The short version of reversed-phase HPLC fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-06-30. Anything still debated is marked as such rather than presented as settled.
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.
Most experimental work has been carried out in cell culture and animal models. Several reports describe changes in telomerase activity and proliferation in cultured cells, while rodent studies have examined lifespan, melatonin rhythm and reproductive endpoints. Human data remain limited, and much of the published clinical material consists of small trials with incomplete reporting of methods and controls. Whether the cell and animal findings translate into measurable effects in people is an open question, and the mechanistic basis of the reported telomerase changes is not fully established.
Identity and purity of epitalon samples are normally established by reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres, combined with mass spectrometry. The mass spectrum confirms the expected molecular ion and can reveal truncated or oxidised by-products. Amino acid analysis after acid hydrolysis verifies that the four residues are present in the expected ratio. Certificates typically report a purity figure taken from chromatographic peak area, expressed as a percentage of total integrated signal.
Lyophilised epitalon is generally held at minus twenty degrees Celsius in a sealed container kept dry and dark. Cooler conditions are sometimes recommended for long-term archives. The solid takes up moisture readily enough that repeated opening of a vial introduces water, so dividing a batch into smaller portions before storage lowers degradation risk. Aqueous solutions are less durable than the dry powder and are usually prepared shortly before use, then kept cold and shielded from light to slow hydrolysis and oxidation.
Verification of research-grade material involves comparing a supplier chromatogram against an in-house reference, checking the observed mass against the calculated value, and where possible confirming residue order by tandem mass spectrometry or enzymatic peptide mapping. Purity claims should be read alongside the method used to obtain them, because detection wavelength and integration settings alter the result. Batch-specific data, rather than a generic grade statement, is the informative part of a certificate.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Linear tetrapeptide | Four residues joined by three peptide bonds |
| Sequence | Ala-Glu-Asp-Gly | Commonly abbreviated AEDG |
| Molecular formula | C14H22N4O9 | Free acid form |
| Monoisotopic mass | Approximately 390 Da | Matches values reported from mass spectrometry |
| Net charge near neutral pH | Negative | Contributed by glutamate and aspartate side chains |
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.
Verification of a sample usually begins with reversed-phase high-performance liquid chromatography, which resolves the peptide from truncated sequences and other impurities and expresses purity as a percentage of total peak area. Mass spectrometry by electrospray ionisation or matrix-assisted laser desorption supplies an independent check, because the measured mass can be compared against the theoretical value for AEDG. Amino acid analysis or tandem mass spectrometry sequencing can confirm residue order. Each of these methods answers a different question: a purity figure does not establish identity, and an identity match does not establish how much of the material is intact peptide.
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.
After his abdication on 14 December 1918, Ukrainian hetman Pavlo Skoropadskyi emigrated to Germany. From there he led the so-called Hetman movement (Ukrainian: Гетьманський рух), which consisted of a number of Ukrainian conservative monarchist organizations from different groups of Ukrainian diaspora. Most prominent of these organizations were the Ukrainian Union of Agrarians-Statists (Ukrainian: Український союз хліборобів-державників) founded in Vienna by Vyacheslav Lypynskyi and Serhiy Shemet, and the United Hetman Organization (Ukrainian: Союз гетьманців державників) active in Canada and the United States. In his "Letters to Brothers Agrarians", published in 1926, Lypynskyi elaborated the idea of an independent, classocratic, pan-Ukrainian "toilers' monarchy" without political parties, ruled by hetman and his dynasty with the help of an agrarian aristocracy and the co-operation of the productive classes. In Canada and the United States the Hetman movement emerged from the pre-WW1 Sich scouting societies and was implicitly supported by the Ukrainian Greek-Catholic Church. The movement supported the re-establishment of the Hetman state of Pavlo Skoropadskyi and devoted a lot of energy to military training of Ukrainian émigrés for the future liberation of their homeland, going as far as to acquire a number of airplanes. In 1940 the Canadian branch of the organization became one of the founders of the Ukrainian Canadian Congress.
Thus, it may serve to sequester potentially toxic metal ions, protecting the rest of the cell. This hypothesis is supported by the fact that the loss of neuromelanin, observed in Parkinson's disease, is accompanied by an increase in iron levels in the brain.
Significant efforts have been focused on the mechanisms responsible for Aβ production, including the proteolytic enzymes gamma- and β-secretases which generate Aβ from its precursor protein, APP (amyloid precursor protein). Aβ circulates in plasma, cerebrospinal fluid (CSF) and brain interstitial fluid (ISF) mainly as soluble Aβ40. Amyloid plaques contain both Aβ40 and Aβ42, while vascular amyloid is predominantly the shorter Aβ40. Several sequences of Aβ were found in both lesions. Increases in either total Aβ levels or the relative concentration of both Aβ40 and Aβ42 (where the former is more concentrated in cerebrovascular plaques and the latter in neuritic plaques) have been implicated in the pathogenesis of both familial and sporadic Alzheimer's disease. Due to its more hydrophobic nature, the Aβ42 is the most amyloidogenic form of the peptide. However the central sequence KLVFFAE is known to form amyloid on its own, and probably forms the core of the fibril.
Sources: en.wikipedia.org
Be in the region of the binding energy curve where a fission chain reaction is possible (i.e., above radium) Have a high probability of fission on neutron capture Release more than one neutron on average per neutron capture. (Enough of them on each fission, to compensate for non-fissions and absorptions in non-fuel material) Have a reasonably long half-life Be available in suitable quantities.
When a crystalline aqueous suspension of steroid is administered via intramuscular injection, a crystalline depot suspended in fluid is formed locally within the muscle. These crystals slowly dissolve and the steroid is gradually absorbed into the body, resulting in the long durations of such preparations. Particle sizes of 10 μm or less have no apparent depot effect. A larger needle size is needed for aqueous suspensions of steroids to allow the steroid crystals to pass through the needle lumen. Aqueous suspensions pose a risk of injection site reactions such as local irritation, swelling, and redness, with often severe pain. The reactions are worse with larger crystal sizes. Particle sizes of more than 300 μm in the case of estradiol benzoate have been found to be too painful for use. The local injection site reactions, which do not occur with oil solutions, have limited the clinical use of aqueous suspensions of estradiol and its esters as well as other steroids.
Hemolymph or haemolymph is a body fluid that circulates inside arthropod bodies transporting nutrients and oxygen to tissues, comparable to blood in vertebrates. It is composed of a plasma in which circulating immune cells called hemocytes are dispersed in addition to many plasma proteins (hemoproteins) and dissolved chemicals. It is the key component of the open circulatory system characteristic of arthropods such as insects, arachnids, myriapods and crustaceans. Some non-arthropod invertebrates such as molluscs and annelids also possess a similar hemolymphatic circulatory system. In insects, the largest arthropod clade, the hemolymph mainly carries nutrients but not oxygen, which is supplied to the tissues separately by direct deep ventilation through an extensive tracheal system. In other arthropods, oxygen is dissolved into the hemolymph from gills, book lungs or across the cuticle and then distributed to the body tissues via the hemocoel.
Sources: en.wikipedia.org
It is a synthetic tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, often abbreviated AEDG. The molecule is linear and contains no modified residues, so it is fully described by its sequence.
The compound came out of work on epithalamin, a peptide preparation derived from pineal tissue, conducted largely in Russian laboratories. Later studies in other countries examined it mainly in cell cultures and animal models.
The tetrapeptide sequence is a synthetic construct rather than a described circulating peptide. It was derived by analogy to peptide fractions obtained from tissue extracts, not isolated from blood or tissue as such.
The usual approach is reversed-phase HPLC with ultraviolet detection, reported as a percentage of total peak area. Mass spectrometry is used alongside chromatography to confirm identity rather than purity alone.