reversed-phase HPLC comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2025-11-04. Where a claim depends on a specific study, the study is described rather than over-claimed.
Laboratory work has examined effects on telomerase activity in cultured cells, on melatonin rhythms in animals, and on markers of oxidative stress. Some experiments report measurable changes while others show none, and the reported findings rest largely on small studies. The absence of large independent trials means the generality of these results is unresolved rather than settled. Review articles occasionally apply the label geroprotector, a term that reflects a research hypothesis about ageing rather than an established clinical finding.
Epitalon is the common name for a synthetic tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, usually abbreviated AEDG. All four residues are proteinogenic amino acids, and the free peptide has a calculated mass near 390 grams per mole. Because the chain is short and carries no modifications, it is assembled readily by solid-phase synthesis and is distributed mainly as a freeze-dried solid for laboratory work. Catalogue listings use the spellings epitalon, epithalone, and simply AEDG, and the three refer to the same sequence.
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 | Computed for the free acid of Ala-Glu-Asp-Gly |
| Molecular mass | About 390.35 g/mol | Free peptide; salt forms shift the value |
| Appearance | White to off-white solid | Typical of short peptides after freeze-drying |
| Solubility class | Freely soluble in water | Aqueous buffers are also commonly used |
| Common synonyms | Epitalon, epithalone, AEDG | AEDG is the single-letter sequence |
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.
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.
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.
Discussions in the literature often conflate three distinct entities: the pineal extract epithalamin, the isolated tetrapeptide AEDG, and commercial preparations sold under similar names. Reviews citing older Russian-language studies sometimes omit detail on purity, route of administration and control groups, which makes cross-study comparison difficult. Researchers working with the compound generally note the need for independent replication, standardized enzyme assays, and clearer reporting of peptide identity. These caveats are relevant when weighing claims that appear in secondary sources rather than in primary reports.
Freeze-dried epitalon is normally kept at minus twenty degrees Celsius in a sealed, desiccated container, protected from light. Short excursions at ambient temperature during shipping are generally tolerated, but repeated warming and cooling cycles encourage moisture uptake, which shortens shelf life. Once dissolved, the peptide is far less stable than the solid: aqueous solutions are subject to hydrolysis and to deamidation at the aspartate and glutamate residues. Working solutions are therefore held refrigerated and used within days, and repeated freezing and thawing of the same vial is best avoided.
Identity and purity are checked by reversed-phase high-performance liquid chromatography, usually with ultraviolet detection near 214 nanometres, where the peptide bond absorbs. Mass spectrometry confirms the expected mass and reveals whether truncation products or adducts are present. Acid hydrolysis followed by amino acid analysis gives the residue ratio, which should approximate one alanine, one glutamate, one aspartate and one glycine. Counter-ions such as acetate or trifluoroacetate remain in the dried product and lower net peptide content, so a stated purity figure on a label does not by itself describe how much peptide a vial holds.
Regulatory treatment differs by country. No formulation of epitalon holds a marketing authorisation as a medicine in the United States or the European Union, where material sold for laboratory use is handled as a research chemical and is not intended for human consumption. In Russia, several short peptide preparations from the same institute's peptide series are registered medicinal products, and epitalon appears in that national context. Elsewhere it is frequently offered as a cosmetic ingredient, a category with lighter requirements. Advertising claims about longevity or disease prevention are restricted in most jurisdictions, which limits how sellers describe the compound.
=== Alprostadil === Alprostadil is used for two main purposes: the treatment of newborns with congenital heart defects and in treatment of erectile dysfunction. Some babies are born with heart defects which compromise blood flow to the body. In some defects, including tetralogy of Fallot, aortic valvular atresia, and Eisenmenger pulmonary hypertension, alprostadil is given intravenously by a nurse until surgery can be performed to repair the defect. The medication maintains a patent ductus arteriosus. The ductus arteriosus is a shortcut between the aorta and pulmonary artery, two large vessels branching off the heart. This shortcut allows the fetus to maintain blood flow before birth. However, it closes shortly after birth when the newborn can breathe oxygen. In babies with certain congenital defects, however, it's essential to keep the ductus arteriosus open to ensure at least some blood flow throughout the body. Side effects include decreased breathing or a lack of breathing at high doses. The medication can also cause hypotension, or low blood pressure. Alprostadil is also used for adults with erectile dysfunction. It is typically given when other medications are ineffective. The medication relaxes smooth muscle and allows the arteries in the corpus cavernosum of the penis to dilate. Blood then flows to the penis. This blood flow compresses the veins which drain blood from the penis, trapping the blood in the corpus cavernosum. This process leads to erection.
Most manipulations and assays are performed in the mixed-cell environments found in vivo, in "neuronal" cell cultures that contain significant numbers of glia, or in tumor-derived "neuronal" cell lines. When transfections or other manipulations have been targeted specifically at neurons, the endpoints measured are typically electrophysiology or other parameters far removed from gene transcription. Careful tests of NF-κB-dependent transcription in highly purified cultures of neurons generally show little to no NF-κB activity. Some of the reports of NF-κB in neurons appear to have been an artifact of antibody nonspecificity. Of course, artifacts of cell culture—e.g., removal of neurons from the influence of glia—could create spurious results as well. But this has been addressed in at least two co-culture approaches. Moerman et al. used a coculture format whereby neurons and glia could be separated after treatment for EMSA analysis, and they found that the NF-κB induced by glutamatergic stimuli was restricted to glia (and, intriguingly, only glia that had been in the presence of neurons for 48 hours). The same investigators explored the issue in another approach, utilizing neurons from an NF-κB reporter transgenic mouse cultured with wild-type glia; glutamatergic stimuli again failed to activate in neurons. Some of the DNA-binding activity noted under certain conditions (particularly that reported as constitutive) appears to result from Sp3 and Sp4 binding to a subset of κB enhancer sequences in neurons.
Human alpha-1-antitrypsin is another protein that has been produced from goats and is used in treating humans with this deficiency. Another medicinal area is in creating pigs with greater capacity for human organ transplants (xenotransplantation). Pigs have been genetically modified so that their organs can no longer carry retroviruses or have modifications to reduce the chance of rejection. Chimeric pigs could carry fully human organs. The first human transplant of a genetically modified pig heart occurred in 2023, and kidney in 2024. Livestock are modified with the intention of improving economically important traits such as growth-rate, quality of meat, milk composition, disease resistance and survival. Animals have been engineered to grow faster, be healthier and resist diseases. Modifications have also improved the wool production of sheep and udder health of cows. Goats have been genetically engineered to produce milk with strong spiderweb-like silk proteins in their milk. A GM pig called Enviropig was created with the capability of digesting plant phosphorus more efficiently than conventional pigs. They could reduce water pollution since they excrete 30 to 70% less phosphorus in manure. Dairy cows have been genetically engineered to produce milk that would be the same as human breast milk. This could potentially benefit mothers who cannot produce breast milk but want their children to have breast milk rather than formula. Researchers have also developed a genetically engineered cow that produces allergy-free milk.
CYP2D6 metabolizer phenotypes do not modify psilocin exposure in humans, suggesting that CYP2D6 is not critically involved in psilocin metabolism and is unlikely to result in interindividual differences in psilocin kinetics or effects. Psilocybin and psilocin might inhibit CYP3A4 and CYP2A6 to some extent, respectively.
Sources: en.wikipedia.org
calculates the abundance of carbon-13 relative to carbon-12 in all methane molecules. For the random distribution (i.e. probability distribution), the probability of choosing a carbon-13 atom over a carbon-12 atom is
=== New owner === On 23 February 2023, Giant's operator Dairy Farm announced that it was exiting the grocery retail market in Malaysia, citing increasing competition. Dairy Farm's grocery business in Malaysia was sold to Macrovalue Sdn Bhd led by Andrew Lim Tatt Keong, a local businessman and entrepreneur. Dairy Farm, however, would still remain the operator of the Cold Storage and Giant franchise in Singapore until 2025, where it will be sold to Macrovalue Pte Ltd in March 2025. Following the acquisition, Macrovalue announced that Giant Hypermarket in both Singapore and Malaysia will be rebranded as Giant Mall as the parent company attempts to attract more foot traffic and cut down losses.
=== Julia Braverman-Graham === Julia Braverman-Graham (Erika Christensen) is Sydney and Victor's mother, Joel's wife, and Zeek and Camille's fourth and youngest child and second daughter. She is a lawyer at a top corporate firm while her husband, Joel, supports her ambitions by serving as a stay-at-home dad to their daughter. Julia is sometimes competitive and it is difficult for her to let go and relax. Julia's go-getting personality and by-the-book approach is the opposite of her sister Sarah's, but they turn to one another for support. During the second season, Joel and Julia are celebrating their eight-year anniversary. After unsuccessfully trying to conceive a second child, Julia is told she has scarring in her uterus and that it will be extremely difficult for her to conceive again. Julia and Joel decide to adopt a young boy named Victor. During the fourth season, after missing Sydney's dance recital and Victor's first baseball game, as well as a discovery deadline for the law firm (a costly mistake for the firm), she quits her job at the firm. She then attempts to become a stay-at-home mom while Joel goes back to work. In season five, Julia begins to struggle with staying at home and feeling out of place. She begins a friendship with Ed, a dad at her children's school, and it begins to turn into an emotional affair. Eventually she sees the dangers and goes to break it off, but instead they kiss. Later in the season, after separating with Joel over her relationship with Ed, Julia has a one-night stand with Mr.
== Caveats == Several factors can affect the reliability of inter-country comparisons of resistance rates, due to differences in data quality and biased introduced during data collection and reporting. Several identified by EARS-Net are:
====== LAESI ====== In Laser ablation electrospray ionization (LAESI), a laser is used to ablate the surface of the sample and the emitted molecules are ionized in the gas phase by charged droplets from electrospray. Similar to DESI the ionization happens in ambient conditions. Anderton et al. used this ionization technique coupled to a Fourier transform mass spectrometer to analyze 200 single cells of Allium cepa (red onion) with high spatial resolution.
Sources: en.wikipedia.org
It is a four-amino-acid peptide with the sequence alanine-glutamate-aspartate-glycine. The chain is unmodified and contains only standard proteinogenic residues, which makes it straightforward to produce by solid-phase synthesis and to characterise by standard peptide methods.
Epitalon and epithalon both circulate, and the difference reflects transliteration of a name coined in Russian-language publications. Reference to the extract it derives from, epithalamin, explains the shared stem. Databases and suppliers are inconsistent, so a search for one spelling alone may miss relevant entries.
No. Epithalamin is a multi-component preparation obtained from pineal tissue, and its exact composition is not fully characterised. Epitalon is a single defined tetrapeptide described as a short synthetic counterpart of that extract, so the two are related in origin but not interchangeable in identity.
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.