The short version of counterion fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-05-08 and is reviewed periodically as new material appears.
The four residues give epitalon a molecular formula of C14H22N4O9 and a molecular weight near 390.35 daltons. The presence of two acidic residues, glutamate and aspartate, makes the free peptide strongly acidic, while the alanine and glycine ends provide neutral, nonpolar character. This combination produces a molecule with substantial water solubility. Because there are no cysteine, methionine, or tryptophan residues, the peptide lacks the most common oxidation-sensitive side chains, which simplifies handling compared with many longer peptides.
The proposed relationship between epitalon and pineal function is a central part of its background. Khavinson's group reported that short peptides corresponding to regions of larger pineal proteins could influence gene expression in cells. Epitalon was framed as a synthetic analogue of an active fragment rather than a direct isolation product. Whether the tetrapeptide reproduces the effects of the parent extract is an open question, because comparative studies are limited and the parent extract itself is not a single defined substance.
Peptides of this size are generally stable as dry solids but degrade in solution over time. The principal routes are hydrolysis of the peptide backbone and oxidation, with hydrolysis favoured by elevated temperature and extreme pH. Aqueous solutions held at room temperature can show measurable loss of purity within days, while frozen aliquots are considerably more durable. Because the sequence contains neither cysteine nor methionine, oxidation is less of a concern than for many other peptides, but pH control during handling still matters.
Typical storage for the lyophilized powder is −20 °C or lower, in a sealed container protected from light and moisture. Hygroscopic material should be allowed to equilibrate to room temperature before the vial is opened, which limits condensation on the contents. Working solutions are commonly divided into single-use aliquots and frozen to avoid repeated freeze-thaw cycles. Dilute solutions are more prone to adsorption onto plastic surfaces and to loss during filtration, so procedures that minimize transfers and use low-binding labware are preferable.
Reversed-phase high-performance liquid chromatography is the standard approach for assessing purity, usually with ultraviolet detection near 214 nm, where the peptide bond absorbs. Mass spectrometry, most often with electrospray ionization, confirms the molecular mass and helps reveal truncation or deletion byproducts. Amino acid analysis can verify composition, and counterion content is sometimes measured because peptides purified with trifluoroacetic acid retain variable amounts of that salt. Purity figures reported without a stated method and detection wavelength are difficult to interpret.
| Property | Value | Notes |
|---|---|---|
| Amino acid sequence | Ala-Glu-Asp-Gly | Tetrapeptide, often abbreviated AEDG |
| Molecular formula | C14H22N4O9 | Free peptide, unmodified termini |
| Molecular weight | ~390.35 Da | Calculated for the free acid form |
| Appearance | White to off-white powder | Typical lyophilized product form |
| Solubility class | Freely soluble in water | Two acidic residues dominate ionic character |
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.
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.
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.
Solubility is high in water, phosphate-buffered saline and normal saline, a pattern that follows from the two acidic residues in the chain. The peptide dissolves poorly in non-polar solvents such as hexane or chloroform. Stock solutions are often prepared in water first and then diluted into the buffer of interest. Because the molecule is small and hydrophilic, filtration through a low-protein-binding membrane is usually straightforward, and visible particulates are uncommon in freshly made solutions.
== See also == List of organs of the human body Hydrostatic weighing Dietary element Composition of blood List of human blood components Body composition Abundance of elements in Earth's crust Abundance of the chemical elements
=== United States === In the 2 July 2026 issue of Federal Register (21 FR 1308), the federal government of the United States (through the Administrator of the Drug Enforcement Administration) issued a notice of intent to publish a temporary order to schedule three 7-hydroxymitragynine-related substances (mitragynine pseudoindoxyl, MGM-15, and MGM-16) under Schedule I of the Controlled Substances Act. On August 25, 2026, the DEA placed MGM-15 in Schedule I through an emergency temporary scheduling order, making unauthorized possession, manufacture, and distribution illegal.
=== Others === Blood: Pentamidine frequently causes leukopenia and less often thrombopenia, which may cause symptomatic bleeding. Some cases of anemia, possibly related to folic acid deficiency, have been described. Cardiovascular: Hypotension, which may be severe. Severe or fatal arrhythmias and heart failure are quite frequent. Kidney: 25 percent develop signs of nephrotoxicity ranging from mild, asymptomatic azotemia (increased serum creatinine and urea) to irreversible renal failure. Ample fluids or intravenous hydration may prevent some nephrotoxicity. Liver: Elevated liver enzymes are associated with intravenous use of pentamidine. Hepatomegaly and hepatitis have been encountered with long term prophylactic use of pentamidine inhalation. Neurological: Dizziness, drowsiness, neuralgia, confusion, hallucinations, seizures and other central side effects are reported. Pancreas: Hypoglycemia that requires symptomatic treatment is frequently seen. On the other hand, pentamidine may cause or worsen diabetes mellitus. Respiratory: Cough and bronchospasm, most frequently seen with inhalation. Skin: Severe local reactions after extravasculation of intravenous solutions or following intramuscular injection treatment have been seen. Pentamidine itself may cause rash, or rarely Stevens–Johnson syndrome or Lyell syndrome. Eye discomfort, conjunctivitis, throat irritation, splenomegaly, Herxheimer reaction, electrolyte imbalances (e.g. hypocalcemia).
Sources: en.wikipedia.org
==== Binding of escitalopram to human SERT protein ==== Andersen et al. were able to generate a model of the (S)-citalopram binding site in human SERT by combining mutational analysis and comparative modeling where they found out that Asn-177 and Phe-341 where key determinants for (S)-citalopram potency and high affinity inhibition in addition to Tyr-95, Asp-98, Ile-172 and Ser438 previously described, where three functional groups of the inhibitors structure bind to the transporters amino acids. (S)-citalopram is positioned as that the cyanophthalane-. fluorophenyl- and methylaminoprpyl moieties occupy three different sub-pockets within the SERT binding pocket. Ile-172 and Phe-341 are likely not in direct contact with the drug molecule, but they are very important for controlling alignment of the inhibitor.
== Interactions based on pharmacodynamics == Pharmacodynamic interactions are the drug–drug interactions that occur at a biochemical level and depend mainly on the biological processes of organisms. These interactions occur due to action on the same targets; for example, the same receptor or signaling pathway.
This article outlines United States-related events which occurred in the year 2021. The COVID-19 pandemic continued to heavily impact the US, with the emergence of numerous COVID-19 variants leading to a substantial rise in both infections and deaths across the country. Though Donald Trump lost his bid to be re-elected president of the United States to former vice president Joe Biden, Trump's attempts to overturn the 2020 United States presidential election have continued throughout the year. On January 6, a minority of pro-Trump protestors stormed the Capitol building and temporarily halted the formal counting of electoral votes in Congress. 2021 was additionally defined by protests against COVID-19 lockdowns in response to the pandemic, as well as the beginning of a period of high inflation and ongoing protests mostly against police brutality. The year also saw an extremely active Atlantic hurricane season, a destructive wildfire season in California, and a power crisis in Texas.
Sources: en.wikipedia.org
=== Fish === Lungs are found in three groups of fish; the coelacanths, the bichirs and the lungfish. Like in tetrapods, but unlike fish with swim bladder, the opening is at the ventral side of the oesophagus. The coelacanth has a nonfunctional and unpaired vestigial lung surrounded by a fatty organ. Bichirs, the only group of ray-finned fish with lungs, have a pair which are hollow unchambered sacs, where the gas-exchange occurs on very flat folds that increase their inner surface area. The lungs of lungfish show more resemblance to tetrapod lungs. There is an elaborate network of parenchymal septa, dividing them into numerous respiration chambers. In the Australian lungfish, there is only a single lung, albeit divided into two lobes. Other lungfish, however, have traditionally been considered having two lungs, but newer research defines paired lungs as bilateral lung buds that arise simultaneously and are both connected directly to the foregut, which is only seen in tetrapods. In all lungfish, including the Australian, the lungs are located in the upper dorsal part of the body, with the connecting duct curving around and above the oesophagus. The blood supply also twists around the oesophagus, suggesting that the lungs originally evolved in the ventral part of the body, as in other vertebrates.
=== Etymology === Obesity is from the Latin obesitas, which means "stout, fat, or plump". Ēsus is the past participle of edere (to eat), with ob (over) added to it. The Oxford English Dictionary documents its first usage in 1611 by Randle Cotgrave.
==== Psychosis ==== Isotretinoin has also been linked to psychosis. Many of the side effects of isotretinoin mimic hypervitaminosis A, which has been associated with psychotic symptoms. The dopamine hypothesis of schizophrenia and psychosis suggests that an increase in dopaminergic stimulation or sensitivity in the limbic system causes psychotic symptoms. It has been suggested that dysregulation of retinoid receptors by retinoids such as isotretinoin may cause schizophrenia. The evidence for this is threefold: transcriptional activation of the dopamine D2 receptor – in addition to serotonin and glutamate receptors – is regulated by retinoic acid; schizophrenia and the retinoid cascade have been linked to the same gene loci; and retinoid dysfunction causes congenital anomalies identical to those observed in people with schizophrenia. Further, the expression of dopamine receptors has indeed been shown to be regulated by retinoic acid.
Sources: en.wikipedia.org
Epitalon is a synthetic tetrapeptide composed of four amino acids: alanine, glutamate, aspartate, and glycine. It is written as Ala-Glu-Asp-Gly. The free peptide has a molecular weight of about 390 daltons and is normally supplied as a lyophilized powder.
No. Epitalon is chemically synthesized, not extracted. It was designed as a short synthetic fragment conceptually related to larger pineal peptides studied in the same research tradition, particularly the extract known as epithalamin. The two are distinct materials with different compositions.
The term bioregulator is used in this research tradition for short peptides proposed to influence gene expression or cell function. Epitalon is grouped with other synthetic short peptides under this label. The term reflects a proposed mechanism rather than an established drug classification.
The powder is normally kept at −20 °C or below in a sealed, moisture-protected container. Letting the vial reach room temperature before opening helps prevent condensation on the contents.