The short version of Reversed-phase HPLC fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-01-27. Anything still debated is marked as such rather than presented as settled.
Laboratory handling begins with dissolution of the lyophilized powder in water or a suitable aqueous buffer. The dry solid is the more stable form, so stock solutions are generally prepared only when required and kept cold afterwards. Repeated freezing and thawing of a solution is avoided because it encourages aggregation and gradual loss of the intact chain. Diluents and containers are selected to limit adsorption of a short peptide onto plastic surfaces and to reduce microbial growth in aqueous preparations.
Stability depends strongly on pH, temperature and the presence of oxygen and trace metals. Cleavage of the backbone proceeds faster under neutral to alkaline conditions, whereas acidic solutions tend to slow that reaction. The aspartate and glutamate side chains can undergo deamidation or imide formation over time, generating closely related impurities. Published stability data specific to epitalon are sparse, so the usable life of a given solution is best regarded as an open question that depends on buffer composition, concentration and storage temperature.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography with ultraviolet detection, frequently near 214 nanometers where the peptide bond absorbs. Mass spectrometry, most often with electrospray ionization, confirms the observed molecular mass and helps separate the intact peptide from truncated or modified forms. Amino acid analysis or tandem mass spectrometry can establish residue order. Purity is commonly quoted as an area percentage, yet such values are method-dependent, and comparisons between laboratories require matching column, gradient and detection wavelength.
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.
| Property | Value | Notes |
|---|---|---|
| Storage temperature, dry powder | -20 degrees Celsius or lower | Sealed, dark, low humidity |
| Storage temperature, solution | 2 to 8 degrees Celsius | Short-term use expected |
| Primary purity method | Reversed-phase HPLC | Ultraviolet detection near 214 nm |
| Identity confirmation | Electrospray mass spectrometry | Compared with calculated mass |
| Typical purity specification | Area percent of 95 or higher | Depends on column and gradient |
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.
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.
（TG:@pojiaai）Epitalon is a synthetic linear tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, abbreviated AEDG. It emerged from work on epithalamin, a peptide fraction prepared from bovine pineal tissue, and was designed as a short, chemically defined analogue of that extract. Early publications came mainly from Russian laboratories studying pineal peptides and aging-related endpoints. The compound appears in the literature under several spellings, including epithalon and epithalone, which complicates systematic searching. Its small size makes solid-phase assembly and routine analytical characterization straightforward.
At the end of 2019, the company employed 117,628 people, with over 54,000 in Germany. In 2019, BASF posted sales of €59.3 billion and income from operations before special items of about €4.5 billion. Between 1990 and 2005, the company invested €5.6 billion in Asia, specifically in sites near Nanjing, Shanghai and Zhanjiang in China and Mangalore in India. BASF is listed on the Frankfurt Stock Exchange, London Stock Exchange, and Zurich Stock Exchange. The company delisted its ADR from the New York Stock Exchange in September 2007. The company is a component of the Euro Stoxx 50 stock market index.
=== Skin === Deficiencies in vitamin A and retinoic acid have been linked to an increased susceptibility to skin infection and inflammation. Vitamin A appears to modulate the innate immune response and maintains homeostasis of epithelial tissues and mucosa through its metabolite, retinoic acid (RA). As part of the innate immune system, toll-like receptors in skin cells respond to pathogens and cell damage by inducing a pro-inflammatory immune response which includes increased RA production. The epithelium of the skin encounters bacteria, fungi and viruses. Keratinocytes of the epidermal layer of the skin produce and secrete antimicrobial peptides (AMPs). Production of AMPs resistin and cathelicidin, are promoted by RA. Another way that vitamin A helps maintain a healthy skin and hair follicle microbiome, especially on the face, is by reduction of sebum secretion, which is a nutrient source for bacteria. Retinol is used topically, in often unregulated cosmetic applications, claiming to mitigate the visible effects of ageing on the skin. Clinical and histological improvement is observed, but is not maintained after application is discontinued. When applied topically there is very little systemic absorption through the skin. Retinol has been the subject of clinical studies regarding its ability to reduce fine wrinkles and roughness on the face and neck. All-trans retinol has been used in over-the-counter cosmetic products since 1984.
=== Funerary terraces === Two funerary enclosures were discovered north of the voie d'Italie. The northernmost one was destroyed in 1973 to make way for the Centre Bourse. Each rectangular enclosure has an area of approximately 100 m2 (1,100 sq ft). They were in fact terraces intended to be seen from the voie d'Italie. The preserved enclosure is decorated with alternating metopes and triglyphs which rest on a plinth. In the center of this terrace a square-shaped plinth was discovered carved from large white limestone: it might have been the base of an altar or statue. The enclosures were built at the beginning of the 4th century BC. The excavations have revealed several cremations carried out in situ — nineteen in the northern enclosure and six next to the monument with triglyphs. The remains were recovered; they were found in lead, ceramic or bronze urns, which were then placed within stone boxes and arranged in a pit of funerary terraces. Some of these urns are exhibited at the Marseille History Museum. All the tombs date back to the 4th century BC, except for one cremation which might have occurred in the 3rd century BC. At the beginning of the 2nd century, the use of these funerary terraces was abandoned completely and the site covered up with earth.
Sources: en.wikipedia.org
=== Promotions === Pre-purchasing of the Windows version on Steam began on September 11, 2007. Those who pre-purchased via this method received a ten-percent discount and were able to play the Team Fortress 2 beta starting on September 17, 2007. The original PC version of The Orange Box came with Peggle Extreme, a ten-level playable demo of Peggle Deluxe, which contained levels with graphical themes of games contained in The Orange Box. However Peggle Extreme was later made free to download for anyone with a Steam account and is not included in the current PC version of the Orange Box on Steam. Half-Life 2: Lost Coast is also technically included with the PC version of The Orange Box, as it was offered as a free download to all owners of Half-Life 2. And as of 2024 is listed as a part of the Orange Box after Lost Coast and Half-Life 2 Episodes One, and Two were integrated into Half-Life 2 as a part of its 20th anniversary update. The same is true for Half-Life 2: Deathmatch, which is now included with Half-Life 2 following Half-Life 2's 20th anniversary update.
However, the degree of fractionation is not necessarily consistent between organisms, complicating the determination of paleosalinity with this method. There also appears to be a negative correlation between growth rate and fractionation in these coccolithophores. Further experiments on unicellular algae Eudorina unicocca and Volvox aureus show no effect of growth rate (controlled by nitrogen limitation) on fatty acid δD. However, sterols become more D-depleted as growth rate increases, in agreement with alkenone isotopic composition in coccolithophores. Overall, although there are some strong trends with lipid δD, the specific fractionations are compound-specific. As a result, any attempt to create a salinometer through δD measurements will necessarily be specific to a single compound type.
=== Change in anti-terrorist policy and "peripheral" nationalisms === The PP government developed an anti-terrorist policy based on an idea that no democratic government had defended until then: that only police measures could put an end to ETA. Thus, the only possible "dialogue" with ETA was the handing over of weapons. The government reaped a resounding first success with the release in early July 1997 of José Ortega Lara, a prison officer and PP militant who had been held hostage by ETA for 532 days. But a few days later, on July 10, an event took place that would open a new stage in the history of the "Basque conflict". That day ETA kidnapped Miguel Ángel Blanco, a young PP councilman from the Biscayan town of Ermua, which provoked the largest social mobilization against terrorism in living memory. But after the deadline given for the prisoners of the organization to be transferred to prisons in the Basque Country, ETA assassinated Miguel Ángel Blanco, which increased even more the rejection of ETA and its "political arm", Herri Batasuna. The press began to use the term "spirit of Ermua" to explain that immense anti-terrorist social mobilization. In March 1998, the lehendakari José Antonio Ardanza announced a "Pacification Plan" in which, based on the Ajuria Enea Pact of 1988, he proposed that after achieving the cessation of ETA's violence, a dialogue should be opened between all the Basque political forces, the result of which should be accepted by the central government and the rest of the institutions of the State.
When a specimen arrives in the microbiology laboratory, it is inoculated into an agar plate and placed in an incubator to encourage microbial growth. Because the appearance of microbial colonies changes as they grow, colonial morphology is examined at a specific time after the plate is inoculated. Usually, the plate is read at 18–24 hours post-inoculation, but times may differ for slower-growing organisms like fungi. The microbiologist examines the appearance of the colony, noting specific features such as size, colour, shape, consistency, and opacity. A hand lens or magnifying glass may be used to view colonies in greater detail. The opacity of a microbial colony can be described as transparent, translucent, or opaque. Staphylococci are usually opaque, while many Streptococcus species are translucent. The overall shape of the colony may be characterized as circular, irregular, or punctiform (like pinpoints). The vertical growth or elevation of the colony, another identifying characteristic, is assessed by tilting the agar plate to the side and is denoted as flat, raised, convex, pulvinate (very convex), umbilicate (having a depression in the centre) or umbonate (having a bump in the centre). The edge of the colony may be separately described using terms like smooth, rough, irregular and filamentous. Bacillus anthracis is notable for its filamentous appearance, which is sometimes described as resembling Medusa's head. Consistency is examined by physically manipulating the colony with a sterile instrument. It is described using terms like brittle, creamy, sticky and dry.
Sources: en.wikipedia.org
The dry powder is typically held at -20 degrees Celsius or lower, protected from light and moisture. Allowing a sealed vial to reach room temperature before opening reduces condensation on its contents. Conditions stated on a supplier certificate of analysis take precedence over general guidance.
Mass spectrometry supplies an observed molecular mass that is compared with the calculated value for the tetrapeptide. Reversed-phase chromatography then separates the main peak from related impurities. Neither technique alone establishes residue order, so sequence-level confirmation may call for tandem mass spectrometry or amino acid analysis.
No single published figure applies, because stability depends on pH, concentration, temperature and sterility. Cold storage slows hydrolysis without halting it, and microbial growth is a separate concern in non-sterile solutions. Most laboratories rely on their own analytical checks rather than a fixed expiry period.
It is a synthetic tetrapeptide built from alanine, glutamate, aspartate and glycine. The four residues are joined by standard peptide bonds, giving a linear chain rather than a branched structure.