If you have been reading about reversed-phase HPLC and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-07-26. Numbers and descriptions here follow the published literature rather than marketing material.
Storage practice centres on limiting moisture, oxygen, and repeated temperature cycling. Freeze-dried powder is generally held desiccated at minus twenty degrees Celsius or colder and protected from light. Reconstituted solutions are markedly less stable, and the aspartate-glycine junction is prone to succinimide formation at neutral to mildly alkaline pH. Portioning material into single-use aliquots reduces degradation compared with repeated freeze-thaw cycles. Stability data specific to this tetrapeptide remain scarce, so most handling guidance is extrapolated from general peptide chemistry rather than measured directly.
Documentation accompanying research peptides usually includes a certificate of analysis listing the batch number, purity figure, and test methods applied. Buyers comparing suppliers should check whether the reported purity refers to chromatographic area or to a mass-balance calculation, because the two are not equivalent. Counter-ion content, residual solvents, and water content are sometimes omitted from such certificates even though they affect the actual peptide mass present. Independent verification through a second laboratory is the most direct way to confirm that a supplied material matches its label.
Purity assessment of peptide reagents normally relies on reversed-phase high-performance liquid chromatography. A gradient of acetonitrile in water with trifluoroacetic acid, paired with a C18 stationary phase, separates the target tetrapeptide from truncated sequences and deletion analogues. Detection at 214 nanometres exploits absorbance of the peptide backbone, since the molecule contains no aromatic residue. Results are expressed as a percentage of total peak area. Values above ninety-five percent are typical for research-grade material, although reporting conventions vary between suppliers.
Storage recommendations center on limiting moisture, heat, and light. The dry powder is generally kept at minus 20 degrees Celsius, and some suppliers recommend minus 80 degrees for long-term archival. Once dissolved, solutions are usually aliquoted and frozen to avoid repeated freeze-thaw cycles, which can promote aggregation or degradation. Aqueous stability depends on pH and concentration, and buffered saline is often preferred over plain water for biological work. Stability data specific to epitalon remain limited, so general peptide-handling practices are applied by analogy rather than from product-specific validation.
Epitalon is a synthetic tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, abbreviated AEDG. Its molecular formula is C14H22N4O9 and its calculated monoisotopic mass is approximately 390.35 daltons. The compound does not occur naturally as a free peptide; it is produced by solid-phase peptide synthesis. Because it contains two acidic residues and no basic residues, the neutral form carries a net negative charge at physiological pH. This charge profile influences how the peptide behaves in solution and during chromatographic analysis.
Laboratory-grade epitalon is typically supplied as a lyophilized powder. Purity is commonly assessed with reverse-phase high-performance liquid chromatography, often paired with mass spectrometry to confirm molecular identity. Amino acid analysis and peptide mapping can provide additional confirmation of sequence. Certificates of analysis for research materials frequently report purity above 95 percent, although the methods behind such figures vary between suppliers. The absence of a pharmacopeial monograph means that no single standardized assay defines the compound, so reported results depend on the analytical protocol chosen.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Freeze-dried solid |
| Solubility class | Freely soluble in water | Aqueous buffers also suitable |
| Typical storage temperature | Minus 20 degrees Celsius or colder | Desiccated and light protected |
| Typical analytical method | RP-HPLC with UV detection | 214 nm on C18 column |
| Identity confirmation | Electrospray mass spectrometry | Sequence verified separately |
Regulatory status varies by country and is not harmonized. Epitalon is not an approved drug in major Western jurisdictions. In some countries it is sold as a research chemical, and in others it has appeared in products marketed for other categories. This inconsistent status means that purity, labeling accuracy, and documentation differ widely between suppliers, and verification of identity and purity through independent analysis is the usual way buyers assess a given lot.
Epitalon appears in the literature primarily through a small number of research groups, most of them associated with the St. Petersburg Institute of Bioregulation and Gerontology. Publications describe cell culture experiments, animal studies, and a limited number of small human studies. Independent replication outside this network is sparse. As a result, reviews of the topic usually separate descriptive reports of observed effects from the question of whether those effects generalize, and they note the difficulty of comparing studies that use different preparations and endpoints.
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.
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.
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.
=== Mental health === Women with PMOS are far more likely to have depression than women without PMOS. Symptoms of depression might be heightened by certain symptoms of the condition, such as hirsutism or obesity, that can lead to low self-esteem or poor body image. Screening for depression and anxiety disorders is recommended using validated questionnaires, for instance, at diagnosis as well as afterwards, based on clinical judgement. For eating disorders and body image distress, screening is only recommended when clinically indicated. For sexually active women who give permission to discuss it, psychosexual dysfunction can be assessed too. Treatment of PMOS shows no to moderate effect on depression or anxiety, and standard therapies (such a psychotherapy and antidepressants) are recommended instead. Cognitive behaviour therapy can be used for girls and women with low self-esteem, poor body image, disordered eating or psychosexual dysfunction.
Knowing that large-scale production for medical use was futile in a laboratory, the Oxford team tried to convince the war-torn British government and private companies to engage in mass production, but the initial response was muted. Dr Blount, director of research at Glaxo Laboratories, wrote to Florey at Oxford in September 1940 but received no reply. It appeared that Florey had already appealed for assistance to two British pharmaceutical companies but had been turned down by them, and had become disillusioned with the British pharmaceutical industry. In April 1941, Warren Weaver met with Florey, and they discussed the difficulty of producing sufficient penicillin to conduct clinical trials. Weaver arranged for the Rockefeller Foundation to fund a three-month visit to the United States for Florey and a colleague to explore the possibility of production of penicillin there. Florey and Heatley left for the United States by air on 27 June 1941. Knowing that mould samples kept in vials could be easily lost, they smeared their coat pockets with the mould. Florey met with neurophysiologist John Fulton, who introduced him to Ross Harrison, the Chairman of the National Research Council (NRC). Harrison referred Florey to Thom, the chief mycologist at the Bureau of Plant Industry of the United States Department of Agriculture (USDA) in Beltsville, Maryland, and the man who had identified the mould reported by Fleming.
==== Remoting ==== Component methods may be made available as web services with no additional coding and configuration. All that is required is for a method's access to be declared 'remote'. ColdFusion automatically generates a WSDL at the URL for the component in this manner: http://path/to/components/Component.cfc?wsdl. Aside from SOAP, the services are offered in Flash Remoting binary format. Methods which are declared remote may also be invoked via an HTTP GET or POST request. Consider the GET request as shown.
The 25-NB (25x-NBx) series, or NBOMe series, also known as the N-benzylphenethylamines, is a family of serotonergic psychedelics. They are substituted phenethylamines and were derived from the 2C family. The most commonly encountered NBOMe drugs are 25I-NBOMe, 25B-NBOMe, and 25C-NBOMe. The NBOMe drugs act as selective agonists of the serotonin 5-HT2 receptors. The 25-NB family is unique relative to other classes of psychedelics in that they are, generally speaking, extremely potent and quite selective for the 5-HT2 receptors. Use of NBOMe series drugs has caused many deaths and hospitalisations since the drugs popularisation in the 2010s. This is primarily due to their high potency, unpredictable pharmacokinetics, and sellers passing off the compounds in the series as LSD.
Frederic Durán-Jordà fled to Britain in 1938 and worked with Dr Janet Vaughan at the Royal Postgraduate Medical School at Hammersmith Hospital to establish a system of national blood banks in London. With the outbreak of war appearing imminent in 1938, the War Office created the Army Blood Supply Depot (ABSD) in Bristol, headed by Lionel Whitby and in control of four large blood-depots around the country. British policy through the war was to supply military personnel with blood from centralized depots, in contrast to the approach taken by the Americans and Germans where troops at the front were bled to provide required blood. The British method proved more successful in adequately meeting all requirements, and over 700,000 donors were bled over the course of the war. This system evolved into the National Blood Transfusion Service established in 1946, the first national service to be implemented.
Sources: en.wikipedia.org
=== Steps of the urea cycle === Carbamoyl phosphate is converted to citrulline. With catalysis by ornithine transcarbamylase, the carbamoyl phosphate group is donated to ornithine and releases a phosphate group. A condensation reaction occurs between the amino group of aspartate and the carbonyl group of citrulline to form argininosuccinate. This reaction is ATP dependent and is catalyzed by argininosuccinate synthetase. Argininosuccinate undergoes cleavage by argininosuccinase to form arginine and fumarate. Arginine is cleaved by arginase to form urea and ornithine. The ornithine is then transported back to the mitochondria to begin the urea cycle again.
=== Early life and education === Martin Litchfield West was born on 23 September 1937 at Eltham General Hospital (Eltham, London), the elder child (there being a younger daughter, Dr Jennifer Bywaters) of civil engineer Maurice Charles West and Catherine Baker, née Stainthorpe. His parents lived at that time in Orpington, but moved in 1939 to Hampton, where his father was appointed resident engineer at the Metropolitan Water Board-operated waterworks. West's father's family were from the Home Counties, and his mother's family from Yorkshire and Durham. His paternal grandfather, Robert West, lectured in electrical engineering; his maternal grandfather, John Stainthorpe, was a railwayman from Pickering. Litchfield was the maiden name of his paternal grandmother. Aged four, West entered the private preparatory school of Denmead. At 11, he lost a scholarship at Colet Court (now St Paul's Juniors), but was offered a feepaying place instead. West discovered at Colet his interest in languages and invented at 14 a competitor of Esperanto he labelled 'Unilingua'. In 1951, he won a scholarship to the main school, St Paul's. Excelling at both linguistics and mathematics, he was advanced to the 'Upper Eighth' and sat for a scholarship to Balliol College a year early. His tutors included Donald Russell, Michael Stokes and Russell Meiggs. Among his peers were future Nobel Prize winner Anthony J. Leggett, and future Permanent Secretary Peter Gregson.
=== Absorption === Vitamin K is absorbed through the jejunum and ileum in the small intestine. The process requires bile and pancreatic juices. Estimates for absorption are on the order of 80% for vitamin K1 in its free form (as a dietary supplement) but much lower when present in foods. For example, the absorption of vitamin K from kale and spinach – foods identified as having a high vitamin K content – are on the order of 4% to 17% regardless of whether raw or cooked. Less information is available for absorption of vitamin K2 from foods. The intestinal membrane protein Niemann–Pick C1-like 1 (NPC1L1) mediates cholesterol absorption. Animal studies show that it also factors into absorption of vitamins E and K1. The same study predicts potential interaction between SR-BI and CD36 proteins as well. The drug ezetimibe inhibits NPC1L1 causing a reduction in cholesterol absorption in humans, and in animal studies, also reduces vitamin E and vitamin K1 absorption. An expected consequence would be that administration of ezetimibe to people who take warfarin (a vitamin K antagonist) would potentiate the warfarin effect. This has been confirmed in humans.
Raleigh's all-time record high temperature is 106 °F (41 °C) on July 5, 2024, while the all-time record low is −9 °F (−23 °C) on January 21, 1985. Raleigh falls in USDA hardiness zones 7b (5 °F to 10 °F) and 8a (10 °F to 15 °F).
==== MeSH D06.472.334 – gonadal hormones ==== MeSH D06.472.334.500 – activins MeSH D06.472.334.500.500 – inhibin-beta subunits MeSH D06.472.334.734 – corpus luteum hormones MeSH D06.472.334.734.623 – progesterone MeSH D06.472.334.734.769 – relaxin MeSH D06.472.334.851 – gonadal steroid hormones MeSH D06.472.334.851.437 – estradiol congeners MeSH D06.472.334.851.437.249 – equilenin MeSH D06.472.334.851.437.374 – equilin MeSH D06.472.334.851.437.500 – estradiol MeSH D06.472.334.851.437.750 – estriol MeSH D06.472.334.851.437.750.320 – estetrol MeSH D06.472.334.851.437.968 – estrogenic steroids, alkylated MeSH D06.472.334.851.437.968.500 – ethinyl estradiol MeSH D06.472.334.851.437.968.500.250 – ethinyl estradiol-norgestrel combination MeSH D06.472.334.851.437.968.500.500 – mestranol MeSH D06.472.334.851.437.968.500.750 – quinestrol MeSH D06.472.334.851.437.984 – estrogens, catechol MeSH D06.472.334.851.437.984.350 – hydroxyestrones MeSH D06.472.334.851.437.988 – estrogens, conjugated (usp) MeSH D06.472.334.851.437.994 – estrogens, esterified (usp) MeSH D06.472.334.851.437.996 – estrone MeSH D06.472.334.851.687 – progesterone congeners MeSH D06.472.334.851.687.500 – pregnenolone MeSH D06.472.334.851.687.500.500 – 17-alpha-hydroxypregnenolone MeSH D06.472.334.851.687.750 – progesterone MeSH D06.472.334.851.687.750.074 – 20-alpha-dihydroprogesterone MeSH D06.472.334.851.687.750.099 – 5-alpha-dihydroprogesterone MeSH D06.472.334.851.687.750.478 – hydroxyprogesterones MeSH D06.472.334.851.687.750.478.400 – 17-alpha-hydroxyprogesterone MeSH D06.472.334.851.687.750.478.400.500 – pregnanetriol MeSH D06.472.334.851.687.750.739 – pregnanediol MeSH D06.472.334.851.968 – testosterone congeners MeSH D06.472.334.851.968.500 – androstane-3,17-diol MeSH D06.472.334.851.968.750 – androstenediol MeSH D06.472.334.851.968.875 – androstenedione MeSH D06.472.334.851.968.937 – androsterone MeSH D06.472.334.851.968.952 – dehydroepiandrosterone MeSH D06.472.334.851.968.952.300 – dehydroepiandrosterone sulfate MeSH D06.472.334.851.968.964 – dihydrotestosterone MeSH D06.472.334.851.968.968 – etiocholanolone MeSH D06.472.334.851.968.976 – nandrolone MeSH D06.472.334.851.968.984 – testosterone MeSH D06.472.334.851.968.984.500 – epitestosterone MeSH D06.472.334.851.968.984.750 – testosterone propionate MeSH D06.472.334.968 – inhibins MeSH D06.472.334.968.500 – inhibin-beta subunits MeSH D06.472.334.984 – testicular hormones
Sources: en.wikipedia.org
Reversed-phase high-performance liquid chromatography with ultraviolet detection at 214 nanometres is the usual approach. Peak area percentage provides a purity figure relative to other components in the sample. Mass spectrometry is then applied to confirm identity.
Aspartate can cyclise into a succinimide intermediate that later hydrolyses back as isoaspartate. Both forms share the same molecular mass, so mass spectrometry alone cannot tell them apart. This shapes how purity data should be interpreted.
Freeze-dried material is normally kept desiccated below minus twenty degrees Celsius and shielded from light. Solutions are prepared shortly before use and held cold. Repeated thawing is avoided because it accelerates aggregation and degradation.
Epitalon is a synthetic tetrapeptide built from four amino acids: alanine, glutamate, aspartate, and glycine. It is not extracted from a natural source but made in the laboratory by chemical synthesis. Its short length makes it relatively straightforward to produce at high purity.