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 2026-05-04. Where a claim depends on a specific study, the study is described rather than over-claimed.
Epitalon emerged from research conducted in Saint Petersburg by Vladimir Khavinson and colleagues, who studied short peptides as potential regulators of aging. The work built on epithalamin, a pineal gland extract reported to influence neuroendocrine function. Epitalon was designed as a synthetic counterpart with a defined sequence, allowing reproducible experiments that extracts could not support. Early publications described effects on melatonin rhythms and lifespan in animal models. These findings circulated mainly in Russian-language journals during the 1990s, which limited their visibility among English-speaking researchers.
The most widely cited claim is that epitalon activates telomerase and thereby extends telomere length. Supporting evidence comes largely from cultured human cells, where treatment was associated with increased telomerase activity and delayed replicative senescence. Telomerase activation is a biologically consequential effect, since the enzyme is largely silenced in most somatic cells. However, the route by which a short peptide would reach and act on the enzyme's regulatory machinery has not been established. Independent replication in human trials is scarce, so the link between cell-culture observations and whole-body aging remains an open question.
Documentation accompanying research peptides usually includes a certificate of analysis listing the batch number, purity figure, and test methods applied. Buyers comparing suppliers should check whether the reported purity refers to chromatographic area or to a mass-balance calculation, because the two are not equivalent. Counter-ion content, residual solvents, and water content are sometimes omitted from such certificates even though they affect the actual peptide mass present. Independent verification through a second laboratory is the most direct way to confirm that a supplied material matches its label.
Purity assessment of peptide reagents normally relies on reversed-phase high-performance liquid chromatography. A gradient of acetonitrile in water with trifluoroacetic acid, paired with a C18 stationary phase, separates the target tetrapeptide from truncated sequences and deletion analogues. Detection at 214 nanometres exploits absorbance of the peptide backbone, since the molecule contains no aromatic residue. Results are expressed as a percentage of total peak area. Values above ninety-five percent are typical for research-grade material, although reporting conventions vary between suppliers.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Ala-Glu-Asp-Gly | Single-letter form AEDG |
| Compound class | Synthetic tetrapeptide | Not a natural free peptide |
| Research origin | Russian gerontology institutes | Developed during the 1990s |
| Main research claim | Telomerase activation | Evidence mainly from cultured cells |
| Regulatory status | Not an approved drug | Handled as a research material |
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.
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.
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.
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.
Injury in humans has been studied extensively for its importance in medicine. Much of medical practice, including emergency medicine and pain management, is dedicated to treating injuries. The World Health Organization has developed a classification of injuries in humans by categories, including mechanism, objects/substances producing injury, place of occurrence, activity when injured, and the role of human intent. In addition to physical harm, injuries can cause psychological harm, including post-traumatic stress disorder, or depression (mood).
As the drug has increasingly been seen as a health issue instead of criminal behavior, cannabis has also been legalized or decriminalized in: Czech Republic, Colombia, Ecuador, Portugal, South Africa and Canada. Medical marijuana was legalized in Mexico in mid-2017 and legalized for recreational use in June 2021. Germany legalized cannabis for recreational use in April 2024.
==== Temporary ==== High-velocity objects are usually projectiles such as bullets from high-powered rifles, such as assault rifles or sniper rifles. Bullets classed as medium-velocity projectiles include those from handguns, shotguns, and submachine guns. In addition to causing damage to the tissues they contact, medium- and high-velocity projectiles cause a secondary cavitation injury: as the object enters the body, it creates a pressure wave which forces tissue out of the way, creating a cavity which can be much larger than the object itself; this is called "temporary cavitation". The temporary cavity is the radial stretching of tissue around the bullet's wound track, which momentarily leaves an empty space caused by high pressures surrounding the projectile that accelerate material away from its path. The characteristics of the tissue injured also help determine the severity of the injury; for example, the denser the tissue, the greater the amount of energy transmitted to it. Skin, muscles, and intestines absorb energy and so are resistant to the development of temporary cavitation, while organs such as the liver, spleen, kidney, and brain, which have relatively low tensile strength, are likely to split or shatter because of temporary cavitation. Flexible elastic soft tissues, such as muscle, intestine, skin, and blood vessels, are good energy absorbers and are resistant to tissue stretch. If enough energy is transferred, the liver may disintegrate.
=== 1970s === Israel responded to the Arab Yom Kippur War attack on 6 October 1973 by assembling 13 nuclear weapons in a tunnel under the Negev desert when Syrian tanks were sweeping in across the Golan Heights. On 8 October 1973, Israeli Prime Minister Golda Meir authorized Defense Minister Moshe Dayan to activate the 13 Israeli nuclear warheads and distribute them to Israeli air force units, with the intent that they be used if Israel began to be overrun. On 24 October 1973, as US President Richard Nixon was preoccupied with the Watergate scandal, Henry Kissinger ordered a DEFCON-3 alert preparing American B-52 nuclear bombers for war. Intelligence reports indicated that the USSR was preparing to defend Egypt in its Yom Kippur War with Israel. It had become apparent that if Israel had dropped nuclear weapons on Egypt or Syria, as it prepared to do, then the USSR would have retaliated against Israel, with the US then committed to providing Israeli assistance, possibly escalating to a general nuclear war. By the late 1970s, people in both the United States and the Soviet Union, along with the rest of the world, had been living with the concept of mutual assured destruction (MAD) for about a decade, and it became deeply ingrained into the psyche and popular culture of those countries. On May 18, 1974, India conducted its first nuclear test in the Pokhran test range. The name of the operation was Smiling Buddha, and India termed the test as a "peaceful nuclear explosion." The Soviet Duga early warning over-the-horizon radar system was made operational in 1976.
Sources: en.wikipedia.org
Initial letters are used where there is no ambiguity: C cysteine, H histidine, I isoleucine, M methionine, S serine, V valine. No other amino acids in this set begin with each of those letters. Where arbitrary assignment is needed, the structurally simpler amino acids are given precedence: A alanine, G glycine, L leucine, P proline, T threonine. For example, alanine is simpler than arginine or asparagine, the other amino acids starting with "a". F PHenylalanine and R aRginine are assigned by being phonetically suggestive, W tryptophan is assigned based on the double ring being visually suggestive to the bulky letter W, K lysine and Y tyrosine are assigned as alphabetically nearest to their initials L and T (note that U was avoided for its similarity with V, while X was reserved for undetermined or atypical amino acids); for tyrosine the mnemonic tYrosine was also proposed, D aspartate was assigned arbitrarily, with the proposed mnemonic asparDic acid; E glutamate was assigned in alphabetical sequence being larger by merely one methylene –CH2– group, N asparagine was assigned arbitrarily, with the proposed mnemonic asparagiNe; Q glutamine was assigned in alphabetical sequence of those still available (note again that O was avoided due to similarity with D), with the proposed mnemonic Qlutamine.
When an 235U atom captures a neutron, it is converted to an excited state of 236U. About 85.5% of the excited 236U nuclei undergo fission, but the remainder decay to the ground state of 236U by emitting gamma radiation. Further neutron capture forms 237U which has a half-life of 7 days and quickly decays to 237Np through beta decay. During beta decay, the excited 237U emits an electron, while the atomic weak interaction converts a neutron to a proton, thus creating 237Np.
== In the heart == In the heart, A1 receptors play roles in electrical pacing (chronotropy and dromotropy), fluid balance, local sympathetic regulation, and metabolism. When bound by adenosine, A1 receptors inhibit impulses generated in supraventricular tissue (SA node, AV node) and the Bundle of His/Purkinje system, leading to negative chronotropy (slowing of the heart rate). Specifically, A1 receptor activation leads to inactivation of the inwardly rectifying K+ current and inhibition of the inward Ca2+ current (ICa) and the 'funny' hyperpolarization-activated current (If). Adenosine agonism of A1ARs also inhibits release of norepinephrine from cardiac nerves. Norepinephrine is a positive chronotrope, inotrope, and dromotrope, through its agonism of β adrenergic receptors on pacemaker cells and ventricular myocytes. Collectively, these mechanisms lead to an myocardial depressant effect by decreasing the conduction of electrical impulses and suppressing pacemaker cells function, resulting in a decrease in heart rate. This makes adenosine a useful medication for treating and diagnosing tachyarrhythmias, or excessively fast heart rates. This effect on the A1 receptor also explains why there is a brief moment of cardiac standstill when adenosine is administered as a rapid IV push during cardiac resuscitation. The rapid infusion causes a momentary myocardial stunning effect. In normal physiological states, this serves as protective mechanisms.
Sources: en.wikipedia.org
Vladimir Khavinson and colleagues at research institutes in Saint Petersburg developed and studied the peptide. Their program examined short peptides as regulators of aging and neuroendocrine function. Epitalon was one of several compounds produced by that group.
That question is not settled. Cell culture studies have reported increased telomerase activity after treatment, but comparable evidence from controlled human trials is lacking. Any claim about telomere lengthening in people should be treated as unproven.
It has not completed the large, controlled trials required for drug approval in major jurisdictions. Most human reports involve small samples and limited follow-up. As a result, it is sold as a research chemical rather than a licensed pharmaceutical product.
Reversed-phase high-performance liquid chromatography with ultraviolet detection at 214 nanometres is the usual approach. Peak area percentage provides a purity figure relative to other components in the sample. Mass spectrometry is then applied to confirm identity.