If you have been reading about HPLC purity 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 2026-05-05. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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 |
|---|---|---|
| Amino acid sequence | Ala-Glu-Asp-Gly | Linear tetrapeptide, also written AEDG |
| Molecular mass | About 390.35 g/mol | Value calculated from the sequence |
| Appearance | White to off-white powder | Lyophilised material forms a loose cake |
| Solubility | Freely soluble in water | Also dissolves in isotonic saline |
| Storage | -20 °C, desiccated | Aliquot solutions to avoid freeze–thaw cycling |
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.
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 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.
=== Sleep === Nicotine reduces the amount of rapid eye movement (REM) sleep, slow-wave sleep (SWS), and total sleep time in healthy nonsmokers given nicotine via a transdermal patch, and the reduction is dose-dependent. Acute nicotine intoxication has been found to significantly reduce total sleep time and increase REM latency, sleep onset latency, and non-rapid eye movement (NREM) stage 2 sleep time. Depressive non-smokers experience mood and sleep improvements under nicotine administration; however, subsequent nicotine withdrawal has a negative effect on both mood and sleep.
United Kingdom In the United Kingdom, transfusion medicine is a sub-speciality of hematology. Serious Hazards of Transfusion (SHOT) collects and analyses reports of adverse events related to transfusion, aiming to improve patient safety. Its reports have led to wider training for medical staff in the UK and a central reporting scheme to allow errors to be reported. There is the Better Blood Continuing Education Programme, which is organised by the EUB which is part of the SNBTS. The EUB consists of many specialist healthcare professionals. The programme's aim is to improve transfusion medicine practise. The programme is reviewed each annually in January. In the UK, there are restrictions in place to decrease the risk of the transmission of Creutzfeldt–Jakob disease.
== Further reading == Muir T. W.; Sondhi D.; Cole P. A. (1998). "Expressed protein ligation: A general method for protein engineering". Proc. Natl. Acad. Sci. USA. 95 (12): 6705–6710. Bibcode:1998PNAS...95.6705M. doi:10.1073/pnas.95.12.6705. PMC 22605. PMID 9618476. Nilsson B. L.; Soellner M. B.; Raines R. T. (2005). "Chemical synthesis of proteins". Annu. Rev. Biophys. Biomol. Struct. 34: 91–118. doi:10.1146/annurev.biophys.34.040204.144700. PMC 2845543. PMID 15869385. Kent S. B. H. (2009). "Total chemical synthesis of proteins". Chemical Society Reviews. 38 (2): 338–351. doi:10.1039/B700141J. PMID 19169452. S2CID 5432012. Conibear A. C.; Watson E. E.; Payne R. J.; Becker C. F. W. (2018). "Native chemical ligation in protein synthesis and semi-synthesis". Chemical Society Reviews. 47 (24): 9046–9068. doi:10.1039/c8cs00573g. hdl:2123/22610. PMID 30418441.
=== Lipids === An indication of the role of high-density lipoprotein (HDL) on atherosclerosis has been with the rare Apo-A1 Milano human genetic variant of this HDL protein. A small short-term trial using bacterial-synthesized human Apo-A1 Milano HDL in people with unstable angina produced a fairly dramatic reduction in measured coronary plaque volume in only six weeks vs. the usual increase in plaque volume in those randomized to placebo. The trial was published in JAMA in early 2006. Ongoing work starting in the 1990s may lead to human clinical trials—probably by about 2008. These may use synthesized Apo-A1 Milano HDL directly, or they may use gene-transfer methods to pass the ability to synthesize the Apo-A1 Milano HDLipoprotein. Methods to increase HDL particle concentrations, which in some animal studies largely reverse and remove atheromas, are being developed and researched. However, increasing HDL by any means is not necessarily helpful. For example, the drug torcetrapib is the most effective agent currently known for raising HDL (by up to 60%). However, in clinical trials, it also raised deaths by 60%. All studies regarding this drug were halted in December 2006. The actions of macrophages drive atherosclerotic plaque progression. Immunomodulation of atherosclerosis is the term for techniques that modulate immune system function to suppress this macrophage action.
Long-term risks include mania and heart issues such as long QT syndrome, and potentially fatal interactions with other drugs. Only two randomized controlled trials have been conducted on ibogaine and noribogaine for substance use disorders, and while they show preliminary anti-addictive potential, their safety and efficacy are unconfirmed, with significant risks including cardiotoxicity and fatalities. Ibogaine is federally illegal in the United States. It is used in treatment clinics abroad under legal gray areas, with growing media attention. It has inspired the development of non-hallucinogenic, non-cardiotoxic analogues like 18-MC and tabernanthalog for therapeutic use. In 2025, Texas allocated $50 million for clinical research on ibogaine to develop FDA-approved treatments for opioid use disorder, co-occurring substance use disorders, and other ibogaine-responsive conditions. A 2026 US executive order directed federal agencies to accelerate review of ibogaine.
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Botox is usually injected in the three lip elevator muscles that converge on the lateral side of the ala of the nose; the levator labii superioris (LLS), the levator labii superioris alaeque nasi muscle (LLSAN), and the zygomaticus minor (ZMi). In 2025 there were 19,701 professionals administering botox in the United Kingdom, an increase of 437% since 2023. There was a similar increase in the USA.
God bless you." At one point, Singh executed 18 people on one day; these 18 people were among the 58 rioters who killed four prison officers while they were serving their jail terms in a Pulau Senang island prison in 1963. Singh also said that he has hanged seven people within 90 minutes; these seven men were the culprits of the 1971 Gold Bars triple murders, in which a businessman and illegal gold trader was killed together with his driver and colleague over a total of 120 gold bars. Executions peaked between 1994 and 1998; Singapore had the second highest per-capita execution rate in the world during this period, estimated by the United Nations to be 13.83 executions annually per one million people, just behind Turkmenistan with 14.92. Since then, executions have become far less common, with some years having no executions at all. For example, no one was executed in 2012 and 2013, and two persons were executed in 2014. Nevertheless, in the late 2010s, the number of executions has started to increase again: in 2018, 13 people were executed, the most since at least 2003. and four people (including two unreported executions) were hanged in 2019. No one has been executed from the start of 2020 to August 2020, due to the COVID-19 pandemic in Singapore. The first person to be sentenced to death during the COVID-19 pandemic in Singapore was Punithan Genasan, a 37-year-old Malaysian who was also the first to be sentenced to death on 15 May 2020 via a remote court hearing on Zoom. Punithan, who was convicted of drug trafficking, was later acquitted on 31 October 2022 upon appeal.
==== Analysis ==== Analysis of banded chromosomes is done at a microscope by a clinical laboratory specialist in cytogenetics (CLSp(CG)). Generally 20 cells are analyzed which is enough to rule out mosaicism to an acceptable level. The results are summarized and given to a board-certified cytogeneticist for review, and to write an interpretation taking into account the patient's previous history and other clinical findings. The results are then given out reported in an International System for Human Cytogenetic Nomenclature 2009 (ISCN2009)..
This reaction is exploited in native chemical ligation, a protocol for peptide synthesis. In a related reaction, thioesters can be converted into esters. Thioacetate esters can also be cleaved with methanethiol in the presence of stoichiometric base, as illustrated in the preparation of pent-4-yne-1-thiol:
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== Biological functions == Besides being a structural receptor, integrin α2β1 is a signaling receptor which receives signals from the extracellular medium to the intracellular part of the cell. Integrin α2β1 controls the process of cell migration. The process of cell migration takes place during embryogenesis, wound healing, and tissue remodeling. In these cases, the cells have to move through the extracellular matrix in a controlled manner. The interaction between α2β1 integrin and collagen functions in the migration of cells by creating focal adhesion that are specialized protein structures which assist in connecting actin filament of the cytoskeleton to the extracellular matrix. The receptor has a role in intracellular signaling pathway that regulate cell proliferation, cellular differentiation, and survival. It activates the signal molecules such as FAK, Src family of kinases, phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK). All these processes contribute to gene expression, reorganization of the cytoskeleton, and response to environmental cues. These functions allow α2β1 in the regulation of normal tissue homeostasis and repair and adaptation of the cells to the changes in the environment provided by the extracellular matrix. Integrin α2β1 is involved in the process of hemostasis as the integrin facilitates the adhesion of platelets to exposed collagen at sites of vascular damage. The receptor is also important to the immune system functioning.
Criterion 1: Generalized joint hypermobility, as measured by the Beighton score Criterion 2: Minimum two of the following must be met: Symptoms that suggest a difference in connective tissue structure Unusually soft or velvety skin Mild skin hyperextensibility Unexplained striae distensae or rubae at the back, groins, thighs, breasts, and/or abdomen in adolescents, men, or pre-pubertal women without a history of significant gain or loss of body fat or weight Bilateral piezogenic papules of the heel Recurrent or multiple abdominal hernia(s) Atrophic scarring involving at least two sites and without the formation of truly papyraceous and/or hemosideric scars as seen in classical EDS Pelvic floor, rectal, and/or uterine prolapse in children, men, or nulliparous women without a history of morbid obesity or other known predisposing medical condition Dental crowding and a high or narrow palate Arachnodactyly Arm span-to-height ratio ≥1.05 Mitral valve prolapse (MVP) mild or greater based on strict echocardiographic criteria Aortic root dilatation with Z-score >+2 Positive family history Proof that these symptoms interfere with daily life Musculoskeletal pain in two or more limbs, recurring daily for at least 3 months Chronic, widespread pain for ≥3 months Recurrent joint dislocations or frank joint instability, in the absence of trauma Criterion 3: Exclusion of all other possible connective tissue disorders that may be the root cause of symptoms.
For research purposes, curium is obtained by irradiating not uranium but plutonium, which is available in large amounts from spent nuclear fuel. A much higher neutron flux is used for the irradiation that results in a different reaction chain and formation of 244Cm:
Sources: en.wikipedia.org
It is a synthetic tetrapeptide. Its sequence was derived from research on peptide fractions of bovine pineal extract, and the intact AEDG sequence has not been demonstrated as an abundant free peptide in human tissue.
AEDG is the one-letter code for the four amino acids alanine, glutamate, aspartate and glycine in that order. The same molecule is written in three-letter form as Ala-Glu-Asp-Gly.
Identity is normally confirmed by mass spectrometry against the calculated mass of roughly 390.35 g/mol. Purity is then estimated by reversed-phase high-performance liquid chromatography with ultraviolet detection.
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.