This is a working overview of reversed-phase HPLC, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-10-24 and is reviewed periodically as new material appears.
Stability of the tetrapeptide follows ordinary peptide chemistry rather than any unusual structural feature. The aspartate-glycine pair is prone to aspartimide formation under mildly basic or neutral conditions, and deamidation can follow, altering both mass and chromatographic retention. Dry lyophilised powder kept at or below minus twenty degrees Celsius is the usual handling recommendation, with repeated freeze-thaw cycles avoided. Once dissolved in neutral aqueous buffer, degradation proceeds over days to weeks depending on pH and temperature, while acidic conditions generally slow the aspartimide route. A formal stability-indicating study has not been published in the indexed literature.
Because epitalon has no pharmacopoeial monograph, quality assessment depends on supplier documentation and independent testing. Certificates of analysis typically report a purity figure from a single chromatographic run, a measured mass and sometimes an appearance description, but methods and acceptance criteria are not harmonised across vendors. Third-party laboratories can repeat identity and purity measurements, and mismatches between labelled and measured peptide content have been described for research peptides generally. What constitutes adequate identity confirmation for a molecule of this size stays an open question, since mass agreement alone does not separate closely related sequences.
Identity testing for epitalon relies on reversed-phase high-performance liquid chromatography for purity and mass spectrometry for mass confirmation. Because the sequence contains no tryptophan or tyrosine, ultraviolet detection at 280 nanometres is insensitive, so chromatographic methods usually monitor absorbance near 214 nanometres, where the peptide backbone absorbs. Electrospray ionisation or matrix-assisted laser desorption/ionisation then checks the intact mass against the expected value near 390 daltons. Peptide mapping or amino acid analysis after acid hydrolysis can supplement these measurements, although such confirmatory work is seldom reported on commercial certificates of analysis.
The published literature is dominated by a small number of research groups, much of it in Russian-language journals, and independent replication outside those groups is limited. Studies are typically small, use cultured cells or rodent models, and report endpoints that differ between papers, which makes comparison difficult. Large randomised human trials have not appeared in the indexed literature. Questions about absorption, distribution and clearance are therefore still treated as open in reviews that mention the compound.
Epitalon is a synthetic tetrapeptide with the sequence alanine–glutamate–aspartate–glycine, commonly abbreviated AEDG. Its design traces to epithalamin, a peptide fraction prepared from bovine pineal gland extracts that researchers in Saint Petersburg began investigating in the 1970s. The compound has a molecular formula of C14H22N4O9 and a nominal molecular mass near 390 daltons. It holds no approved drug status in the United States or the European Union, and material sold under this name is generally offered as a research chemical rather than a finished pharmaceutical product.
Proposed mechanisms centre on cell-culture observations rather than a defined receptor interaction. Several reports describe increased expression of the telomerase catalytic subunit after exposure of cultured human cells, and the authors attributed the effect to short peptide fragments entering the nucleus and influencing gene transcription. No receptor for the tetrapeptide has been identified, and the free peptide is expected to be degraded rapidly by plasma peptidases. Whether any measurable fraction reaches intact tissues after administration remains an unresolved question rather than an established finding.
| Property | Value | Notes |
|---|---|---|
| Analytical method | Reversed-phase HPLC | Purity determination, typically 214 nm |
| Mass confirmation | ESI or MALDI mass spectrometry | Compared with mass near 390 Da |
| Common synonyms | Epitalon, epithalon, AEDG | Naming differs between suppliers |
| Storage temperature | −20 °C or lower | Lyophilised powder, kept desiccated |
| Solution stability | Limited in neutral aqueous buffer | Aspartimide and hydrolysis pathways |
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.
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.
In its supplied form epitalon is a white to off-white powder, usually lyophilized and often hygroscopic. It dissolves readily in water and in aqueous buffers, and it is commonly handled as the acetate or trifluoroacetate salt to improve stability during purification and drying. The amide backbone is labile in aqueous media, so solutions are less durable than the dry solid. Handling notes in the chemical literature therefore emphasize keeping the powder dry, cool and shielded from light until it is dissolved.
Epitalon is a synthetic tetrapeptide whose sequence is alanine-glutamate-aspartate-glycine, written in single-letter code as AEDG. The four residues are joined by three peptide bonds, giving a linear backbone with no branching and no disulfide bridges. Its calculated molecular mass for the free form is approximately 390.3 daltons, a figure that rises when the compound is supplied as an acetate or trifluoroacetate salt. Because the chain is short, the molecule is defined entirely by its residue order rather than by any folded three-dimensional structure.
The compound is described in the literature as a derivative of epithalamin, a preparation obtained from bovine pineal tissue. Work on this peptide family was carried out mainly by a research group in Saint Petersburg beginning in the 1980s, and the substance was later registered for clinical use in Russia under the name Epitalon. Outside that region it is generally treated as a research chemical rather than an approved medicine. Statements about its biological activity rest on a relatively small number of studies, and independent replication remains limited.
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.
Asparagopsis, a seaweed native to Australia, contains bioactives that interrupt the microbes in a cow's stomach that form methane. It is the most efficient natural methane supplement available for livestock – capable of reducing methane emissions by more than 80 per cent in controlled conditions. Asparagopsis can be included in feed and supplements as a stabilised freeze-dried powder, or in an edible oil. FutureFeed research has included the supplement in feedlot and dairy total mixed rations (TMR) and dairy cows supplemented twice daily at milking. A decade of science has shown this to be a safe and effective feed ingredient for livestock. Research into livestock methane production has shown that up to 12% of energy that fodder produces during digestion is lost as methane gas emissions, primarily from belching. It is a common misconception that the majority of methane emissions from livestock is through flatulent gas. Flatulent gas contributes to less than 10% of methane emissions as opposed to belching which contributes up to 95%. This is caused by bacteria living within the first stomach, known as the rumen, which serves as a 'fermentation tank' to effectively break down nutrients during digestion. Methane production represents an inefficiency of energy conversion that would otherwise contribute to the productive metabolism of livestock, such as milk, muscle or wool production. Productivity improvements are directly related to the quality of feed that is ingested.
==== MiniMed 670G ==== In September 2016, the FDA approved the Medtronic MiniMed 670G, which was the first approved hybrid closed loop system. The device automatically adjusts a patient's basal insulin delivery. It is made up of a continuous glucose monitor, an insulin pump, and a glucose meter for calibration. It automatically functions to modify the level of insulin delivery based on the detection of blood glucose levels by continuous monitor. It does this by sending the blood glucose data through an algorithm that analyzes and makes the subsequent adjustments. The system has two modes. Manual mode lets the user choose the rate at which basal insulin is delivered. Auto mode regulates basal insulin levels from the CGM readings every five minutes.
=== Preclinical === AC-203 – unspecified – alopecia areata – cell death modulator ADA-308 – topical – alopecia – androgen receptor antagonist BMD-1141 (BMD-1341) – subcutaneous injection – alopecia – parathyroid hormone receptor agonist Crebankitug (ZB-168) – parenteral – alopecia areata – interleukin 7 receptor α subunit inhibitor, thymic stromal lymphopoietin inhibitor CS-12192 – oral – alopecia areata – Janus kinase 1 inhibitor, Janus kinase 3 inhibitor, TBK1 protein inhibitor ES-135 – parenteral – alopecia – fibroblast growth factor replacement FB-102 – unknown – alopecia areata – interleukin-2 receptor β subunit antagonist HCW-9302 – injection – alopecia areata – interleukin 2 replacement MAX-40070 (MAX-3) – topical – alopecia areata – Janus kinase inhibitor, TYK2 kinase inhibitor MEI-004 – unknown – alopecia – undefined mechanism of action Oxymetazoline (DA-020) – topical – alopecia – α1-adrenergic receptor agonist Phenylephrine/synephrine/tyramine (DA-007) – topical – alopecia – combination of phenylephrine (α1-adrenergic receptor agonist), synephrine (α1-adrenergic receptor agonist), and tyramine (norepinephrine–dopamine releasing agent) YR-001 – topical – alopecia – ion channel antagonist
== Characterization == Nanoparticle drug delivery focuses on maximizing drug efficacy and minimizing cytotoxicity. Fine-tuning nanoparticle properties for effective drug delivery involves addressing the following factors. The surface-area-to-volume ratio of nanoparticles can be altered to allow for more ligand binding to the surface. Increasing ligand binding efficiency can decrease dosage and minimize nanoparticle toxicity. Minimizing dosage or dosage frequency also lowers the mass of nanoparticle per mass of drug, thus achieving greater efficiency. Surface functionalization of nanoparticles is another important design aspect and is often accomplished by bioconjugation or passive adsorption of molecules onto the nanoparticle surface. By functionalizing nanoparticle surfaces with ligands that enhance drug binding, suppress immune response, or provide targeting/controlled release capabilities, both a greater efficacy and lower toxicity are achieved. Efficacy is increased as more drug is delivered to the target site, and toxic side effects are lowered by minimizing the total level of drug in the body. The composition of the nanoparticle can be chosen according to the target environment or desired effect. For example, liposome-based nanoparticles can be biologically degraded after delivery, thus minimizing the risk of accumulation and toxicity after the therapeutic cargo has been released. Metal nanoparticles, such as gold nanoparticles, have optical qualities(also described in nanomaterials) that allow for less invasive imaging techniques.
Time of flight (ToF) is the measurement of the time taken by an object, particle or wave (be it acoustic, electromagnetic, etc.) to travel a distance through a medium. This information can then be used to measure velocity or path length, or as a way to learn about the particle or medium's properties (such as composition or flow rate). The traveling object may be detected directly (direct time of flight, dToF, e.g., via an ion detector in mass spectrometry) or indirectly (indirect time of flight, iToF, e.g., by light scattered from an object in laser doppler velocimetry). Time of flight technology has found valuable applications in the monitoring and characterization of material and biomaterials, hydrogels included.
Sources: en.wikipedia.org
In Cuba, the 26th of July Movement, led by young revolutionaries Fidel Castro and Che Guevara, seized power in the Cuban Revolution on 1 January 1959. Although Fidel Castro's first refused to categorize his new government as socialist and repeatedly denying being a communist, Castro appointed Marxists to senior government and military positions.
=== Documentaries === The 2013 documentary Oxyana covers prescription drug abuse in rural Southern West Virginia, based in the town of Oceana and surrounding Wyoming County, specifically highlight the abuse of oxycodone. In 2017, the short documentary film Heroin(e) was released and nominated for the Academy Award for Best Documentary Short Subject at the 90th Academy Awards. The film focuses on the opioid epidemic's effects on Huntington, West Virginia, where the overdose rate was 10 times the US average. In 2020, Netflix released the documentary series The Pharmacist, which covers the efforts of Dan Schneider, a small-town pharmacist in Poydras, Louisiana, to identify his son's killer and his gathering of evidence against a prolific "pill mill" doctor in New Orleans, leading to an investigation against Purdue Pharma's aggressive corporate sales tactics of OxyContin. In 2021, HBO released The Crime of the Century, a 2-part documentary directed by Alex Gibney that follows the opioid epidemic and the political operatives, government regulations and corporations that enable the abuse of opioids, particularly the Sackler family and Purdue Pharma, and received positive reviews." All the Beauty and the Bloodshed is a 2022 documentary about the activist Nan Goldin's fight against the Sackler family for their role in the opioid epidemic in the United States.. At the 95th Academy Awards, the film was nominated for Best Documentary Feature and was awarded a Peabody Award at the 84th ceremony in 2023.
=== Other risks === Smoking is a risk factor for MS. Similarly, air pollution seems to increase MS risk, as well as the risk of relapses. Organic solvent exposure and night shift work are linked to increased risk of MS, but are not as established as other risk factors. Vaccinations were studied as causal factors; most studies, though, show no association. The risk of developing MS is also weakly associated with obesity, and the presence of certain bacteria such as Akkermansia muciniphila in the intestines.
Protein mass spectrometry refers to the application of mass spectrometry to the study of proteins. Mass spectrometry is an important method for the accurate mass determination and characterization of proteins, and a variety of methods and instrumentations have been developed for its many uses. Its applications include the identification of proteins and their post-translational modifications, the elucidation of protein complexes, their subunits and functional interactions, as well as the global measurement of proteins in proteomics. It can also be used to localize proteins to the various organelles, and determine the interactions between different proteins as well as with membrane lipids. The two primary methods used for the ionization of protein in mass spectrometry are electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI). These ionization techniques are used in conjunction with mass analyzers such as tandem mass spectrometry. In general, the proteins are analyzed either in a "top-down" approach in which proteins are analyzed intact, or a "bottom-up" approach in which protein are first digested into fragments. An intermediate "middle-down" approach in which larger peptide fragments are analyzed may also sometimes be used.
Alkylation of phenol with 2-bromobutyrolactone (2) leads to the ether (3). Oxidation of that product with chromium trioxide then leads to the substituted succinic anhydride (4). Treatment of anhydride with polyphosphoric acid leads to the acylation of the aromatic ring and the formation of the benzopyranone ring (5). The ketone is then selectively reduced by any of several methods, as, for example, conversion to a dithiolane followed by Mozingo reduction to 6. The carboxylic acid is next reduced to the corresponding aldehyde (7) by successive conversion to an acid chloride followed by hydrogenation in the presence of thiophene. A second hydrogenation in the presence of benzylamine leads to the reductive amination product (8). Michael addition of the amino group in 8 to acrylonitrile leads to a 1,4-addition and the formation of (9). Reduction of the nitrile affords the diamine (10). Reaction of this last diamine with tetrahydropyrimidine chloride (11), itself formed by treatment of trimethylene urea with phosphorus oxychloride, leads to the displacement of halogen by the terminal, and thus more accessible, amino group in (10). There is thus formed the serotonergic agent alniditan (12).
Sources: en.wikipedia.org
==== Further impersonation attempts ==== Coinciding with the 2023 Sudan conflict, an account posing as the Rapid Support Forces (RSF) claimed that its leader, Mohamed Hamdan Dagalo, died in the conflict, as the legitimate RSF Twitter account was unverified. Other tweets made by impersonators include an account posing as politician Hillary Clinton declaring a supposed presidential bid in 2024, author J.K. Rowling apologizing for comments she made against transgender people, Pope Francis stating there are "at least three genders", Florida governor Ron DeSandis [sic] calling political donor Kent Sturmon a pedophile, singer Olivia Rodrigo taking credit for a fan-fiction post on Wattpad, and skater Tony Hawk talking about building a skate park in Des Moines, Iowa. Security researcher John Scott-Railton noted a potential rise in impersonation accounts of government agencies, such as Federal Bureau of Investigation (FBI) branches and the United States Citizenship and Immigration Services, as their Twitter accounts are unverified. One tweet, supposedly from cuisine publication The New York Times Cooking, attracted attention for sharing a meme recipe of a hand-shaped M&M cookie atop Greek salad, dubbed "King's Hand". Comedian Kelly Carlin claimed her deceased father—comedian George Carlin, for whom she runs an account—was being impersonated. In a separate instance of impersonation, a parody account for Disney Junior in the United Kingdom was verified as a business.
While the 30-day stunt was not an officially endorsed marketing campaign by Taco Bell, then CEO Mark King later invited Reid to Taco Bell's headquarters in Irvine, California. Reid was also a guest on an official Taco Bell podcast in 2023, discussing the stunt and its effect on his physical health. In 2023, the company test-marketed a vegan Crunchwrap Supreme in Los Angeles, New York, and Orlando to gauge the potential of a national roll out. Bon Appétit tested a vegan Crunchwrap alongside a non-vegan Crunchwrap purchased at the store in midtown Manhattan and said "the differences between the two were also genuinely difficult to discern." On August 29, 2025, the company announced that it would be abrogating its artificial intelligence-powered drive-thrus due to technical difficulties and "trolling," including one instance where a customer ordered 18,000 waters. According to reports, the AI would erroneously tell customers that the store was out of all ingredients except for soda and sauce packets. There were also reports of the AI bots simply disallowing customers to modify their orders, such as replacing meat with beans. The phenomenon quickly became an internet meme. One video on TikTok appeared to show a customer attempting to order McDonald's food items from Taco Bell, which was allowed by the system. Dane Mathews, the chain's Chief Digital and Technology Officer, told the Wall Street Journal: "We’re learning a lot, I’m going to be honest with you. [...] I can tell you it's a very active conversation inside Taco Bell in partnership with our franchisees.
=== Allergy === A study published online in March 2008 showed that Colostrinin is non-allergenic and can prevent allergic inflammation due to common indoor and outdoor allergens. The study used a well characterized mouse model of allergic airway inflammation. Colostrinin (given orally, intranasally or intraperitoneally) significantly decreased IgE/IgG1 production, airway eosinophilia, mucin production and hypersensitivity induced by allergenic extracts from ragweed pollen and house dust mites. In contrast, colostrum induced positive inflammatory responses.
== Side effects == As with all hormonal therapies, GnRH antagonists are commonly associated with hormonal side effects such as hot flushes, headache, nausea and weight gain. When used in fertility treatment they can also be associated with abdominal pain and ovarian hyperstimulation. Subcutaneously administered agents are also associated with injection-site reactions and abarelix (neither of these being GnRH agonists, but instead being antagonists) has been linked with immediate-onset systemic allergic reactions.
The phenomenon of exonization also represents a special case of de novo gene birth, in which, for example, often-repetitive intronic sequences acquire splice sites through mutation, leading to de novo exons. This was first described in 1994 in the context of Alu sequences found in the coding regions of primate mRNAs. Interestingly, such de novo exons are frequently found in minor splice variants, which may allow the evolutionary "testing" of novel sequences while retaining the functionality of the major splice variant(s). Still, it was thought by some that most or all eukaryotic proteins were constructed from a constrained pool of "starter type" exons. Using the sequence data available at the time, a 1991 review estimated the number of unique, ancestral eukaryotic exons to be < 60,000, while in 1992 a piece was published estimating that the vast majority of proteins belonged to no more than 1,000 families. Around the same time, however, the sequence of chromosome III of the budding yeast Saccharomyces cerevisiae was released, representing the first time an entire chromosome from any eukaryotic organism had been sequenced. Sequencing of the entire yeast nuclear genome was then completed by early 1996 through a massive, collaborative international effort. In his review of the yeast genome project, Bernard Dujon noted that the unexpected abundance of genes lacking any known homologs was perhaps the most striking finding of the entire project.
Sources: en.wikipedia.org
The molecule lacks aromatic residues, so it absorbs weakly near 280 nanometres, the wavelength applied to many other peptides. The peptide bond absorbs strongly below 220 nanometres, making 214 nanometres a practical compromise. Gradient methods must therefore use mobile phases with low ultraviolet absorbance to keep the baseline clean.
Neutral and slightly basic aqueous conditions promote aspartimide formation at the aspartate-glycine step, often followed by deamidation. Elevated temperature and repeated freeze-thaw cycles accelerate the loss. Acidic solutions and dry lyophilised powder are comparatively stable over short periods.
No monograph exists in the United States Pharmacopeia or the European Pharmacopoeia, and no widely distributed certified reference standard is available. Purity and identity therefore rest on supplier methods that are not harmonised. This absence is the main reason reported purities are difficult to compare between sources.
No. Epithalamin is a heterogeneous peptide fraction obtained from pineal gland extract and contains many components. Epitalon is a single synthetic tetrapeptide with the sequence Ala-Glu-Asp-Gly. Researchers synthesised the shorter peptide while attempting to identify active sequences within the extract.