The short version of Deamidation fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-09-21. Anything still debated is marked as such rather than presented as settled.
Reversed-phase high-performance liquid chromatography is the standard approach for assessing purity, usually with ultraviolet detection near 214 nm, where the peptide bond absorbs. Mass spectrometry, most often with electrospray ionization, confirms the molecular mass and helps reveal truncation or deletion byproducts. Amino acid analysis can verify composition, and counterion content is sometimes measured because peptides purified with trifluoroacetic acid retain variable amounts of that salt. Purity figures reported without a stated method and detection wavelength are difficult to interpret.
Material sold for research use varies widely in documented quality. A useful verification package includes a certificate of analysis that states peptide content rather than only net weight, the chromatographic method and column used, and a mass spectrum consistent with the expected mass. Independent testing by a third-party laboratory is occasionally reported. Statements of identity resting only on a supplier label provide little assurance, and the gap between nominal mass and actual peptide content can be substantial once counterions and residual water are counted.
Peptides of this size are generally stable as dry solids but degrade in solution over time. The principal routes are hydrolysis of the peptide backbone and oxidation, with hydrolysis favoured by elevated temperature and extreme pH. Aqueous solutions held at room temperature can show measurable loss of purity within days, while frozen aliquots are considerably more durable. Because the sequence contains neither cysteine nor methionine, oxidation is less of a concern than for many other peptides, but pH control during handling still matters.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilized solid |
| Solubility | Freely soluble in water | Also dissolves in polar organic solvents |
| Typical storage temperature | −20 °C or below | Sealed, desiccated, protected from light |
| Primary purity assay | Reversed-phase HPLC | Ultraviolet detection near 214 nm |
| Identity confirmation | Mass spectrometry | Electrospray ionization commonly used |
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.
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.
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.
Verification of a sample usually begins with reversed-phase high-performance liquid chromatography, which resolves the peptide from truncated sequences and other impurities and expresses purity as a percentage of total peak area. Mass spectrometry by electrospray ionisation or matrix-assisted laser desorption supplies an independent check, because the measured mass can be compared against the theoretical value for AEDG. Amino acid analysis or tandem mass spectrometry sequencing can confirm residue order. Each of these methods answers a different question: a purity figure does not establish identity, and an identity match does not establish how much of the material is intact peptide.
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.
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.
Gastrointestinal cancer may occur at any point in the gastrointestinal tract, and includes mouth cancer, tongue cancer, oesophageal cancer, stomach cancer, and colorectal cancer. One possible factor in the etiology of gastrointestinal cancers is excessive exposure of the digestive organs to bile acids. Inflammatory conditions. Ileitis is an inflammation of the ileum, colitis is an inflammation of the large intestine. Intestinal necrotizing arteriolitis is an inflammation of the arteries in the intestines, causing widespread severe acute lesions. Appendicitis is inflammation of the appendix located at the caecum. This is a potentially fatal condition if left untreated; most cases of appendicitis require surgical intervention. Diverticular disease is a condition that is very common in older people in industrialized countries. It usually affects the large intestine but has been known to affect the small intestine as well. Diverticulosis occurs when pouches form on the intestinal wall. Once the pouches become inflamed it is known as diverticulitis. Inflammatory bowel disease is an inflammatory condition affecting the bowel walls, and includes the subtypes Crohn's disease and ulcerative colitis. While Crohn's can affect the entire gastrointestinal tract, ulcerative colitis is limited to the large intestine. Crohn's disease is widely regarded as an autoimmune disease. Although ulcerative colitis is often treated as though it were an autoimmune disease, there is no consensus that it actually is such.
Russell's viper (Daboia russelii) produces one of the most excruciatingly painful bites of all venomous snakes. Internal bleeding is common. Bruising, blistering and necrosis may appear relatively quickly as well. The Russell's viper, although usually slow and sluggish and shunning humans in general, may resort to striking at a lightning speed when provoked beyond a certain limit. This species is responsible for more human fatalities in India than any other snake species, causing an estimated 25,000 fatalities annually. The LD50 in mice is 0.133 mg/kg intravenous, 0.40 mg/kg intraperitoneal, and about 0.75 mg/kg subcutaneous. For most humans, a lethal dose is approximately 40–70 mg. The quantity of venom produced by individual specimens is considerable, with reported venom yields for adult specimens ranging from 130–250 mg to 150–250 mg to 21–268 mg. For 13 juveniles with an average length of 79 cm, the average venom yield was 8–79 mg (mean 45 mg).
Penn Station does not have a unified design or floor plan but rather is divided into separate Amtrak, LIRR and NJ Transit concourses with each concourse maintained and styled differently by its respective operator. The Amtrak and NJ Transit concourses are located on the first level below the street level while the Long Island Rail Road concourse is two levels below street level. The layout has been called a "confusing, multilevel maze of corridors," even prompting Amtrak at one point to release an app to assist commuters in navigating the station. Platform widths vary, with eight of the 11 platforms in the range of 19–20 feet wide. Platform 6 is the narrowest, at 17 feet, while Platform 1 is slightly wider, at 22 feet. Platform 10 is the widest platform, used exclusively by LIRR and nominally 38 feet wide. The main concourse, which was principally used by Amtrak until the opening of the Moynihan Train Hall in 2021, is at the west end of the block directly beneath Madison Square Garden and now used principally by NJ Transit. It was created out of the original station's waiting rooms and main concourse, though few remnants of the original still exist in the space. It was renovated in the early 2000s in anticipation of Acela service and includes an enclosed waiting area for ticketed passengers with seats, outlets and Wi-Fi.
== Structure and bonds == Conjugated proteins always have a prosthetic group that is highly associated with the polypeptide chain. Association can occur either through covalent bonding or strong noncovalent interactions like hydrogen bonding, ionic bonding, or coordination bonding. Depending on whether the prosthetic group is a carbohydrate or phosphate, covalent bonds would involve the formation of either glycoside linkage between the carbohydrate and amino acids or ester linkage between the phosphate residue and the protein.
Sources: en.wikipedia.org
== Etymology == The word Portugal derives from Latin Portus Cale, a Roman name meaning 'port of Cale', itself the origin of the name of the Portuguese city of Porto, while Cale was a town on the Douro. There is no consensus on the etymology of Cale. It could derive from the pre-Indo-European word Kala, meaning 'shelter' or 'refuge', passed into the Celtic language in the form Cale, with the meaning of 'land' or 'mountain'. The ethnonym Calaico/a then came from the Gallaeci, Celtic peoples of northwestern Iberia, and came to mean 'one of the land' or 'one of the place. During the Middle Ages, the region around Portus Cale became known by the Visigoths as Portucale and by the Suebi as Parochiale. The name Portucale evolved into Portugale; by the 11th and 12th centuries Portugal referred to the region between the Douro and Minho rivers.
==== Removal of the spleen ==== The spleen is the organ which removes damaged or misshapen red blood cells from the circulation. In thalassemia, this can lead to the spleen becoming enlarged, a condition known as splenomegaly. Slight enlargement of the spleen is not a problem, however if it becomes extreme then surgical removal of the spleen (splenectomy) may be recommended.
Taking a break from training to allow time for recovery. Reducing volume and/or intensity of training. Suitable periodization of training. Splitting the training program so that different sets of muscles are worked on different days. Increase sleep time. Deep-tissue or sports massage of the affected muscles. Self-massage or rub down of the affected muscles. Short sprints with long resting time once the athlete is able to continue with light training.
Sources: en.wikipedia.org
Simple compounds that are converted into other compounds with the assistance of cofactors. For example, the synthesis of phospholipids requires acetyl CoA, while the synthesis of another membrane component, sphingolipids, requires NADH and FADH for the formation the sphingosine backbone. The general equation for these examples is:
=== Exercise === Exercise has been shown to improve insulin sensitivity in humans with metabolic syndrome. Increased exercise is therefore recommended in horses with EMS, assuming laminitis does not restrict activity levels. Current recommendations include 2–3 sessions a week, of 20–30 minutes of work, with gradual increase in duration and intensity.
=== Complications === Cats typically die due to complications associated with sepsis, dehydration, and disseminated intravascular coagulopathy (DIC). Leukocytopenia predisposes patients to secondary infections, especially bacterial and fungal, though secondary viral infections also occur. It has been stated that cats with FPLV may be at risk for endocarditis or cardiomyopathy (since CPV-2 is a well-known cause of viral myocarditis in young puppies), but a 2017 retrospective study concluded that "Feline Panleukopenia Virus Is Not Associated With Myocarditis or Endomyocardial Restrictive Cardiomyopathy in Cats".
Sources: en.wikipedia.org
The powder is normally kept at −20 °C or below in a sealed, moisture-protected container. Letting the vial reach room temperature before opening helps prevent condensation on the contents.
Reversed-phase HPLC with ultraviolet detection is the usual approach, often paired with mass spectrometry. Together the two methods address both chromatographic purity and molecular identity.
Differences arise from the analytical method, the detection wavelength, and whether the number refers to the peptide or to total powder mass. Counterion and water content can lower the actual peptide fraction considerably.
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.