or redundancy in young patients is associated with an increased risk of spontaneous dissection.
== Government, law, and military == Captain of the Parish, a (now mainly ceremonial) appointment in the Isle of Man (post-nominal letters CP) Central Powers, a military alliance before and during World War I, led by the German Empire Certified Paralegal, an American legal qualification Charterparty, a maritime contract for the hire of a ship Civil parish, the lowest tier of government in England Command Post, in military terminology Commissioner of Police, the top-ranking officer of the Police Force Communist party, a political party that advocates communism through state policy Consejo popular, an electoral ward of Cuba Montenegrin Party (Crnogorska partija), a political party in Serbia
The traditions of British centenarians receiving greetings and congratulations was established by King Edward VII in 1908. The famous acrobat and tightrope walker Henry Johnson received a congratulatory letter from Edward VII via his royal courtier Viscount Knollys in 1906. The tradition of royal congratulations continued in 1908, when the secretary for King Edward VII sent a congratulatory letter to Reverend Thomas Lord of Horncastle, Lincolnshire, in a newspaper clipping, declaring, "I am commanded by the King to congratulate you on the attainment of your hundredth year, after a most useful life." The practice was formalised from 1917, under the reign of King George V, who also sent congratulations then sent by a telegram on the attainment of a diamond wedding anniversary (or jubilee) marking 60 years of marriage. During the reign of King George V, only 24 telegrams were sent; however, with the aging population, this increased to 273 during 1952, when Queen Elizabeth II ascended the throne. The Queen also sent a telegram, and later a portrait-style greeting card with the notation, "I am so pleased to know that you are celebrating your one hundredth birthday. I send my congratulations and best wishes to you on such a special occasion." Each few years the card was updated with a current updated picture of the Queen to ensure people did not receive the same card more than once. The Queen further sent her congratulations on one's 105th birthday and every year thereafter as well as on special wedding anniversaries.
The earliest description and illustration of gigantomastia dates to 1669. In July of that year the Plymouth physician William Durston wrote to the Royal Society, reporting the case of a patient named Elizabeth Travers. Durston's account was soon published in the Society's Philosophical Transactions, and includes the following account of the onset of symptoms:Elizabeth Treves, [sic] 23. or 24. years of age, fair of complexion, brown-hair'd, of an healthy constitution, low of stature, of honest repute, but of mean and poor parentage, near this Town [Plymouth], was on Friday July 3d, 1669 in good health, and went well to bed, where she took as good rest and sleep, as ever before, but in the morning, when she awaken'd, and attempted to turn herself in her bed, was not able, finding her Breasts so swell'd, that she was affrighted to an astonishment. Then endeavoring to sit up, the weight of her Breasts fastned her to her bed; where she hath layn ever since, yet without all pain and weakness either in her Breasts, or in any other part.Durston later wrote to the Society to report that Travers had died on October 21 of the same year, four months after the onset of enlargement. One breast removed after the woman's death weighed 64 lb (29 kg).
Sources: en.wikipedia.org
Mass spectrometry provides the identity check, because the observed mass is compared with the theoretical mass of the AEDG sequence. Chromatography separates and quantifies impurities but does not by itself prove which peptide is present. The two techniques are normally used together.
Yes. Trifluoroacetate and acetate ions remain associated with the peptide after purification, so a weighed quantity of powder contains less peptide than the nominal mass suggests. Certificates that report net peptide content rather than raw weight are more directly comparable between suppliers.
Dilute aqueous solutions are less stable than the dry powder and are usually aliquoted and frozen to avoid repeated freeze–thaw cycles. Lyophilised material is best stored desiccated at −20 °C, protected from light. Working solutions are typically prepared fresh from a frozen aliquot.
It is a synthetic tetrapeptide built from alanine, glutamate, aspartate and glycine. The four residues are joined by standard peptide bonds, giving a linear chain rather than a branched structure.