mass spectrometry raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-09-07 and is reviewed periodically as new material appears.
Stability of the tetrapeptide follows ordinary peptide chemistry rather than any unusual structural feature. The aspartate-glycine pair is prone to aspartimide formation under mildly basic or neutral conditions, and deamidation can follow, altering both mass and chromatographic retention. Dry lyophilised powder kept at or below minus twenty degrees Celsius is the usual handling recommendation, with repeated freeze-thaw cycles avoided. Once dissolved in neutral aqueous buffer, degradation proceeds over days to weeks depending on pH and temperature, while acidic conditions generally slow the aspartimide route. A formal stability-indicating study has not been published in the indexed literature.
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 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.
Epitalon is a synthetic tetrapeptide whose sequence is alanine–glutamate–aspartate–glycine, commonly abbreviated AEDG. It was developed in Russia during the 1980s and 1990s by investigators associated with the St. Petersburg Institute of Bioregulation and Gerontology, who studied short peptides as regulators of gene expression and tissue function. The alternative spelling epithalon appears interchangeably in the literature, and the two names refer to the same molecule. Outside Russia it is encountered chiefly as a research chemical rather than a licensed medicine, and it holds no approval from the United States Food and Drug Administration or the European Medicines Agency.
| 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 |
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.
Material supplied for laboratory use is normally a lyophilised white to off-white powder that dissolves readily in water and in isotonic saline. Lyophilised cakes are hygroscopic and should be equilibrated to room temperature before opening to limit condensation on the solid. Solutions are typically prepared at milligram-per-millilitre concentrations and divided into single-use aliquots, because repeated freeze–thaw cycles degrade short peptides. Aqueous solutions are far less stable than the dry powder, and identity is usually verified by mass spectrometry alongside purity estimation from reversed-phase high-performance liquid chromatography.
Epitalon is a synthetic linear tetrapeptide with the sequence alanine–glutamate–aspartate–glycine, abbreviated AEDG. Its molecular formula is C14H22N4O9 and the calculated mass is approximately 390.35 g/mol. The compound is made by solid-phase peptide synthesis rather than extracted from tissue, although early work described it as a short fragment of a peptide fraction obtained from bovine pineal extract. In the research literature the spelling epitalon and the variant epithalone both appear, while AEDG is the standard code used in peptide nomenclature.
Several names circulate for the same molecule, including epitalon, epithalone, epithalamin tetrapeptide, and the sequence code AEDG. A CAS registry number, 307297-39-8, is commonly cited for it, though catalogue entries should be checked against supplier documentation because mislabelled records occur. In its usual form the peptide carries free amino and carboxyl termini and is neither glycosylated nor lipidated. Researchers distinguish the defined tetrapeptide from epithalamin itself, a crude pineal preparation containing many peptides that is not chemically characterised.
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.
Documentation accompanying research peptides usually includes a certificate of analysis listing the batch number, purity figure, and test methods applied. Buyers comparing suppliers should check whether the reported purity refers to chromatographic area or to a mass-balance calculation, because the two are not equivalent. Counter-ion content, residual solvents, and water content are sometimes omitted from such certificates even though they affect the actual peptide mass present. Independent verification through a second laboratory is the most direct way to confirm that a supplied material matches its label.
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.
The compound is described in the literature as a derivative of epithalamin, a preparation obtained from bovine pineal tissue. Work on this peptide family was carried out mainly by a research group in Saint Petersburg beginning in the 1980s, and the substance was later registered for clinical use in Russia under the name Epitalon. Outside that region it is generally treated as a research chemical rather than an approved medicine. Statements about its biological activity rest on a relatively small number of studies, and independent replication remains limited.
Calcium ions are one type of second messengers and are responsible for many important physiological functions including muscle contraction, fertilization, and neurotransmitter release. The ions are normally bound or stored in intracellular components (such as the endoplasmic reticulum(ER)) and can be released during signal transduction. The enzyme phospholipase C produces diacylglycerol and inositol trisphosphate, which increases calcium ion permeability into the membrane. Active G-protein open up calcium channels to let calcium ions enter the plasma membrane. The other product of phospholipase C, diacylglycerol, activates protein kinase C, which assists in the activation of cAMP (another second messenger).
There is extensive experience, over many years, of the use of radioiodine in the treatment of thyroid overactivity, and this experience does not indicate any increased risk of thyroid cancer following treatment. However, a study from 2007 has reported an increased number of cancer cases after radioiodine treatment for hyperthyroidism. The principal advantage of radioiodine treatment for hyperthyroidism is that it tends to have a much higher success rate than medications. Depending on the dose of radioiodine chosen, and the disease under treatment (Graves' vs. toxic goiter, vs. hot nodule, etc.), the success rate in achieving definitive resolution of the hyperthyroidism may vary from 75 to 100%. A major expected side-effect of radioiodine in people with Graves' disease is the development of lifelong hypothyroidism, requiring daily treatment with thyroid hormone. On occasion, some people may require more than one radioactive treatment, depending on the type of disease present, the size of the thyroid, and the initial dose administered. People with Graves' disease manifesting moderate or severe Graves' ophthalmopathy are cautioned against radioactive iodine-131 treatment, since it has been shown to exacerbate existing thyroid eye disease. People with mild or no ophthalmic symptoms can mitigate their risk with a concurrent six-week course of prednisone. The mechanisms proposed for this side effect involve a TSH receptor common to both thyrocytes and retro-orbital tissue.
Vitamin E is fat soluble, so dietary supplement products are usually in the form of the vitamin, esterified with acetic acid to generate tocopheryl acetate, and dissolved in vegetable oil in a softgel capsule. For alpha-tocopherol, amounts range from 100 to 1000 IU per serving. Smaller amounts are incorporated into multi-vitamin/mineral tablets. Gamma-tocopherol and tocotrienol supplements are also available from dietary supplement companies. The latter are extracts from palm oil.
Navy shore bombardment and submarine operations. The Japanese increased their garrison in the north Kurils from 8,000 in 1943 to 41,000 in 1944 and maintained more than 400 aircraft in the Kurils and Hokkaido area in anticipation that the Americans might invade from Alaska.
Lowrie has played Sherlock Holmes in the radio drama series The Further Adventures of Sherlock Holmes on the program Imagination Theatre since 2001. He also voiced Holmes in the program's related radio series The Classic Adventures of Sherlock Holmes. He and Lawrence Albert, who voices Dr. Watson on the program, are the longest-running audio Holmes and Watson team in American radio history. In 2011, he published a science fiction novel titled Dancing with Eternity. An audiobook version narrated by Lowrie and McLain was released in April 2014. In 2021, Lowrie directed a livestreamed version of the play 'night, Mother starring his wife Ellen McLain and Sheila Houlahan on the online platform Twitch with the story adapted by McLain within the context of the COVID-19 pandemic. The filmed online play is performed through an online face-to-face chat with the screen split between McLain's and Houlahan's screens, occasionally interrupted by cuts to pre-filmed footage relevant to the story. Lowrie has also had small roles in several live-action films, most notable of which being the 2025 critically acclaimed period drama Train Dreams as a foreman overlooking the construction of a railroad for the Spokane International Railway (credited as Mr. Sears).
Sources: en.wikipedia.org
(CH2CH2)O + H2S → HO–CH2CH2–HS 2 (CH2CH2)O + H2S → (HO–CH2CH2)2S (CH2CH2)O + RHS → HO–CH2CH2–SR The excess of ethylene oxide with an aqueous solution of hydrogen sulfide leads to the tris-(hydroxyethyl) sulfonyl hydroxide:
==== Laboratory ==== Lysergic acid is generally produced by hydrolysis of natural lysergamides, but can also be synthesized in the laboratory by a complex total synthesis, for example by Robert Burns Woodward's team in 1956. An enantioselective total synthesis based on a palladium-catalyzed domino cyclization reaction has been described in 2011 by Fujii and Ohno. Lysergic acid monohydrate crystallizes in very thin hexagonal leaflets when recrystallized from water. Lysergic acid monohydrate, when dried (140 °C at 2 mmHg or 270 Pa) forms anhydrous lysergic acid.
where ∆(APB) is the area of triangle APB. Denote the segments that the diagonal intersection P divides diagonal AC into as AP = p1 and PC = p2, and similarly P divides diagonal BD into segments BP = q1 and PD = q2. Then the quadrilateral is tangential if and only if any one of the following equalities are true:
Rather than finding homologous proteins from different species, a new Tag/Catcher pair was developed from SpyTag/SpyCatcher with minimal mutations. SpyTag I3W (AW) reacts with SpyCatcher F77V, F94A (BVA) but minimally with SpyCatcher, whereas SpyCatcher F77V, F94A can react with both SpyTag I3W and SpyTag. However, the cross-reactivity of SpyCatcher F77V, F94A with both SpyTag versions may limit its utility as a new Tag/Catcher pair. A different chemistry can be exploited for protein ligation: the discovery of an intramolecular ester bond formation in Clostridium perfringens cell-surface adhesin protein Cpe0147 led to the development of another Tag/Catcher pair with Cpe0147565–587 as the Tag and Cpe0147439–563 as the Catcher. The ester bond formed between Thr-Gln is irreversible, however by mutating the Thr to Ser, the Ser-Gln ester bond is reversible with a change of pH.
Edith died on 29 November 1971, at the age of 82. Ronald returned to Oxford, where Merton College gave him convenient rooms near the High Street. He missed Edith, but enjoyed being back in the city. Tolkien was made a Commander of the Order of the British Empire in the 1972 New Year Honours and received the insignia of the Order at Buckingham Palace on 28 March 1972. In the same year Oxford University gave him an honorary Doctorate of Letters. He was further awarded an honorary Doctorate of Letters from the University of Edinburgh on 22 July 1973. He had the name Luthien [sic] engraved on Edith's tombstone at Wolvercote Cemetery, Oxford. When Tolkien died 21 months later on 2 September 1973 from a bleeding ulcer and chest infection, at the age of 81, he was buried in the same grave, with "Beren" added to his name. Tolkien's will was proven on 20 December 1973, with his estate valued at £190,577 (equivalent to £2,991,790 in 2026).
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.
Epitalon is a synthetic four-amino-acid peptide with the sequence alanine–glutamate–aspartate–glycine, also written AEDG. It was developed in Russian gerontology research and is studied for proposed effects on telomerase, melatonin regulation, and neuroendocrine function. It is not an approved pharmaceutical in the United States or the European Union.