If you have been reading about reversed-phase HPLC 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 2025-12-31. Where a claim depends on a specific study, the study is described rather than over-claimed.
Published evidence comes mainly from Russian-language journals and from a single research group, with small sample sizes and limited independent replication. A few laboratories outside that group have examined related peptides and reported weaker or absent telomerase effects, so the central claim is best described as contested rather than settled. Rodent studies report modest changes in some ageing markers and in survival, but designs vary and control conditions are often sparse. No large randomised trial in humans has been published, and long-term safety data in healthy populations are correspondingly thin.
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.
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.
No pharmacopoeial monograph exists for this peptide, so quality rests on the supplier's internal specifications and on whatever independent testing a purchaser arranges. Certificates of analysis differ widely in which tests they report and in the limits applied. The counter-ion introduced during purification, commonly acetate or trifluoroacetate, changes the net peptide content of a given mass of powder, so two samples of equal weight may not contain equal amounts of the active sequence. Third-party laboratories can verify purity, identity, residual solvents, and counter-ion content for a fee, which makes documentation more informative than labelling.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C14H22N4O9 | Calculated from the four residues with three water losses |
| Molecular mass | About 390.35 g/mol | Monoisotopic mass near 390.14, used for mass-spectrometric identification |
| Peptide sequence | Ala-Glu-Asp-Gly | Single-letter form AEDG; no disulfide bonds or modified residues |
| Appearance | White to off-white solid | Supplied as a dried powder |
| Isoelectric point | Around 4 | Estimated from aspartate and glutamate side-chain pKa values |
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.
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.
Sildenafil protects cyclic guanosine monophosphate (cGMP) from degradation by cGMP-specific phosphodiesterase type 5 (PDE5) in the corpus cavernosum. Nitric oxide (NO) in the corpus cavernosum of the penis binds to guanylate cyclase receptors, which results in increased levels of cGMP, leading to smooth muscle relaxation (vasodilation) of the intimal cushions of the helicine arteries. This smooth muscle relaxation leads to vasodilation and increased inflow of blood into the spongy tissue of the penis, causing an erection. Robert F. Furchgott, Ferid Murad, and Louis Ignarro won the Nobel Prize in Physiology or Medicine in 1998 for their independent study of the metabolic pathway of nitric oxide in smooth muscle vasodilation. The molecular mechanism of smooth muscle relaxation involves the enzyme CGMP-dependent protein kinase, also known as PKG. This kinase is activated by cGMP and it phosphorylates multiple targets in the smooth muscle cells, namely myosin light chain phosphatase, RhoA, IP3 receptor, phospholipase C, and others. Overall, this results in a decrease in intracellular calcium and desensitizing proteins to the effects of calcium, engendering smooth muscle relaxation. Sildenafil is a potent and selective inhibitor of cGMP-specific phosphodiesterase type 5 (PDE5), which is responsible for degradation of cGMP in the corpus cavernosum. The molecular structure of sildenafil is similar to that of cGMP and acts as a competitive binding agent of PDE5 in the corpus cavernosum, resulting in more cGMP and increased penile response to sexual stimulation.
=== ZMapp === A 2014 paper described how Mapp and its collaborators, including investigators at Public Health Agency of Canada, Kentucky BioProcessing, and the National Institute of Allergy and Infectious Diseases, first chimerized the three antibodies comprising ZMAb, then tested combinations of MB-003 and the chimeric ZMAb antibodies in guinea pigs and then primates to determine the best combination, which turned out to be c13C6 from MB-003 and two chimeric mAbs from ZMAb, c2G4 and c4G7. This is ZMapp. In an experiment also published in the 2014 paper, 21 rhesus macaque primates were infected with the Kikwit Congolese variant of EBOV. Three primates in the control arm were given a non-functional antibody, and the 18 in the treatment arm were divided into three groups of six. All primates in the treatment arm received three doses of ZMapp, spaced 3 days apart. The first treatment group received its first dose on 3rd day after being infected; the second group on the 4th day after being infected, and the third group, on the 5th day after being infected. All three primates in the control group died; all 18 primates in the treatment arm survived. Mapp then went on to show that ZMapp inhibits replication of a Guinean strain of EBOV in cell cultures. Mapp remains involved in the production of the drug through its contracts with Kentucky BioProcessing, a subsidiary of Reynolds American.
=== Graphite oxide reduction === P. Boehm reported producing monolayer flakes of reduced graphene oxide in 1962. Rapid heating of graphite oxide and exfoliation yields highly dispersed carbon powder with a few percent of graphene flakes. Another method is the reduction of graphite oxide monolayer films, e.g. by hydrazine with annealing in argon/hydrogen with an almost intact carbon framework that allows efficient removal of functional groups. Measured charge carrier mobility exceeded 1,000 cm/Vs (10 m/Vs). Burning a graphite oxide coated DVD produced a conductive graphene film (1,738 siemens per meter) and specific surface area (1,520 square meters per gram) that was highly resistant and malleable. A dispersed reduced graphene oxide suspension was synthesized in water by a hydrothermal dehydration method without using any surfactant. The approach is facile, industrially applicable, environmentally friendly, and cost-effective. Viscosity measurements confirmed that the graphene colloidal suspension (graphene nanofluid) exhibits Newtonian behavior, with the viscosity showing a close resemblance to that of water.
=== Acute inflammation === When there is a stimulus, the CRP level can increase 10,000-fold from less than 50 μg/L to more than 500 mg/L. Its concentration can increase to 5 mg/L by 6 hours and peak at 48 hours. The plasma half-life of CRP is 19 hours, and is constant in all medical conditions. Therefore, the only factor that affects the blood CRP concentration is its production rate, which increases with inflammation, infection, trauma, necrosis, malignancy, and allergic reactions. Other inflammatory mediators that can increase CRP are TGF beta 1, and tumor necrosis factor alpha. In acute inflammation, CRP can increase as much as 50 to 100 mg/L within 4 to 6 hours in mild to moderate inflammation or an insult such as skin infection, cystitis, or bronchitis. It can double every 8 hours and reaches its peak at 36 to 50 hours following injury or inflammation. CRP between 100 and 500 mg/L is considered highly predictive of inflammation due to bacterial infection. Once inflammation subsides, CRP level falls quickly because of its relatively short half-life.
Sources: en.wikipedia.org
== History == Phenibut was synthesized at the A. I. Herzen Leningrad Pedagogical Institute (USSR) by Professor Vsevolod Perekalin's team and tested at the Institute of Experimental Medicine, USSR Academy of Medical Sciences. It was introduced into clinical use in Russia in the 1960s.
This region is as extensive as the Amazon basin but has a very different climate as it lies farther south at a higher altitude. In the interior northeast, seasonal rainfall is even more extreme. South of Bahia, near the coasts, and more southerly most of the state of São Paulo, the distribution of rainfall changes, with rain falling throughout the year. The south enjoys subtropical conditions, with cool winters and average annual temperatures not exceeding 18 °C (64.4 °F); winter frosts and snowfall are not rare in the highest areas. The semiarid climatic region generally receives less than 800 millimeters (31.5 in) of rain, most of which generally falls in a period of three to five months of the year and occasionally less than this, creating long periods of drought. Brazil's 1877–78 Grande Seca (Great Drought), the worst in Brazil's history, caused approximately half a million deaths. A similarly devastating drought occurred in 1915. In 2024, for the first time, "a drought has covered all the way from the North to the country's Southeast". It is the strongest drought in Brazil since the beginning of measurement in the 1950s, covering almost 60% of the country's territory. The drought is linked to deforestation and climate change.
With a decreasing number of mothers who breast-feed, more infants become obese children as they grow up and are reared on infant formula instead. Fewer children go outside and engage in active play as technology, such as television and video games, keeps children indoors. Rather than walking or biking to a bus-stop or directly to school, more school-age children are driven to school by their parents, reducing physical activity. As family sizes decrease, the children's pester power, their ability to force adults to do what they want, increases. This ability enables them to have easier access to calorie-packed foods, such as candy and soda drinks. The social context around family meal-time plays a role in rates of childhood obesity.
The accepted treatment for affected boys presenting with the cerebral childhood form of the disease is a bone marrow transplant, a procedure which carries significant risks. However, because most affected males will demonstrate adrenal insufficiency, early discovery and treatment of this symptom could potentially prevent complications and allow these patients to be monitored for other treatment in the future, depending on the progression of their disease. The Loes score is a rating of the severity of abnormalities in the brain found on MRI. It ranges from 0 to 34, based on a point system derived from the location and extent of disease and the presence of atrophy in the brain, either localized to specific points or generally throughout the brain. A Loes score of 0.5 or less is classified as normal, while a Loes score of 14 or greater is considered severe. It was developed by neuroradiologist Daniel J. Loes MD and is an important tool in assessing disease progression and the effectiveness of therapy.
== Computational studies of protein folding == Computational studies of protein folding includes three main aspects related to the prediction of protein stability, kinetics, and structure. A 2013 review summarizes the available computational methods for protein folding.
Sources: en.wikipedia.org
Narcolepsy Depression Anxiety Obsessive–compulsive disorder Attention deficit hyperactivity disorder (ADHD) and its three subtypes. Juvenile chronic arthritis Postural orthostatic tachycardia syndrome (PoTS) Ehlers–Danlos syndromes Angelman syndrome
== History == It was published in 1950 by Blakiston. Creator and editor Tinsley Harrison's quotation appeared on the first edition of this book in 1950: No greater opportunity or obligation can fall the lot of a human being than to be a physician. In the care of suffering he needs technical skill, scientific knowledge and human understanding. He who uses these with courage, humility and wisdom will provide a unique service to his fellow man and will build an enduring edifice of character within himself. The physician should ask of his destiny no more than this and he should be content with no less. Blakiston was acquired by McGraw-Hill in 1954. The 17th edition of the textbook is dedicated to George W. Thorn, who was editor of the first seven editions of the book and editor in chief of the eighth edition. He died in 2004. The 18th edition of the book (ISBN 978-0071748896) was edited by Anthony Fauci, Dennis Kasper, Stephen Hauser, J. Larry Jameson and Joseph Loscalzo. New chapters added include "Systems Biology in Health and Disease," "The Human Microbiome," "The Biology of Aging," and "Neuropsychiatric Illnesses in War Veterans." The 19th edition of the book was edited by Dennis Kasper, Anthony Fauci, Stephen Hauser, Dan Longo, J. Larry Jameson and Joseph Loscalzo. AL.com in December 2014 wrote that it was still "a best-selling internal medicine text in the United States and around the world," and that it had been reprinted 16 times and translated into 14 languages. The 20th edition of the book, edited by Dennis Kasper, Anthony Fauci, Stephen Hauser, Dan Longo, J.
== Literature == Carl-Gerd Dieris: Zur Frage der Luminiszenz von thermooxidativ geschädigten Polycarpolaktam. Eine neue Synthese des Bakterienfarbstoffes Indigoidin und seiner Tetra-N-alkylderivate. 1980. Hans Günter Schlegel: Allgemeine Mikrobiologie. Thieme Verlagsgruppe, Stuttgart 1992, ISBN 978-3-13-444607-4. Reverchon, Sylvie; Rouanet, Carine; Expert, Dominique; Nasser, William (2002-01-02). "Characterization of Indigoidine Biosynthetic Genes in Erwinia chrysanthemi and Role of This Blue Pigment in Pathogenicity". Journal of Bacteriology. 184 (3): 654–665. doi:10.1128/JB.184.3.654-665.2002. PMC 139515. PMID 11790734. Christin Schönfeld: Charakterisierung und biochemische Analyse der Indigoidin Synthease BpsA aus S. lavendulae ATCC 11924. Masterarbeit, Philipps-Universität Marburg 2012. M. Müller, S. Ausländer, D. Ausländer, C. Kemmer, M. Fussenegger: A novel reporter system for bacterial and mammalian cells based on the non-ribosomal peptide indigoidine. Metabolic Engineering 14/2012, S. 325–335 (doi:10.1016/j.ymben.2012.04.002). H. Kobayashi, Y. Nogi, K. Hirokoshi: New violet 3,3'-bipyridyl pigment purified from deep-sea microorganism Shewanella violacea DSS12. In: Extremophiles Nr. 11(2)/2012, S. 245–250. PMID 17102923.
== Awards == 1988 Du Vigneaud Award for Young Investigators in Peptide Research 1989 Protein Society Young Investigator Award 1992 Eli Lilly Award in Biological Chemistry 1993 DuPont Merck Summit Award 1995 Fellow, American Association for the Advancement of Science 1998 Fellow, AAAS 1999 Member, National Academy of Sciences (U.S.A.) 2003 The American Peptide Society Merrifield Award 2008 The American Chemical Society Ralph F. Hirschmann Award in Peptide Chemistry 2009 The American Peptide Society Makineni Award 2015 The Stein & Moore Award of the Protein Society 2016 Weizmann Institute Max Perutz Memorial Lecture 2018 The American Chemical Society Cope Scholar Award 2018 The American Chemical Society Murray Goodman Memorial Prize 2020 The Franklin Institute & City Council of Philadelphia John C. Scott Award 2025 ACS Ronald Breslow Award for Achievement in Biomimetic Chemistry
Sources: en.wikipedia.org
No. Epithalamin is a peptide-containing extract of bovine pineal glands, while epitalon is a single synthetic tetrapeptide. The extract contains many peptides and other tissue components, so its composition varies between batches in ways that a synthesised sequence does not.
It is not recognised as an endogenous peptide hormone. The four-residue sequence can appear inside larger proteins and in digestive fragments of dietary protein, but no dedicated pathway producing it as a signalling molecule has been identified.
Several cell-culture reports describe increased telomerase activity after treatment, measured by enzyme assays or by transcript levels. Results differ between cell types and laboratories, and measured telomere lengthening has been reported in some studies but not in others, which leaves the physiological relevance open.
Mass spectrometry provides the identity check, because the observed mass is compared with the theoretical mass of the AEDG sequence. Chromatography separates and quantifies impurities but does not by itself prove which peptide is present. The two techniques are normally used together.