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 2025-12-11. Where a claim depends on a specific study, the study is described rather than over-claimed.
Several names circulate for the same molecule, including epitalon, epithalone, epithalamin tetrapeptide, and the sequence code AEDG. A CAS registry number, 307297-39-8, is commonly cited for it, though catalogue entries should be checked against supplier documentation because mislabelled records occur. In its usual form the peptide carries free amino and carboxyl termini and is neither glycosylated nor lipidated. Researchers distinguish the defined tetrapeptide from epithalamin itself, a crude pineal preparation containing many peptides that is not chemically characterised.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Amino acid sequence | Ala-Glu-Asp-Gly | Linear tetrapeptide, also written AEDG |
| Molecular mass | About 390.35 g/mol | Value calculated from the sequence |
| Appearance | White to off-white powder | Lyophilised material forms a loose cake |
| Solubility | Freely soluble in water | Also dissolves in isotonic saline |
| Storage | -20 °C, desiccated | Aliquot solutions to avoid freeze–thaw cycling |
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.
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.
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.
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.
Bauman Moscow State Technical University, founded in 1830, is located in the city center; the university educates 18,000 undergraduate and 1,000 postgraduate students in science and engineering, offering technical degrees.
Relatively strong reducing acids can have antinutrient effects by binding to dietary minerals such as iron and zinc in the gastrointestinal tract and preventing them from being absorbed. Examples are oxalic acid, tannins and phytic acid, which are high in plant-based diets. Calcium and iron deficiencies are not uncommon in diets in developing countries where less meat is eaten and there is high consumption of phytic acid from beans and unleavened whole grain bread. However, germination, soaking, or microbial fermentation are all household strategies that reduce the phytate and polyphenol content of unrefined cereal. Increases in Fe, Zn and Ca absorption have been reported in adults fed dephytinized cereals compared with cereals containing their native phytate.
While it has been shown that the ACD when performing the catalysis uses magnesium and ATP for the formation of the cross-links the specifics of the mechanism are uncertain. Though an interesting aspect of the cross-link formed in this case, is that it uses a non-terminal Glu to ligate to a non-terminal Lys, which seems to be rare in the process of forming an isopeptide bond. Though the chemistry of ACD is still to be resolved, it shows that isopeptide bond formation is not dependent simply on Asp/Asn for non-terminal isopeptide linkages between proteins. The final case to be looked is the curious case of the post translational modifications of microtubilin (MT). MT contains a wide array of post translational modifications; however the two of most regarded interest are polyglutamylation and polyglycylation. Both modifications are similar in the sense they are repeating stretches of the same amino acid fused to the side chain carboxyl group of glutamate at the c-terminal region of the MT. The enzymatic mechanisms are not fully fleshed out as not much is known about the polyglycating enzyme. In the case of polyglutamylation the exact mechanism is also unknown, but it does seem to be ATP-dependent. Though again there is a lack of clarity in regard to the enzymatic chemistry, there is still valuable insight in the formation of isopeptide bonds using the R-group carboxyl of Glu in conjunction with the N-terminal amino of the modifying peptides.
A formal announcement of his victory took place on December 12, 2014, with Shumlin and other supporters on the Statehouse steps. His public fight drew regional and national attention, the support of Shumlin, and a team of pro-bono law students from the University of New Hampshire legal clinic. After 22 years with The Richards Group, Chick-fil-A switched to McCann New York in 2016. Along with the cows, ads included famous people in history in a campaign called "Chicken for Breakfast. It's not as crazy as you think."
It insured the lives of its members for $1,000 and that of members' wives for half that amount. Sick benefits were administered by the subordinate lodges and death benefits by the Supreme Lodge. The ritual was based on the covenant between God, Noah, Abraham, and Moses. The emblem was the All Seeing Eye above three pillars with the tablets of the Ten Commandments between them. Independent Order of B'rith Abraham - Founded in 1887 as a split from the Order of Brith Abraham, whose leadership they felt was incompetent. Some sources give the name as the Improved Order of B'rith Abraham. Admitted women and was smoothly run. Added social membership option to what was already essentially an insurance society in 1924. Had a peak membership of 206,000 in 1917. In 1923 it had 585 lodges and a benefit membership of 142,812. Had 58,000 immediately before World War II. Changed name to simply B'rith Abraham in 1968. Merged with B'nai Zion in 1981. Headquarters in 1923 at 37 Seventh Street New York City. New York was still the headquarters in 1979. The Order's stated objectives in 1969 were to "foster fraternity in the context of Jewish ideals, tradition, and welfare", provide fraternal benefits to its members, and support programs for underprivileged children and seniors. It also promoted Zionism. Independent Order of American Israelites - Founded in 1894 in New York City by a group of men, some or all of whom had been members of the Independent Order, Free Sons of Israel, and the Sons of Benjamin. Order paid a $1,000 death benefit for male members and $500 for female members.
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Isotope analysis has many applications in archaeology, from dating sites and artefacts, determination of past diets and migration patterns and for environmental reconstruction. Information is determined by assessing the ratio of different isotopes of a particular element in a sample. The most widely studied and used isotopes in archaeology are carbon, oxygen, nitrogen, strontium and calcium. An isotope is an atom of an element with an abnormal number of neutrons, changing their atomic mass. Isotopes can be subdivided into stable and unstable or radioactive. Unstable isotopes decay at a predictable rate over time. The first stable isotope was discovered in 1913, and most were identified by the 1930s. Archaeology was relatively slow to adopt the study of isotopes. Whereas chemistry, biology and physics, saw a rapid uptake in applications of isotope analysis in the 1950s and 1960s, following the commercialisation of the mass spectrometer. It wasn't until the 1970s, with the publication of works by Vogel and Van Der Merwe (1977) and DeNiro and Epstein (1978; 1981) that isotopic analysis became a mainstay of archaeological study.
=== Fuels === Another use of cryogenics is cryogenic fuels for rockets with liquid hydrogen as the most widely used example, with liquid methane starting to become more prevalent in recent years. Liquid oxygen (LOX) is even more widely used but as an oxidizer, not a fuel. NASA's workhorse Space Shuttle used cryogenic hydrogen/oxygen propellant as its primary means of getting into orbit. LOX is also widely used with RP-1 kerosene, a non-cryogenic hydrocarbon, such as in the rockets built for the Soviet space program by Sergei Korolev. Russian aircraft manufacturer Tupolev developed a version of its popular design Tu-154 with a cryogenic fuel system, known as the Tu-155. The plane uses a fuel referred to as liquefied natural gas or LNG, and made its first flight in 1989.
A March 2020 report by ProPublica revealed that Walmart used its political influence with the Trump administration to avoid criminal prosecution for over-dispensing opioids in Texas. In July 2020, Indivior Solutions, Indivior Inc., and Indivior plc agreed to pay $600 million to resolve liability related to false marketing of Suboxone to MassHealth for use by patients with children under the age of six years old. Additionally, Indivior Solutions pled guilty to one-count of felony information. On December 15, 2025, Trump signed an executive order classifying fentanyl as a "weapon of mass destruction".
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RCH2=CH2CO-CoA + NADPH + H+ The two substrates of this enzyme are an acyl-CoA and oxidised nicotinamide adenine dinucleotide phosphate (NADP+). Its products are the corresponding 2,3-dehydroacyl-CoA, reduced NADPH, and a proton. The enzyme does not alter the length of the chain attached to coenzyme A but creates a double bond adjacent to the carbonyl group. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is acyl-CoA:NADP+ 2-oxidoreductase. Other names in common use include 2-enoyl-CoA reductase, dehydrogenase, acyl coenzyme A (nicotinamide adenine dinucleotide, phosphate), enoyl coenzyme A reductase, crotonyl coenzyme A reductase, crotonyl-CoA reductase, and acyl-CoA dehydrogenase (NADP+).
=== Research applications === Ribosomal proteins: For the studies of individual ribosomal proteins, the use of proteins that are produced and purified from recombinant sources has largely replaced those that are obtained through isolation. However, isolation is still required for the studies of the whole ribosome. Lysosomal proteins: Lysosomal proteins are difficult to produce recombinantly due to the number and type of post-translational modifications that they have (e.g. glycosylation). As a result, recombinant lysosomal proteins are usually produced in mammalian cells. Plant cell culture was used to produce FDA-approved glycosylated lysosomal protein-drug, and additional drug candidates. Recent studies have shown that it may be possible to produce recombinant lysosomal proteins with microorganisms such as Escherichia coli and Saccharomyces cerevisiae. Recombinant lysosomal proteins are used for both research and medical applications, such as enzyme replacement therapy.
== Career == In 1981, Valko joined the Hungarian Academy of Sciences, where she took on multiple roles, including heading the chromatography research group at the Central Research Institute for Chemistry of the Hungarian Academy of Sciences. Concurrently, she also served as a research scientist at the Institute of Enzymology from 1981 to 1985. Between 1993 and 1995, she worked as a senior research analytical chemist at Wellcome Research Laboratory. Subsequently, she held a position as a research investigator at GlaxoWellcome Medicines Research Centre from 1995 to 2000. From 2000 to 2015, she served as the senior research investigator at the Physicochemical Characterization Group at GlaxoSmithKline. In 2017, she founded Bio-Mimetic Chromatography and has been serving as its director since then. Later in 2019, she established Bio-Mimetic Cosmetics as a trading branch of Bio-Mimetic Chromatography. From 1977 to 1981, Valko served as a lecturer in the Department of Pharmaceutical Chemistry at Semmelweis University. Additionally, she held a Mappletorpe research fellowship in the School of Pharmacy at the University of London from 1991 to 1993. Since 2004, she has held the position of honorary professor at the University College London School of Pharmacy.
Sources: en.wikipedia.org
It is a synthetic tetrapeptide. Its sequence was derived from research on peptide fractions of bovine pineal extract, and the intact AEDG sequence has not been demonstrated as an abundant free peptide in human tissue.
AEDG is the one-letter code for the four amino acids alanine, glutamate, aspartate and glycine in that order. The same molecule is written in three-letter form as Ala-Glu-Asp-Gly.
Identity is normally confirmed by mass spectrometry against the calculated mass of roughly 390.35 g/mol. Purity is then estimated by reversed-phase high-performance liquid chromatography with ultraviolet detection.
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.