The short version of lyophilised powder fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-01-05 and is reviewed periodically as new material appears.
Identity and purity are checked by reversed-phase high-performance liquid chromatography, usually with ultraviolet detection near 214 nanometres, where the peptide bond absorbs. Mass spectrometry confirms the expected mass and reveals whether truncation products or adducts are present. Acid hydrolysis followed by amino acid analysis gives the residue ratio, which should approximate one alanine, one glutamate, one aspartate and one glycine. Counter-ions such as acetate or trifluoroacetate remain in the dried product and lower net peptide content, so a stated purity figure on a label does not by itself describe how much peptide a vial holds.
Regulatory treatment differs by country. No formulation of epitalon holds a marketing authorisation as a medicine in the United States or the European Union, where material sold for laboratory use is handled as a research chemical and is not intended for human consumption. In Russia, several short peptide preparations from the same institute's peptide series are registered medicinal products, and epitalon appears in that national context. Elsewhere it is frequently offered as a cosmetic ingredient, a category with lighter requirements. Advertising claims about longevity or disease prevention are restricted in most jurisdictions, which limits how sellers describe the compound.
Freeze-dried epitalon is normally kept at minus twenty degrees Celsius in a sealed, desiccated container, protected from light. Short excursions at ambient temperature during shipping are generally tolerated, but repeated warming and cooling cycles encourage moisture uptake, which shortens shelf life. Once dissolved, the peptide is far less stable than the solid: aqueous solutions are subject to hydrolysis and to deamidation at the aspartate and glutamate residues. Working solutions are therefore held refrigerated and used within days, and repeated freezing and thawing of the same vial is best avoided.
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.
| Property | Value | Notes |
|---|---|---|
| Storage temperature, solid | Approximately -20 C | Sealed, desiccated, protected from light |
| Typical identity method | Electrospray mass spectrometry | Protonated ion expected near 391 |
| Typical purity method | Reversed-phase HPLC | Ultraviolet detection near 214 nm |
| Common synonyms | Epithalon, epithalone, AEDG | Spelling variants appear in supplier catalogues |
| Solution stability | Days at 2-8 C | Hydrolysis and deamidation limit shelf life |
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 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.
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.
Identity is normally established by reversed-phase high-performance liquid chromatography combined with mass spectrometry, a pairing that separates components and confirms molecular mass at once. Purity is quoted as a percentage from the chromatogram, and figures above ninety-five percent are a frequent commercial specification. Amino acid analysis or sequencing supplies further confirmation when required. Because many short peptides behave similarly under chromatography, retention time alone does not establish sequence; the mass measurement is what separates one tetrapeptide from another, and certificates should report both.
Short peptides such as AEDG are normally supplied as a freeze-dried solid and are kept dry, cold, and shielded from light. Holding at minus twenty degrees Celsius is common for the long term, while a refrigerator suffices for brief periods before use. The material takes up moisture to some degree, so containers should stay sealed and be allowed to reach room temperature before opening, which limits condensation on the contents. Repeated warming and cooling of a single container is discouraged because it admits water and can lower the amount of intact peptide.
Engrafting an immunodeficient mouse with functional human cells can be achieved by intravenous injections of human cells and tissue into the mouse, and/or creating a genetically modified mouse from human genes. These models have been instrumental in studying human diseases, immune responses, and therapeutic interventions. This section highlights the various humanized mice models developed using the different methods.
== Further reading == Craigie, W.A.; Bradley, H. (1914). "Realgar". In Sir James, A.H. Murray (ed.). A New English Dictionary on Historical Principles. Clarendon Press at Oxford. p. 202 – via archive.org. William Mesny (1899). Mesny's Chinese Miscellany. A Text Book of Notes on China and the Chinese. Vol. III. Shanghai. p. 251. William Mesny (1905). Mesny's Chinese Miscellany. A Text Book of Notes on China and the Chinese. Vol. IV. Shanghai. pp. 425–426.
== Structural architectures of proteins with β-sheets == β-sheets are present in all-β, α+β and α/β domains, and in many peptides or small proteins with poorly defined overall architecture. All-β domains may form β-barrels, β-sandwiches, β-prisms, β-propellers, and β-helices.
King Sebastian of Portugal feared rampant slavery was having a negative effect on Catholic proselytization, so he commanded that it be banned in 1571. Hideyoshi was so disgusted that his own Japanese people were being sold en masse into slavery on Kyushu, that he wrote a letter to Jesuit Vice-Provincial Gaspar Coelho on July 24, 1587, to demand the Portuguese, Siamese (Thai), and Cambodians stop purchasing and enslaving Japanese and return Japanese slaves who ended up as far as India. Hideyoshi blamed the Portuguese and Jesuits for this slave trade and banned Christian proselytizing as a result. In 1595, a law was passed by Portugal banning the selling and buying of Chinese and Japanese slaves.
S2CID 17336375. Wickramasinghe, N. C. (2010). "The astrobiological case for our cosmic ancestry". International Journal of Astrobiology. 9 (2): 119–129. Bibcode:2010IJAsB...9..119W. doi:10.1017/S1473550409990413. S2CID 13978227. Wickramasinghe, N.C.; Wallis, J.; Wallis, D.H.; Schild, R.E.; Gibson, C.H. (2012). "Life-bearing planets in the solar vicinity". Astrophysics and Space Science. 341 (2): 295–9. Bibcode:2012Ap&SS.341..295W. doi:10.1007/s10509-012-1092-8. S2CID 120484953. Chandra Wickramasinghe, A Journey with Fred Hoyle: The Search for Cosmic Life, World Scientific Publishing, 2005, ISBN 981-238-912-1 Janaki Wickramasinghe, Chandra Wickramasinghe and William Napier, Comets and the Origin of Life, World Scientific Publishing, 2009, ISBN 981-256-635-X Chandra Wickramasinghe and Daisaku Ikeda, Space and Eternal Life, Journeyman Press, 1998, ISBN 1-85172-060-X
Sources: en.wikipedia.org
In organic chemistry, a carbamate is a category of organic compounds with the general formula R2NC(O)OR and structure >N−C(=O)−O−, which are formally derived from carbamic acid (NH2COOH). The term includes organic compounds (e.g., the ester ethyl carbamate), formally obtained by replacing one or more of the hydrogen atoms by other organic functional groups; as well as salts with the carbamate anion H2NCOO− (e.g. ammonium carbamate). Polymers whose repeat units are joined by carbamate like groups −NH−C(=O)−O− are an important family of plastics, the polyurethanes.
== Partnerships == Towards fulfilling its mandate, RCB is collaborating with various national and international institutions of repute. The partnerships are meant for exchange of ideas, information sharing, training, networking, conducting scientific colloquia, workshops, academic exchange programmes and student study visits within (and outside) India and for students of the Asia-Pacific region. RCB and National Institute of Advanced Industrial Science and Technology (AIST), Japan announced a partnership to further capacity building initiatives in bio-imaging and biotechnology. The agreement offers an excellent opportunity for both the institutions in capacity building, training and research collaborations, benefitting young scientists not only in India and Japan, but also from the UNESCO member countries in the Asia-Pacific and SAARC regions. In its continuing effort to fulfill the core mandate, RCB is actively engaged in a range of research and related activities in partnership with other academic institutions, which form part of the NCR Biotech Science Cluster, Faridabad. Shared facilities such as Advanced Technology Platform Centre (ATPC), and Bioincubators (supported by Biotechnology Industry Research Assistance Council (BIRAC)), which is meant to support the budding biotechnology entrepreneurs, are being established.
== Measurement techniques == Standard organic geochemical methods are employed to prepare samples of dinosterol for analysis. Collected algae samples can be centrifuged and then lyophilized. A Bligh and Dyer extraction can then be performed to isolate the major lipid classes. Lipid samples are often derivatized with bis(trimethylsilyl)trifluoroacetamide (BSTFA) for gas chromatography-mass spectrometry (GC-MS) analysis.
In biology, a pair bond is the strong affinity that develops in some species between a mating pair, often leading to the production and rearing of young and potentially a lifelong bond. Pair-bonding is a term coined in the 1940s that is frequently used in sociobiology and evolutionary biology circles. The term often implies either a lifelong socially monogamous relationship or a stage of mating interaction in socially monogamous species. It is sometimes used in reference to human relationships.
State institutions that were allowed to perform sterilizations on patients that seemed like the perfect candidate, was very common. Current research shows that Latinas were targets for sterilization at higher rates than white women. The disproportion among sterilization rates in the Latino community could not be quantified in its current time, but data from sterilization forms suggest that 88 percent of Californians with a Spanish last name were of Mexican origin and descent. The surnames of people in forms recommending institutionalized patients between 1920 and 1945 shows that Latino were more likely to be sterilized than non-Latino men and Latina women experienced sterilization at higher rates than non-Latina women. This data shows that there was an unfair application of the California law that allowed institutions to take health measures for other people on their behalf.
Sources: en.wikipedia.org
Chromatin immunoprecipitation (ChIP) is a method used to determine the location of DNA binding sites on the genome for a particular protein of interest. This technique gives a picture of the protein–DNA interactions that occur inside the nucleus of living cells or tissues. The in vivo nature of this method is in contrast to other approaches traditionally employed to answer the same questions. The principle underpinning this assay is that DNA-binding proteins (including transcription factors and histones) in living cells can be cross-linked to the DNA that they are binding. By using an antibody that is specific to a putative DNA binding protein, one can immunoprecipitate the protein–DNA complex out of cellular lysates. The crosslinking is often accomplished by applying formaldehyde to the cells (or tissue), although it is sometimes advantageous to use a more defined and consistent crosslinker such as dimethyl 3,3′-dithiobispropionimidate-2 HCl (DTBP). Following crosslinking, the cells are lysed and the DNA is broken into pieces 0.2–1.0 kb in length by sonication. At this point the immunoprecipitation is performed resulting in the purification of protein–DNA complexes. The purified protein–DNA complexes are then heated to reverse the formaldehyde cross-linking of the protein and DNA complexes, allowing the DNA to be separated from the proteins. The identity and quantity of the DNA fragments isolated can then be determined by polymerase chain reaction (PCR).
=== Ion pair extraction === It is possible by careful choice of counterion to extract a metal. For instance, if the nitrate concentration is high, it is possible to extract americium as an anionic nitrate complex if the mixture contains a lipophilic quaternary ammonium salt. An example that is more likely to be encountered by the 'average' chemist is the use of a phase transfer catalyst. This is a charged species that transfers another ion to the organic phase. The ion reacts and then forms another ion, which is then transferred back to the aqueous phase. For instance, the 31.1 kJ mol−1 is required to transfer an acetate anion into nitrobenzene, while the energy required to transfer a chloride anion from an aqueous phase to nitrobenzene is 43.8 kJ mol−1. Hence, if the aqueous phase in a reaction is a solution of sodium acetate while the organic phase is a nitrobenzene solution of benzyl chloride, then, when a phase transfer catalyst, the acetate anions can be transferred from the aqueous layer where they react with the benzyl chloride to form benzyl acetate and a chloride anion. The chloride anion is then transferred to the aqueous phase. The transfer energies of the anions contribute to that given out by the reaction. A 43.8 to 31.1 kJ mol−1 = 12.7 kJ mol−1 of additional energy is given out by the reaction when compared with energy if the reaction had been done in nitrobenzene using one equivalent weight of a tetraalkylammonium acetate.
== History == One of the earliest accounts of the tetrahedral intermediate came from Rainer Ludwig Claisen in 1887. In the reaction of benzyl benzoate with sodium methoxide, and methyl benzoate with sodium benzyloxide, he observed a white precipitate which under acidic conditions yields benzyl benzoate, methyl benzoate, methanol, and benzyl alcohol. He named the likely common intermediate “additionelle Verbindung.”
== Reactive dyes == The dyes used in this type of chromatography are inexpensive and generally available as they are from textile industries called reactive dye. It contains chromophores that are often attached to a triazine ring. In textile industries, reactive dyes are used to dye material like cotton which is cellulose. Commonly used reactive dyes for chromatography can be separated according to their color index name or functional group. Noted that each company has different trade names and slightly different formulas of the reactive dyes. Usually available commercially with sepharose as the supporting matrix in the form of packed columns.
Sources: en.wikipedia.org
The solid is kept cold, dry and dark, typically at minus twenty degrees Celsius, in a sealed container with desiccant. Dissolved material is kept refrigerated and used promptly. Freezing and thawing a solution repeatedly is avoided because it accelerates degradation.
Reversed-phase chromatography with ultraviolet detection gives a purity percentage, while mass spectrometry confirms identity. Amino acid analysis checks the residue composition. Buyers typically request a certificate of analysis showing these measurements for the specific lot.
It is not authorised as a medicine in the United States or the European Union. Material is sold there as a research chemical or cosmetic ingredient. Some related short peptides are registered drugs in Russia, which is a distinct national situation rather than a general approval.
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.