If you have been reading about counterion 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 2025-10-10. Where a claim depends on a specific study, the study is described rather than over-claimed.
Dissolution is usually performed in water or a suitable aqueous buffer, and the resulting liquid is divided into single-use portions before freezing. Freeze-thaw cycling is a recognised source of loss for short peptides, since each cycle can encourage aggregation or adsorption onto container walls. Working solutions are generally kept cold and used within a short window, although published stability data specific to epitalon are thin. Containers should be marked with concentration and date, and solutions examined for cloudiness before use.
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.
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 |
|---|---|---|
| Sequence | Ala-Glu-Asp-Gly | Written in three-letter amino acid code |
| Single-letter code | AEDG | Form used in most catalogue entries |
| Typical purity specification | 95 percent or higher | Value read from the HPLC chromatogram |
| Storage, dry solid | Minus 20 degrees Celsius, desiccated | Sealed container, protected from light |
| Handling, solution | Divide into single-use portions | Limits losses from freeze-thaw cycling |
Identity and purity are established with reversed-phase high-performance liquid chromatography and mass spectrometry. The chromatogram shows the main peak and any truncated or oxidised by-products, while the mass spectrum confirms the expected 390 dalton mass. Amino acid analysis can corroborate composition when a sample's origin is uncertain. Counterion content, particularly residual trifluoroacetate from purification, is frequently reported alongside purity because it shifts the net mass of the solid.
Reference material is normally supplied as a lyophilised powder in a sealed vial. Product literature typically recommends storage at minus twenty degrees Celsius or colder, protected from light and moisture. Freeze-thaw cycling is usually avoided because repeated condensation can introduce water into the vial. Working solutions are commonly prepared fresh, aliquoted, and kept cold for short periods rather than stored at ambient temperature. Labelling the date of opening helps track how long a vial has been in use.
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.
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.
TCM is said to be based on such texts as Huangdi Neijing (The Inner Canon of the Yellow Emperor), and Compendium of Materia Medica, a sixteenth-century encyclopedic work, and includes various forms of herbal medicine, acupuncture, cupping therapy, gua sha, massage (tui na), bonesetter (die-da), exercise (qigong), and dietary therapy. TCM is widely used in the Sinosphere. One of the basic tenets is that the body's qi is circulating through channels called meridians having branches connected to bodily organs and functions. There is no evidence that meridians or vital energy exist. Concepts of the body and of disease used in TCM reflect its ancient origins and its emphasis on dynamic processes over material structure, similar to the humoral theory of ancient Greece and ancient Rome. The demand for traditional medicines in China is a major generator of illegal wildlife smuggling, linked to the killing and smuggling of endangered animals. The Chinese authorities have engaged in attempts to crack down on illegal TCM-related wildlife smuggling.
=== Dietary challenges === Adhering to the GFD can negatively impact those with coeliac disease, requiring major changes for an individual and their family. The restrictive nature of the GFD can lead to no longer enjoying food and pressure to be constantly vigilant about diet. The social life of those with coeliac disease is also negatively affected by the GFD. Cross-contamination—gluten-free food coming into contact with gluten—is a common worry for those eating away from home. Eating out may cause anxiety as it requires disclosing dietary restrictions and risking potential cross-contamination. Receiving a diagnosis of coeliac disease and the dietary changes required to manage the disorder can affect a person's relationship with food and lead to disordered eating as well as anxiety and depression. A diagnosis of coeliac disease can carry stigma, which may affect individuals' ability to seek help or disclose their condition when needed. Accessing gluten-free food can be a burden due to limited availability and variety, as well as higher costs compared to gluten-containing foods. Over the past ten years, the costs of gluten-free food have decreased; however, it remains significantly more expensive than gluten-containing food. There has been an increase in the popularity of the GFD among those without coeliac disease, which has improved the availability of gluten-free foods.
== Education == Weber attended Case Western Reserve University, receiving his BA in Chemistry and Biology in 1970. He then worked with Irving Sunshine at the Cuyahoga County Coroner’s Office, in the Forensic Toxicology group. After enlisting in the U.S. Navy, he helped to establish a drug analysis lab in the Great Lakes Naval Hospital at the Great Lakes Naval Station. He returned to university in 1974. For his doctorate, Weber worked with William Purdy, first at the University of Maryland and then at McGill University. He received his Ph.D. from McGill University in 1979. His research at McGill involved the development of an electrochemical immunoassay using an electrochemical detector.
). The question raised but not answered by this study was whether the illness caused subtle immune deficiency that led to reactivation of HHV-6, or whether reactivation of HHV-6 led to the symptoms of the illness. Subsequent studies employing only serological techniques that do not distinguish active from latent infection have produced mixed results: most, but not all, have found an association between CFS and HHV-6 infection. Other studies have employed assays that can detect active infection: primary cell culture, PCR of serum or plasma, or IgM early antigen antibody assays. The majority of these studies have shown an association between CFS and active HHV-6 infection, although a few have not. In summary, active infection with HHV-6 is present in a substantial fraction of patients with CFS. Moreover, HHV-6 is known to infect cells of the nervous system and immune system, organ systems with demonstrable abnormalities in CFS. Despite this association, it remains unproven that reactivated HHV-6 infection is a cause of CFS.
=== Train of four ratio test === The train of four ratio (i.e., ToFr) is a neuromuscular test for monitoring neuromuscular function (see monitoring neuromuscular blockade). In this test, a peripheral nerve (most commonly the ulnar nerve) is stimulated by an electrical impulse 4 times (i.e., T1, T2, T3, T4) and the strength of contraction is measured in a muscle(s) (i.e., the abductor pollicis longus and brevis muscles for the ulnar nerve). The ratio of the amplitude of muscle contraction in response to the fourth impulse (T4) divided by the amplitude of muscle contraction in response to the first impulse is calculated. The ratio of these two contractions should be 1.0. Values less than this are regarded as abnormal. ToFr is used to determine when the effects of an administered neuromuscular-blocking drug have worn off (see postoperative residual curarization) or as the most objective, accurate, and sensitive test for determining the presence and severity of myasthenia gravis: myasthenia gravis is considered to afflict the tested muscle if its ToFr ratio (i.e., T4/T1) is less than 0.9.
Sources: en.wikipedia.org
=== Early life and education === Martin Litchfield West was born on 23 September 1937 at Eltham General Hospital (Eltham, London), the elder child (there being a younger daughter, Dr Jennifer Bywaters) of civil engineer Maurice Charles West and Catherine Baker, née Stainthorpe. His parents lived at that time in Orpington, but moved in 1939 to Hampton, where his father was appointed resident engineer at the Metropolitan Water Board-operated waterworks. West's father's family were from the Home Counties, and his mother's family from Yorkshire and Durham. His paternal grandfather, Robert West, lectured in electrical engineering; his maternal grandfather, John Stainthorpe, was a railwayman from Pickering. Litchfield was the maiden name of his paternal grandmother. Aged four, West entered the private preparatory school of Denmead. At 11, he lost a scholarship at Colet Court (now St Paul's Juniors), but was offered a feepaying place instead. West discovered at Colet his interest in languages and invented at 14 a competitor of Esperanto he labelled 'Unilingua'. In 1951, he won a scholarship to the main school, St Paul's. Excelling at both linguistics and mathematics, he was advanced to the 'Upper Eighth' and sat for a scholarship to Balliol College a year early. His tutors included Donald Russell, Michael Stokes and Russell Meiggs. Among his peers were future Nobel Prize winner Anthony J. Leggett, and future Permanent Secretary Peter Gregson.
from arginine via nitric oxide synthase, as a byproduct of the production of nitric oxide for signaling purposes from ornithine through the breakdown of proline or glutamine/glutamate from asymmetric dimethylarginine via DDAH Citrulline is made from ornithine and carbamoyl phosphate in one of the central reactions in the urea cycle. It is also produced from arginine as a byproduct of the reaction catalyzed by NOS family (NOS; EC 1.14.13.39). It is also prevalent in trichohyalin at the inner root sheath and medulla of hair follicles, where it is synthesized from arginine. Arginine is first oxidized into N-hydroxyl-arginine, which is then further converted to citrulline concomitant with release of nitric oxide.
Hallucinogen antidotes such as the atypical antipsychotics risperidone, quetiapine, and olanzapine are trip killers that are used to block the effects of mescaline and other hallucinogenic drugs. Atypical antipsychotics are serotonin 5-HT2A receptor antagonists that directly block the effects of hallucinogens. The serotonin 5-HT2A receptor antagonist ketanserin has been found to block the psychoactive effects of mescaline. Similarly, the antipsychotic chlorpromazine, which acts as both a dopamine D2 receptor antagonist and to a lesser extent as a serotonin 5-HT2A receptor antagonist, has been reported to reverse the psychoactive effects of mescaline. Other phenothiazines, such as promethazine and diethazine, have also been reported to antagonize the effects of mescaline in humans, whereas prochlorperazine was much less effective and promazine was ineffective. Barbiturates, which are GABAA receptor positive allosteric modulators, have been found to reduce the anxiety induced by mescaline.
The frequency of the SNP differed significantly by race, partly explaining observed differences in response to interferon therapy between European-Americans and African-Americans. Unconfirmed results suggested that interferon eye drops may be an effective treatment for people who have herpes simplex virus epithelial keratitis, a type of eye infection. There is no clear evidence to suggest that removing the infected tissue (debridement) followed by interferon drops is an effective treatment approach for these types of eye infections. Unconfirmed results suggested that the combination of interferon and an antiviral agent may speed the healing process compared to antiviral therapy alone. When used in systemic therapy, IFNs are mostly administered by an intramuscular injection. The injection of IFNs in the muscle or under the skin is generally well tolerated. The most frequent adverse effects are flu-like symptoms: increased body temperature, feeling ill, fatigue, headache, muscle pain, convulsion, dizziness, and hair thinning. IFN treatment has been associated with neuropsychiatric adverse effects such as depression, anxiety, irritability, and sleep disturbance. Local injection site reactions, particularly erythema, pain, and induration, are also frequently observed. IFN therapy causes immunosuppression, in particular through neutropenia, and can result in some infections manifesting in unusual ways.
==== Effects on striatal dopamine ==== While caffeine does not directly bind to any dopamine receptors, it influences the binding activity of dopamine at its receptors in the striatum by binding to adenosine receptors that have formed GPCR heteromers with dopamine receptors, specifically the A1–D1 receptor heterodimer (this is a receptor complex with one adenosine A1 receptor and one dopamine D1 receptor) and the A2A–D2 receptor heterotetramer (this is a receptor complex with two adenosine A2A receptors and two dopamine D2 receptors). The A2A–D2 receptor heterotetramer has been identified as a primary pharmacological target of caffeine, primarily because it mediates some of its psychostimulant effects and its pharmacodynamic interactions with dopaminergic psychostimulants. Caffeine also causes the release of dopamine in the dorsal striatum and nucleus accumbens core (a substructure within the ventral striatum), but not the nucleus accumbens shell, by antagonizing A1 receptors in the axon terminal of dopamine neurons and A1–A2A heterodimers (a receptor complex composed of one adenosine A1 receptor and one adenosine A2A receptor) in the axon terminal of glutamate neurons. During chronic caffeine use, caffeine-induced dopamine release within the nucleus accumbens core is markedly reduced due to drug tolerance.
Sources: en.wikipedia.org
== Domain == The C1q domain is a conserved protein domain. C1q is a subunit of the C1 enzyme complex that activates the serum complement system. C1q comprises 6 A, 6 B and 6 C chains. These share the same topology, each possessing a small, globular C-terminal domain, a collagen-like Gly/Pro-rich central region, and a conserved C-terminal region, the C1q domain. The C1q protein is produced in collagen-producing cells and shows sequence and structural similarity to collagens VIII and X.
== Epidemiology == Systemic scleroderma is a rare disease, with an annual incidence that varies in different populations. Estimates of incidence (new cases per million people) range from 3.7 to 43 in the United Kingdom and Europe, 7.2 in Japan, 10.9 in Taiwan, 12.0 to 22.8 in Australia, 13.9 to 21.0 in the United States, and 21.2 in Buenos Aires. The interval of peak onset starts at age 30 and ends at age 50. Globally, estimates of prevalence vary from 31.0 to 658.6 affected people per million. Systemic sclerosis has a female:male ratio of 3:1 (8:1 in mid- to late childbearing years). Incidence is twice as high among African Americans. Full-blooded Choctaw Native Americans in Oklahoma have the highest prevalence in the world (469 per 100,000). The disease has some hereditary association. It may also be caused by an immune reaction to a virus (molecular mimicry) or by toxins.
=== Use in radioisotope thermoelectric generators === Beginning on January 1, 1957, Mound Laboratories RTG inventors Jordan & Birden were working on an Army Signal Corps contract (R-65-8- 998 11-SC-03-91) to conduct research on radioactive materials and thermocouples suitable for the direct conversion of heat to electrical energy using polonium-210 as the heat source. In 1961, Capt. R. T. Carpenter had chosen 238Pu as the fuel for the first RTG (radioisotope thermoelectric generator) to be launched into space as auxiliary power for the Transit IV Navy navigational satellite. By January 21, 1963, the decision had yet to be made as to what isotope would be used to fuel the large RTGs for NASA programs. Early in 1964, Mound Laboratories scientists developed a different method of fabricating the weapon component that resulted in a production efficiency of around 98%. This made available the excess Savannah River 238Pu production for Space Electric Power use just in time to meet the needs of the SNAP-27 RTG on the Moon, the Pioneer spacecraft, the Viking Mars landers, more Transit Navy navigation satellites (precursor to today's GPS) and two Voyager spacecraft, for which all of the 238Pu heat sources were fabricated at Mound Laboratories. The radioisotope heater units were used in space exploration beginning with the Apollo Radioisotope Heaters (ALRH) warming the Seismic Experiment placed on the Moon by the Apollo 11 mission and on several Moon and Mars rovers, to the 129 LWRHUs warming the experiments on the Galileo spacecraft.
== History == Ziprasidone is chemically similar to risperidone, of which it is a structural analogue. It was first synthesized in 1987 at the Pfizer central research campus in Groton, Connecticut. Phase I trials started in 1995. In 1998 ziprasidone was approved in Sweden. After the FDA raised concerns about long QT syndrome, more clinical trials were conducted and submitted to the FDA, which approved the drug on February 5, 2001.
Sources: en.wikipedia.org
Reversed-phase high-performance liquid chromatography is run alongside mass spectrometry. The chromatogram separates components and gives a purity figure, while the mass spectrum confirms that the measured molecular mass matches the expected sequence. Neither measurement on its own is treated as sufficient.
Long-term holding is usually at minus twenty degrees Celsius in a sealed, desiccated container. A refrigerator is adequate for short intervals before use. Light exposure is normally avoided as well. Allowing a cold container to warm before opening reduces moisture condensation on the contents.
Repeated cycles are generally avoided. Each freeze and thaw can promote aggregation or loss of peptide to container surfaces, which reduces the amount available for later work. Dividing a solution into single-use portions at the outset is the usual way to limit this problem.
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.