A practical reference on reversed-phase HPLC: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-01-01 and is reviewed periodically as new material appears.
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.
The compound is generally described as a synthetic analogue of a fragment isolated from a pineal gland extract. Researchers associated with the Saint Petersburg Institute of Bioregulation and Gerontology introduced it during the 1980s and 1990s while studying short peptides from animal tissue. The original extract, called epithalamin, is a heterogeneous mixture, whereas epitalon is a single defined sequence. That distinction matters because findings reported for the extract are not automatically findings about the pure tetrapeptide, and claims about broader biological effects remain a separate question from the chemical identity described here.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C14H22N4O9 | Derived from the four constituent residues |
| Molecular mass | About 390.35 Da | Monoisotopic value, confirmed by mass spectrometry |
| Residue sequence | Ala-Glu-Asp-Gly | Read from the N-terminus to the C-terminus |
| Common synonyms | Epithalon; AEDG | Both forms appear in reference catalogues |
| Net charge near neutral pH | Negative | Two acidic side chains give a low isoelectric point |
The compound is generally presented as a synthetic fragment of epithalamin, a pineal gland extract investigated in the former Soviet Union from the 1970s onward. Vladimir Khavinson and colleagues in Saint Petersburg developed short peptides modelled on such extracts, and epitalon became the most widely cited of those sequences. Most primary reports appeared in Russian-language journals or in proceedings with limited international circulation. Independent replication in laboratories outside that network remains sparse, and much repeated secondary material traces back to a small number of originating groups.
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.
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.
=== Hydrodynamic chromatography === Hydrodynamic chromatography (HDC) is derived from the observed phenomenon that large droplets move faster than small ones. In a column, this happens because the center of mass of larger droplets is prevented from being as close to the sides of the column as smaller droplets because of their larger overall size. Larger droplets will elute first from the middle of the column while smaller droplets stick to the sides of the column and elute last. This form of chromatography is useful for separating analytes by molar mass (or molecular mass), size, shape, and structure when used in conjunction with light scattering detectors, viscometers, and refractometers. The two main types of HDC are open tube and packed column. Open tube offers rapid separation times for small particles, whereas packed column HDC can increase resolution and is better suited for particles with an average molecular mass larger than
AAS that have a high potential for aromatization like testosterone and particularly methyltestosterone show a high risk of gynecomastia at sufficiently high dosages, while AAS that have a reduced potential for aromatization like nandrolone show a much lower risk (though still potentially significant at high dosages). In contrast, AAS that are 4,5α-reduced, and some other AAS (e.g., 11β-methylated 19-nortestosterone derivatives), have no risk of gynecomastia. In addition to gynecomastia, AAS with high estrogenicity have increased antigonadotropic activity, which results in increased potency in suppression of the hypothalamic–pituitary–gonadal axis and gonadal testosterone production.
=== Spectrum of activity and susceptibility data === Bacitracin is a narrow-spectrum antibiotic. It targets Gram-positive bacteria, especially those that cause skin infections. The following represents susceptibility data for a few medically significant microorganisms.
== Scope and access == The CompTox Chemicals Dashboard database contains high quality chemical structures and information that have been extensively curated and quality checked, which can be used as a resource for analytical scientists involved in structure identification.
==== Mixed oxidant ==== A simple brine {salt + water} solution in an electrolytic reaction produces a powerful mixed oxidant disinfectant (mostly chlorine in the form of hypochlorous acid (HOCl) and some peroxide, ozone, chlorine dioxide).
Sources: en.wikipedia.org
== Tissue damage == The tissue damage depends primarily on the absorbed energy and the tissue sensitivity; it is a function of the microwave power density (which depends on the distance from the source and its power output), frequency, absorption rate in the given tissue, and the tissue sensitivity. Tissues with high water (respectively electrolyte) content show higher microwave absorption. The degree of the tissue damage depends on both the achieved temperature and the length of exposure. For short times, higher temperatures can be tolerated. The damage can be spread over a large area, when the source is a relatively distant energy radiator, or a very small (though possibly deep) area, when the body comes to a direct contact with the source (e.g. a wire or a connector pin). The epidermis has high electrical resistance for lower frequencies; at higher frequencies, the energy penetrates through by capacitive coupling. Damage to epidermis has low extent unless the epidermis is very moist. The characteristic depth for lower-frequency microwave injury is about 1 cm. The heating rate of adipose tissue is much lower than that of muscle tissue. Frequencies in millimeter wave range are absorbed in the topmost layer of skin, which is rich in thermal sensors. At lower frequencies, between 1–10 GHz, most of the energy is however absorbed in deeper layers; the threshold for cellular injury there lies at 42 °C while the pain threshold is at 45 °C, so a subjective perception may not be a reliable indicator of a harmful level of exposure at those frequencies.
== Demography and epidemiology == Demography and quantitative epidemiology are statistical fields that deal with counts or proportions of people, or rates of change in these. Counts and proportions are technically dimensionless, and so have no units of measurement, although identifiers such as "people", "births", "infections" and the like are used for clarity. Rates of change are counts per unit of time and strictly have inverse time dimensions (per unit of time). In demography and epidemiology expressions such as "deaths per year" are used to clarify what is being measured. Prevalence, a common measure in epidemiology, is strictly a type of denominator data, a dimensionless ratio or proportion. Prevalence may be expressed as a fraction, a percentage or as the number of cases per 1,000, 10,000, or 100,000 in the population of interest.
If the target DNA contains an allele complementary to the probe's 3’ base, the target DNA will completely hybridize to the probe, allowing DNA polymerase to extend from the 3’ end of the probe. This is detected by the incorporation of the fluorescently labeled dNTPs onto the end of the probe. If the target DNA does not contain an allele complementary to the probe's 3’ base, the target DNA will produce a mismatch at the 3’ end of the probe and DNA polymerase will not be able to extend from the 3' end of the probe. The benefit of the second approach is that several labeled dNTPs may get incorporated into the growing strand, allowing for increased signal. However, DNA polymerase in some rare cases, can extend from mismatched 3’ probes giving a false positive result. A different approach is used by Sequenom's iPLEX SNP genotyping method, which uses a MassARRAY mass spectrometer. Extension probes are designed in such a way that 40 different SNP assays can be amplified and analyzed in a PCR cocktail. The extension reaction uses ddNTPs as above, but the detection of the SNP allele is dependent on the actual mass of the extension product and not on a fluorescent molecule. This method is for low to medium high throughput, and is not intended for whole genome scanning. The flexibility and specificity of primer extension make it amenable to high throughput analysis. Primer extension probes can be arrayed on slides allowing for many SNPs to be genotyped at once.
In February 2023, Moore announced a $600 million, five-year partnership with the Baltimore Orioles to develop properties around Camden Yards. In September 2023, he and Orioles CEO John P. Angelos announced a memorandum of understanding that would extend the team's lease by 30 years, open development rights inside the park to private developers, and give the Orioles control over stadium operations and maintenance. The stadium lease was finalized in December 2023, but an agreement on the team's ground lease and redevelopment plan was postponed until 2027 following concerns from Senate President Bill Ferguson. Orioles CEO David Rubenstein later wrote in his book, Inside the Owner’s Box, that he wanted to focus on the roster and ongoing ballpark upgrades before pursuing real estate development around Camden Yards. In September 2026, Rubenstein engaged real estate firm Seregh to begin a "multiyear effort to try to redevelop the immediate area around Camden Yards". Moore supported keeping the Washington Commanders, who are contractually obligated to play at Northwest Stadium until September 2027, in Maryland. He initially said that he would not support spending state funds to keep the Commanders in Maryland, but later reiterated that he supported spending some taxpayer money on a new Commanders football stadium "if we know there's going to be a significant societal return on the investment". In November 2024, Moore opposed a federal bill to give Washington, D.C. greater control of the Robert F.
Sources: en.wikipedia.org
It is a four-amino-acid peptide built from alanine, glutamate, aspartate and glycine in that order. Its formula is C14H22N4O9, and it is made by chemical synthesis rather than extracted from tissue. The synthetic peptide is a single defined molecule, unlike the pineal extracts it is often compared with.
No. The two spellings refer to the same tetrapeptide, and the difference reflects transliteration from Russian. Laboratories and catalogues use both forms interchangeably. The material is also indexed as AEDG, taken from the one-letter codes of its residues.
Epithalamin is a mixed preparation derived from animal pineal tissue and contains many peptides. Epitalon is one synthetic sequence chosen for study from that broader mixture. Statements about one do not transfer directly to the other.
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.