A practical reference on Tetrapeptide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-01-21 and is reviewed periodically as new material appears.
Epitalon is a synthetic tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, abbreviated AEDG. Its molecular formula is C14H22N4O9 and its calculated monoisotopic mass is approximately 390.35 daltons. The compound does not occur naturally as a free peptide; it is produced by solid-phase peptide synthesis. Because it contains two acidic residues and no basic residues, the neutral form carries a net negative charge at physiological pH. This charge profile influences how the peptide behaves in solution and during chromatographic analysis.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C14H22N4O9 | Free acid form of the tetrapeptide |
| Molecular mass | About 390.35 Da | Calculated monoisotopic value |
| Appearance | White to off-white powder | Typical lyophilized presentation |
| Solubility | Soluble in water | Also dissolves in buffered saline |
| Storage temperature | Minus 20 degrees Celsius | Dry, dark conditions; avoid repeated thawing |
Epitalon is a synthetic tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, commonly abbreviated AEDG. It was designed at the St. Petersburg Institute of Bioregulation and Gerontology as a short, chemically defined analogue of epithalamin, a fraction obtained from bovine pineal tissue. Small peptide bioregulators of this type formed a long-running line of work there from the 1980s onward. Because the molecule is produced by solid-phase synthesis rather than extraction, its composition is exact and its purity can be measured directly.
The most frequently cited proposed action is induction of telomerase, the enzyme that adds repeat sequences to chromosome ends. Cell-culture work from the originating group reported higher telomerase reverse transcriptase expression and measurable telomere elongation in human somatic cells after exposure. How a four-residue peptide would reach nuclear gene regulation is not established, and no cell-surface receptor or uptake route has been identified. Additional reports describe changes in melatonin secretion, antioxidant enzyme activity and lipid peroxidation in aged animals, but these findings remain mechanistically unconnected to the telomerase observation.
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.
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.
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.
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.
Contrary to popular belief, however, the library does not retain all of these works in its permanent collection, although it does add an average of 12,000 items per day. Rejected items are used in trades with other libraries around the world, distributed to federal agencies, or donated to schools, communities, and other organizations within the United States. The legal requirement of mandatory deposit was challenged in Valancourt Books v. Garland, with the court finding that requiring a publisher to deposit copies of its books at the Library of Congress was a violation of the Takings Clause. As is true of many similar libraries, the Library of Congress retains copies of every publication in the English language that is deemed significant. The Library of Congress states that its collection fills about 838 mi (1,349 km) of bookshelves and holds more than 167 million items with over 39 million books and other print materials. A 2000 study by information scientists Peter Lyman and Hal Varian suggested that the amount of uncompressed textual data represented by the 26 million books then in the collection was 10 terabytes. The library also administers the National Library Service for the Blind and Physically Handicapped, an audio book and braille library program provided to more than 766,000 Americans.
== See also == Drug design Drug metabolism Microbial biodegradation Biodegradation Bioremediation Antioxidant SPORCalc, an example process for exploring xenobiotic and drug metabolism databases Archived 2009-03-18 at the Wayback Machine
Pharmacokinetics is the study of the bodily absorption, distribution, metabolism, and excretion of drugs. When describing the pharmacokinetic properties of the chemical that is the active ingredient or active pharmaceutical ingredient, pharmacologists are often interested in L-ADME:
Sources: en.wikipedia.org
Physical activity can be related to a person's professional activities, non-work related daily activities like walking or cycling, or it can be in the form of activities such as recreation or team sports. The specific type of activity can be tailored to populations such as children, pregnant women, and elderly adults. Tailored activity to one's fitness level also encourages the body to heal properly and prevent any injuries as a result of exercise. Physical inactivity leads to less energy expenditure and is a factor that impacts obesity rates in both children and adults. Physical inactivity has become a worldwide concern since inactivity also elevates the risk of heart disease. With a regular active lifestyle it can reduce the risk for noncommunicable diseases like diabetes, heart disease, and dyslipidemia (high cholesterol). Physical activity not only reduces the risk of noncommunicable diseases, but it also can benefit the body such as improving sleep patterns, reducing both anxiety and depression, and of course, helps weight loss and weight management.
=== Implantable devices === The development of implantable devices like pacemakers and spinal cord stimulators also began in the mid-20th century. Devices to manage pain received FDA (USA) approval in the late 1960s. In 1967, Dr. Norm Shealy from Western Reserve Medical School presented "the first dorsal column stimulator for pain control". It was developed based on the Gate Theory of Wall and Melzack, which stated that pain transmissions from tiny nerve fibers would be blocked if competing transmissions were made along larger sensory nerve fibers. In 1973, Prof Hosbuchi reported relieving the denervation facial pain of anesthesia dolorosa via lasting electrical stimulation of the somatosensory thalamus, which marked the beginning of the age of deep-brain stimulation. In 1987, the team of neurosurgeons/neurologists Professor Benabid and Professor Pollak and their colleagues (Grenoble, France) published results on this topic about thalamic Deep Brain Stimulation. Deep brain stimulation began to be used to treat motor symptoms of movement disorders such as Parkinson's disease. In 1989, the International Neuromodulation Society (INS) was founded in Paris after the first International Congress on Epidural Spinal Cord Stimulation in Groningen, the Netherlands, by a select group of physicians: Dr. Augustinsson, a Swedish neurosurgeon; Dr. Galley, a French cardiologist; Dr. Illis, a British neurologist; Dr. Kranick, a German neurosurgeon: Dr. Meglio, an Italian Neurosurgeon; Dr. Sier, a Dutch vascular surgeon and Dr. Staal, a Dutch neurosurgeon.
Cases were reported where mental symptoms were alleviated following the surgical removal of diseased or damaged brain tissue. The accumulation of medical case studies on behavioural changes following damage to the frontal lobes led to the formulation of the concept of Witzelsucht, which designated a neurological condition characterised by a certain hilarity and childishness in those with the condition. The picture of frontal lobe function that emerged from these studies was complicated by the observation that neurological deficits attendant on damage to a single lobe might be compensated for if the opposite lobe remained intact. In 1922, the Italian neurologist Leonardo Bianchi published a detailed report on the results of bilateral lobectomies in animals that supported the contention that the frontal lobes were both integral to intellectual function and that their removal led to the disintegration of the subject's personality. This work, while influential, was not without its critics due to deficiencies in experimental design. The first bilateral lobectomy of a human subject was performed by the American neurosurgeon Walter Dandy in 1930. The neurologist Richard Brickner reported on this case in 1932, relating that the recipient, known as "Patient A", while experiencing a blunting of affect, had no apparent decrease in intellectual function and seemed, at least to the casual observer, perfectly normal. Brickner concluded from this evidence that "the frontal lobes are not 'centers' for the intellect".
Sources: en.wikipedia.org
Pushing Cool: Big Tobacco, Racial Marketing, and the Untold Story of the Menthol Cigarette (2021) excerpt Werner, Carl Avery. Tobaccoland: A book about tobacco; its history, legends, literature, cultivation, social and hygienic influences, commercial development, industrial processes and governmental regulation. (1922) online Winkler, John K. Tobacco tycoon, the story of James Buchanan Duke (1942) online Woofter Jr. T.J. The Plight of Cigarette Tobacco (1931) Zhou, Xun Yu, Gilman, Sander L. (2004). Smoke: a global history of smoking. London: Reaktion Books. ISBN 978-1-86189-200-3.
retinal + NAD+ + H2O → retinoic acid + NADH + H+ Retinoic acid is actively transported into the cell nucleus by CRABp2 where it regulates thousands of genes by binding directly to gene targets via retinoic acid receptors. In addition to retinol, retinal and retinoic acid, there are plant-, fungi- or bacteria-sourced carotenoids which can be metabolized to retinol, and are thus vitamin A vitamers. There are also what are referred to as 2nd, 3rd and 4th generation retinoids which are not considered vitamin A vitamers because they cannot be converted to retinol, retinal or all-trans-retinoic acid. Some are prescription drugs, oral or topical, for various indications. Examples are etretinate, acitretin, adapalene, bexarotene, tazarotene and trifarotene.
Britain gathered allies to form the Third Coalition against The French Empire after Napoleon was self-proclaimed as emperor. In response, Napoleon seriously considered an invasion of Great Britain, massing 180,000 troops at Boulogne. Before he could invade, he needed to achieve naval superiority—or at least to pull the British fleet away from the English Channel. A complex plan to distract the British by threatening their possessions in the West Indies failed when a Franco-Spanish fleet under Admiral Villeneuve turned back after an indecisive action off Cape Finisterre on 22 July 1805. The Royal Navy blockaded Villeneuve in Cádiz until he left for Naples on 19 October; the British squadron caught and overwhelmingly defeated a Franco-Spanish fleet in the Battle of Trafalgar on 21 October (the British commander, Lord Nelson, died in the battle). Napoleon never again had the opportunity to challenge the British at sea, nor to threaten an invasion. He again turned his attention to the enemies on the Continent.
=== Oxidative half === In the oxidative half of the mechanism, Cys63 nucleophilically attacks the nearest sulfide unit in the GSSG molecule (promoted by His467), which creates a mixed disulfide bond (GS-Cys58) and a GS− anion. His467 of GSR then protonates the GS- anion to release the first molecule of GSH. Next, Cys63 nucleophilically attacks the sulfide of Cys58, releasing a GS− anion, which, in turn, picks up a solvent proton and is released from the enzyme, thereby creating the second GSH. So, for every GSSG and NADPH, two reduced GSH molecules are gained, which can again act as antioxidants scavenging reactive oxygen species in the cell.
Sources: en.wikipedia.org
Epitalon is a synthetic tetrapeptide built from four amino acids: alanine, glutamate, aspartate, and glycine. It is not extracted from a natural source but made in the laboratory by chemical synthesis. Its short length makes it relatively straightforward to produce at high purity.
No naturally occurring free form of the peptide has been described. The four-amino-acid sequence can appear as a fragment within larger proteins, but that is not the same as the intact compound being present as a circulating molecule. Materials used in research are synthetic.
Purity is usually checked by reverse-phase high-performance liquid chromatography, which separates the target peptide from related impurities. Mass spectrometry is commonly used alongside it to confirm molecular mass. Some suppliers also provide amino acid analysis for additional sequence confirmation.
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.