This is a working overview of Tetrapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-02-21. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C14H22N4O9 | Free acid form of the tetrapeptide |
| Molecular mass | About 390.35 Da | Calculated monoisotopic value |
| Appearance | White to off-white powder | Typical lyophilized presentation |
| Solubility | Soluble in water | Also dissolves in buffered saline |
| Storage temperature | Minus 20 degrees Celsius | Dry, dark conditions; avoid repeated thawing |
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.
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.
The molecule is a short, linear, hydrophilic peptide that dissolves readily in water or aqueous buffer. Its principal chemical liabilities are hydrolytic rather than oxidative, since it contains no cysteine, methionine, or tryptophan residues. The aspartate–glycine step is a recognised site for aspartimide formation under mildly acidic or basic conditions, generating isoaspartate and succinimide-related products over time. Desiccated lyophilised powder held at −20 °C is comparatively stable, whereas dilute solutions degrade faster and are best frozen as single-use aliquots rather than thawed repeatedly.
No pharmacopoeial monograph exists for this peptide, so quality rests on the supplier's internal specifications and on whatever independent testing a purchaser arranges. Certificates of analysis differ widely in which tests they report and in the limits applied. The counter-ion introduced during purification, commonly acetate or trifluoroacetate, changes the net peptide content of a given mass of powder, so two samples of equal weight may not contain equal amounts of the active sequence. Third-party laboratories can verify purity, identity, residual solvents, and counter-ion content for a fee, which makes documentation more informative than labelling.
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.
Epitalon is a synthetic linear tetrapeptide with the sequence alanine–glutamate–aspartate–glycine, abbreviated AEDG. Its molecular formula is C14H22N4O9 and the calculated mass is approximately 390.35 g/mol. The compound is made by solid-phase peptide synthesis rather than extracted from tissue, although early work described it as a short fragment of a peptide fraction obtained from bovine pineal extract. In the research literature the spelling epitalon and the variant epithalone both appear, while AEDG is the standard code used in peptide nomenclature.
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.
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.
The results of the work at Duke were impressive with one treated bird recovering to the point of being able to fly again. This was followed by the production of clinical-grade alpha-glucosidase in Chinese hamster ovary (CHO) cells and in the milk of transgenic rabbits. This work eventually culminated in the start of clinical trials with the first clinical trial including four babies receiving enzyme from rabbit milk at Erasmus MC Sophia Children's Hospital and three babies receiving enzyme grown in CHO cells at Duke University in 1999. The currently approved Myozyme is manufactured by Genzyme Corp. in Cambridge, Massachusetts. Its development was a complex process. Genzyme first partnered with Pharming Group NV which had managed to produce acid alpha-glucosidase from the milk of transgenic rabbits. They also partnered with a second group based at Duke University using Chinese hamster ovary cells. In 2001, Genzyme acquired Novazyme which was also working on this enzyme. Genzyme also had its product (Myozyme) grown in CHO cells under development. In November 2001, Genzyme chief executive Henri Termeer organised a systematic comparison of the various potential drugs in a mouse model of Pompe disease. It was found that the Duke enzyme was the most efficacious, followed by Myozyme. However, due to easier manufacture of Myozyme, work on the other products was discontinued.
He was also president of the family's principal philanthropy run by family members, the Rockefeller Brothers Fund, from its inception in 1940 to 1956. In 1929, he joined the family's renowned Rockefeller Foundation; elected to the board in 1931 he subsequently became chairman of this major philanthropic organization for twenty years and was responsible for changing the focus of the institution. The principal philanthropic institution he created was the JDR III Fund in 1963, its major program being the Asian Cultural Program, created in 1967 to encourage East-West cultural exchange. The Fund was wound-up upon his death in 1979, but the Cultural Program continued as the Asian Cultural Council, which has provided grant assistance to more than 4,000 Asians and Americans in the area of the arts. Funding for its programs is derived from a combination of endowment income and contributions from individuals, foundations and corporations in the United States and Asia. In the mid-1950s, John III assumed the leadership of the Exploratory Committee for a Musical Arts Center, a committee of civic leaders who were working to create what would become Lincoln Center. He was the key figure in the fund-raising efforts and in forging a consensus among the civic leaders and others who were essential to its success. The Center itself was built over a period from 1959 to 1969. He was its second president, commencing in 1956, and he became its chairman in 1961. He was chairman until 1970 when he was duly elected honorary chairman.
One weakness of these measures is that they are not good indicators of liver vitamin A stores as retinyl esters in hepatic stellate cells. The amount of vitamin A leaving the liver, bound to retinol binding protein (RBP), is under tight control as long as there are sufficient liver reserves. Only when liver content of vitamin A drops below approximately 20 μg/gram will concentration in the blood decline.
Sources: en.wikipedia.org
== Further reading == Schmidt, Eckart W. (2022). "1,3,5,7-Tetranitro-1,3,5,7-tetraazacyclooctane, Octogen (HMX)". Nitramines. Encyclopedia of Liquid Fuels. De Gruyter. pp. 4327–4371. doi:10.1515/9783110750287-035. ISBN 978-3-11-075028-7.
He played the remainder of the season, managing thirteen matches for the year and was rewarded with the club rising star award as the best young player. At the end of the year he changed guernsey numbers from 43 to 1.
The numbers 1.930 and 0.537 are phenomenological; these specific values provide a fairly good fit to the data. The product Re√fD (called the "friction Reynolds number") can be considered, like the Reynolds number, to be a (dimensionless) parameter of the flow: at fixed values of Re√fD, the friction factor is also fixed. In the Kármán–Prandtl resistance equation, fD can be expressed in closed form as an analytic function of Re through the use of the Lambert W function:
Sources: en.wikipedia.org
=== Isotope effects === Isotope peaks within a spectrum can help in structure elucidation. Compounds containing halogens (especially chlorine and bromine) can produce very distinct isotope peaks. The mass spectrum of methylbromide has two prominent peaks of equal intensity at m/z 94 (M) and 96 (M+2) and then two more at 79 and 81 belonging to the bromine fragment. Even when compounds only contain elements with less intense isotope peaks (carbon or oxygen), the distribution of these peaks can be used to assign the spectrum to the correct compound. For example, two compounds with identical mass of 150 Da, C8H12N3+ and C9H10O2+, will have two different M+2 intensities which makes it possible to distinguish between them.
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February 21, 2011 Thailand Thailand's GDP rose 3.8% in the fourth quarter of 2010 after a minor recession caused by GDP contractions of 0.4% in the second quarter and 0.3% in the third quarter of 2010. The growth of the fourth quarter was attributed to a strengthening global economy, along with increasing income levels in the nation and greater liquidity by financial institutions to help the private sector. Full-year growth was recorded at 7.8%.
=== AIDS === It seems that Th22 cells could play a protective role in patients with AIDS. CCR5 and α4β7 molecules expressed by Th22 cells were able to bind to the circulating HIV receptor, and thus via interleukin-22 (IL-22) production protect against intestinal epithelial damage, leading to a mechanism of resistance against HIV-induced destruction of epithelial cell integrity.
Sources: en.wikipedia.org
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.
No naturally occurring free form of the peptide has been described. The four-amino-acid sequence can appear as a fragment within larger proteins, but that is not the same as the intact compound being present as a circulating molecule. Materials used in research are synthetic.
Purity is usually checked by reverse-phase high-performance liquid chromatography, which separates the target peptide from related impurities. Mass spectrometry is commonly used alongside it to confirm molecular mass. Some suppliers also provide amino acid analysis for additional sequence confirmation.
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.