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 2026-05-20 and is reviewed periodically as new material appears.
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.
Interest in epitalon is usually discussed within the broader field of short peptide bioregulators, a category that includes other synthetic di-, tri-, and tetrapeptides studied by the same research group. These compounds share a common rationale: that small fragments of tissue-derived proteins can retain biological activity and can be produced reproducibly. The category as a whole remains outside mainstream pharmacological consensus, and epitalon specifically has a limited presence in independent, non-Russian research literature, which shapes how its evidence base is described.
Epitalon is a synthetic tetrapeptide with the amino acid sequence alanine-glutamate-aspartate-glycine, abbreviated Ala-Glu-Asp-Gly or AEDG. It was developed by the Russian researcher Vladimir Khavinson and colleagues during work on peptide bioregulators derived from the pineal gland. The compound is short enough to be produced by standard solid-phase peptide synthesis and is typically handled as a lyophilized white powder. Its small size distinguishes it from larger pineal peptides such as epithalamin, a complex extract from which the tetrapeptide was conceptually derived.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised and often hygroscopic |
| Solubility class | Freely soluble in water | Poor solubility in non-polar solvents |
| Typical storage temperature | -20 degrees Celsius or colder | Sealed, desiccated, protected from light |
| Typical analytical method | Reversed-phase HPLC with mass spectrometry | Establishes purity and confirms mass |
| Common salt form | Trifluoroacetate or acetate | Counterion reported alongside purity values |
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.
Epitalon is a synthetic four-amino-acid peptide with the sequence alanine-glutamate-aspartate-glycine, commonly abbreviated AEDG. Its molecular formula is C14H22N4O9, and its calculated molar mass is approximately 390.35 grams per mole. The compound is a short fragment related to a peptide fraction isolated from bovine pineal gland extracts, and it is normally supplied as a lyophilised powder intended for laboratory research. It is not a registered pharmaceutical product in most countries.
The peptide emerged from research carried out in Saint Petersburg from the late 1980s onward, where investigators searched for shorter active fragments of a pineal preparation known as epithalamin. The name epitalon was chosen to reflect that parent extract. Early reports described effects on neuroendocrine markers and on the lifespan of laboratory animals. Much of that work appeared in Russian-language journals, with English translations following later, which affects how readily the original protocols can be assessed by outside groups.
Published studies on epitalon are dominated by a small number of research groups, and independent replication in other laboratories remains limited. Proposed mechanisms include activation of telomerase and modulation of melatonin rhythms, but the evidence for either rests mainly on cell cultures and animal models. Whether the peptide produces comparable effects in humans is an open question, and the absence of large controlled trials means the literature is best read as exploratory rather than settled.
natural vs synthetic, e.g. glycine vs caprolactam, respectively polar vs nonpolar, e.g. vinyl acetate vs ethylene, respectively cyclic vs linear, e.g. ethylene oxide vs ethylene glycol, respectively By type of polymer they form:
Because the molecular weight of endotoxins is usually over 10 kD, ultrafiltration can sometimes be used to perform as a size based separation. Due to the high variability of endotoxin size, it can be difficult to select the correct membrane, hence this method is best used only when all endotoxins present are larger than 300,000 Da. Commercially available ultra filters have been shown to remove pyrogens to a level below 0.001 EU/ml.
=== Processed products === More and more, potatoes are consumed and cooked through industrially processed products, mainly frozen products, most often precooked, or dehydrated (e.g., potato flakes, granules, flour). The share of processed products exceeds that of table potatoes in some Western countries (United States, Canada, Northern Europe). In Germany, for example, in 2003–2004, processed potatoes accounted for 34.3 kg per capita per year, compared to 32.5 kg for table potatoes. In the United States, the use of fresh potatoes represented, in 2007, only one third of the total consumption. Most of the time, these are "ready to cook" products, which have the advantage of facilitating the preparation of meals, eliminating the need for tedious peeling, and which can be stored more easily and longer than fresh tubers. The most commonly used are dehydrated flaked mashed potatoes, or instant mashed potatoes, and pre-cooked frozen French fries. The latter are more commonly consumed in the catering industry. The simplest are peeled and pre-cooked vacuum-packed potatoes, which belong to the category of fresh products, known as fifth range. Canned potatoes (tins or jars) are also available on the market, sometimes mixed with carrots or peas. Potato chips are a special case, since this product is consumed directly, without any culinary preparation, and most often outside the meal.
Sources: en.wikipedia.org
=== Water === The biological half-life of water in a human is about 7 to 14 days. It can be altered by behavior. Drinking large amounts of alcohol will reduce the biological half-life of water in the body. This has been used to decontaminate patients who are internally contaminated with tritiated water. The basis of this decontamination method is to increase the rate at which the water in the body is replaced with new water.
=== Apodization in astronomy === Apodization is used in telescope optics to improve the dynamic range of the image. For example, stars with low intensity in the close vicinity of very bright stars can be made visible using this technique, and even images of planets can be obtained when otherwise obscured by the bright atmosphere of the star they orbit. Generally, apodization reduces the resolution of an optical image; however, because it reduces diffraction edge effects, it can actually enhance certain small details. In fact, the notion of resolution, as it is commonly defined with the Rayleigh criterion, is in this case partially irrelevant. One has to understand that the image formed in the focal plane of a lens (or a mirror) is modeled through the Fresnel diffraction formalism. The classical diffraction pattern, the Airy disk, is connected to a circular pupil, without any obstruction, and with a uniform transmission. Any change in the shape of the pupil (for example a square instead of a circle), or its transmission, results in an alteration to the associated diffraction pattern.
==== Indications ==== Nabilone, marketed under the brand name Cesamet®, is a synthetic form of tetrahydrocannabinol (THC). It is used to treat chemotherapy-induced nausea and vomiting in cancer patients who fail to have sufficient response to conventional antiemetic treatments. It is also used to treat anorexia and weight loss in AIDS patients.
A Cochrane Review on treatments for acute CRAO included one randomized clinical trial involving pentoxifylline, which showed that pentoxifylline use (three 600 mg tablets daily) was associated with improved retinal perfusion, but it was unclear if significant improvements in visual acuity were also observed. Similar findings have been shown using Doppler OCT imaging in patients with NAION, though a study in India reported visual improvement compared to placebo in patients with optic neuropathy. Of note, TNF may be important in the immune response to certain nematode parasitic infections, and so pentoxifylline should be used with caution for those living in areas of parasite infestation; however, it is probably safe to use in otherwise healthy individuals living in urban, temperate environments. Overall, routine use of pentoxifylline in ischemic optic neuropathies was not supported given limited evidence, but the absence of major adverse effects and the absence of other proven therapies suggest a possible therapeutic role for pentoxifylline.
Sources: en.wikipedia.org
Chymopapain is one of the substracts used in chemonucleolysis (a type of percutaneous discectomy). This method was a new proposal to treat primary lumbar intervertebral disc disease using a nonsurgical method. As a matter of fact, the treatment consists on an injection of proteolytic enzymes to dissolve the herniated nucleus pulposus of the intervertebral discs. Purified chymopapain is the main component of the injection, composed basically of 20 mg in five millilitres. It is provided in vials containing 10.000 units of the lyophilized agent with 0.37 mg of disodium edetate, 3.5 mg of cysteine hydrochloride monohydrate and 1.0 mg of bisulfide. All of them work as stabilisers and activators. Sodium hydroxide is in charge of adjusting the PH of the solution. Then, the injection is rehydrated with 5 milliliters of sterile water. A surgeon injects the solution directly into the herniated disc on the spine to dissolve part of it and ease the pain. This process is under fluoroscopic control. Chymopapain is responsible for catalysis, both in vivo and in vitro, a rapid reduction in the viscosity and, as a consequence, the weight of the nucleus pulposus. In fact, it is a depolymerization of the chondromucoprotein and a decrease in the ability of a disk to imbibe fluid. The dose for a single intervertebral disc is 2 to 4 nanokatals, with a maximum dose per patient of 8 nanokatals. Chymopapain injections are normally given under local, rather than general, anaesthesia. This enzyme has been studied by universities departments around the world.
== Occurrence == Like other carotenoids, xanthophylls are found in highest quantity in the leaves of most green plants, where they act to modulate light energy and perhaps serve as a non-photochemical quenching agent to deal with triplet chlorophyll (an excited form of chlorophyll), which is overproduced at high light levels in photosynthesis. The xanthophylls found in the bodies of animals including humans, and in dietary animal products, are ultimately derived from plant sources in the diet. For example, the yellow color of chicken egg yolks, fat, and skin comes from ingested xanthophylls—primarily lutein, which is added to chicken feed for this purpose. The yellow color of the macula lutea (literally, yellow spot) in the retina of the human eye results from the presence of lutein and zeaxanthin. Again, both these specific xanthophylls require a source in the human diet to be present in the human eye. They absorb blue and ultraviolet light, thereby protecting the retina from the latter; but xanthophylls do not function in the mechanism of sight itself as they cannot be converted to retinal (also called retinaldehyde or vitamin A aldehyde). Their physical arrangement in the macula lutea is believed to be the cause of Haidinger's brush, an entoptic phenomenon that enables perception of polarized light.
== Applications == Freeze-drying (lyophilization) cycle development and optimization for pharmaceuticals. Flow diagnostics in hypersonic/re-entry speed research facilities and scramjet combustors. Oxygen tunable diode laser spectrometers play an important role in safety applications in a wide range of industrial processes, for this reason, TDLS are often an integral part of modern chemical plants. The fast response time compared to other technologies for measuring gas composition, and the immunity to many background gasses and environmental conditions makes TDL technology a commonly selected technology for monitoring of combustible gasses in process environments. This technology is employed on flares, in vessel headspace and in other locations where explosive atmospheres must be prevented from forming. According to a 2018 research study, TDL technology is the 4th most commonly selected technology for gas analysis in Chemical Processing.
Sources: en.wikipedia.org
Sealed lyophilised powder is normally kept at minus twenty degrees Celsius or below, away from light and moisture. Vials are allowed to reach room temperature before opening to limit condensation. Repeated warming and cooling of the same vial is discouraged.
Reversed-phase HPLC establishes purity and separation from related peptides, and mass spectrometry confirms the molecular mass. Amino acid analysis can verify residue composition. No single method proves identity on its own, so the results are read together.
Yes. Residual trifluoroacetate or acetate from purification adds mass and can shift the value obtained by certain assays. Purity figures are therefore meaningful only when the counterion form is stated. Reporting both peptide content and salt form gives a clearer picture.
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.