A practical reference on aspartimide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-03-28 and is reviewed periodically as new material appears.
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.
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.
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.
The PLA is a component of the armed forces of China, which also includes the PAP, the reserves, and the militia. The armed forces are controlled by the CCP under the doctrine of "the Party commands the gun". The PLA and the PAP have the largest delegation in the National People's Congress (NPC), which are elected by servicemember election committees of top-level military subdivisions, including the PLA's theater commands and service branches. At the 14th National People's Congress; the joint delegation has 281 deputies—over 9% of the total—all of whom are CCP members.
In biology and biochemistry, the active site is the region of an enzyme where substrate molecules bind and undergo a chemical reaction. The active site consists of amino acid residues that form temporary bonds with the substrate, the binding site, and residues that catalyse a reaction of that substrate, the catalytic site. Although the active site occupies only ~10–20% of the volume of an enzyme, it is the most important part as it directly catalyzes the chemical reaction. It usually consists of three to four amino acids, while other amino acids within the protein are required to maintain the tertiary structure of the enzymes. Each active site is evolved to be optimised to bind a particular substrate and catalyse a particular reaction, resulting in high specificity. This specificity is determined by the arrangement of amino acids within the active site and the structure of the substrates. Sometimes enzymes also need to bind with some cofactors to fulfil their function. The active site is usually a groove or pocket of the enzyme which can be located in a deep tunnel within the enzyme, or between the interfaces of multimeric enzymes. An active site can catalyse a reaction repeatedly as residues are not altered at the end of the reaction (they may change during the reaction, but are regenerated by the end). This process is achieved by lowering the activation energy of the reaction, so more substrates have enough energy to undergo reaction.
Simple compounds which are converted into other compounds, usually as part of a multiple step reaction pathway. Two examples of this type of reaction occur during the formation of nucleic acids and the charging of tRNA prior to translation. For some of these steps, chemical energy is required:
Sources: en.wikipedia.org
Atherosclerosis Hyperglycemia from consumption of excess sugars (includes juices, sauces, alcohol) & processed Carbohydrates. Neoplasm Overeating Inactivity & lack of muscle strength. See Physical inactivity and Physical activity. Pancreatic cancer Trans fats
== Genetically encoding the aldehyde tag == The formylglycine tag or aldehyde tag is a convenient 6- or 13-amino acids long tag fused to a protein of interest. The 6-mer tag represents the small core consensus sequence and the 13-mer tag the longer full motif. The experiments on the genetically encoded aldehyde tag by clearly showed the high conversion efficiency with only the core consensus sequence present. Four proteins were produced recombinantly in E.coli with an 86% efficiency of for the full-length motif and >90% efficiency for the 6-mer determined by mass spectrometry. The size of the sequence is analogous to the commonly used 6x His-Tag and has the advantage that it can also be genetically encoded. The sequence is recognized in the ER solely depending on primary sequence and subsequently targeted by FGE. Notably, in the setup of recombinant expression proteins in E. coli a coexpression of exogenous FGE aids full conversion, although E. coli has endogenous FGE-activity. The introduction of an aldehyde tag has a workflow that consists of three segments: A the expression of the fusion protein, that carries the peptide tag derived from the sulfatase motif, B the enzymatic conversion of Cys to f(Gly) and C the bioorthogonal probing with hydrazides or alkoxy amines (Fig. 1).
=== Gastrointestinal === Diarrhoea that is characteristic of coeliac disease is chronic, sometimes pale, of large volume, and abnormally foul in odour. Other symptoms of coeliac disease include abdominal pain, cramping, bloating with abdominal distension, and mouth ulcers. As the bowels become more damaged, lactose intolerance can develop.
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histone Any of a class of highly alkaline proteins responsible for packaging nuclear DNA into structural units called nucleosomes in eukaryotic cells. Histones are the chief protein components of chromatin, where they associate into eight-membered complexes which act as "spools" around which the linear DNA molecule winds. They play a major role in gene regulation and expression.
In 1897, portions of an octopus, said to have been more gigantic than any ever before seen, were washed up on the beach at St. Augustine. Prof. Verrill, of Yale University, who examined the remains, which alone reputedly weighed over six tons, calculated that the living creature had a girth of 25 feet and tentacles 72 feet in length! He learned that a sample of the integument was preserved in the Smithsonian Institution, and persuaded the curators to send a portion of the sample to his colleague, Dr. Joseph F. Gennaro Jr., a cell biologist at the University of Florida. Gennaro compared the connective tissue of the St. Augustine carcass to control specimens from known octopus and squid species. He published his findings in the March 1971 issue of Natural History:
Within 4 hours, the main administrative and communication nodes in the capital were brought under control and the political leaders of the coup moved to the War Ministry. At 6:25 a.m., Kimon Georgiev read a short Proclamation to the Bulgarian people over the radio and announced the composition of the new government, approved a short time later by decree of the regents Prince Kiril and Nikola Mihov.
Bevan later appears on television defending the government while acknowledging her own role in supporting Tender. After Henry is arrested and agrees to testify, he contacts Bevan about possible Russian intelligence involvement in Tender’s operations; she attempts to escalate the matter to the prime minister but is warned by the chief of staff against pursuing it further, due to the potential diplomatic ramifications and the credibility of Bevan's sources.
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.