aspartimide raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-06-17 and is reviewed periodically as new material appears.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Analytical method | Reversed-phase HPLC | Purity determination, typically 214 nm |
| Mass confirmation | ESI or MALDI mass spectrometry | Compared with mass near 390 Da |
| Common synonyms | Epitalon, epithalon, AEDG | Naming differs between suppliers |
| Storage temperature | −20 °C or lower | Lyophilised powder, kept desiccated |
| Solution stability | Limited in neutral aqueous buffer | Aspartimide and hydrolysis pathways |
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.
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.
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.
Portal was singled out for praise by reviewers. Official Xbox Magazine admired its unique puzzle gameplay mechanics, stating that it was the first major advance in puzzle gaming "since Russians started dropping blocks", referring to Tetris. The Escapist's Ben "Yahtzee" Croshaw stated in his Zero Punctuation review that he could not think of any criticism for Portal, saying that it had "some of the funniest pitch-black humor [he had] ever heard in a game" and concluded that it is "absolutely sublime from start to finish." The PlayStation 3 version's critical review scores suffered because of the technical issues first uncovered by 1UP.com. While discussing the retail version on a podcast, 1UP.com staff members agreed that a significant number of the frame rate problems had been resolved, but not all of them. They concluded that the PlayStation 3 version was not quite as smooth as the Xbox 360 version and recommended that "if you own both [consoles], you should do the 360" version. Kotaku's Michael McWhertor echoed that recommendation, though stated that those who only have a PlayStation 3 should still consider The Orange Box. While frame rate issues were the main complaint, the PlayStation 3 version was also criticized for unreliable voice chat and excessive network delay or lag in Team Fortress 2, as well as long load times generally. It was, however, praised for featuring anti-aliasing and a quick-save feature, neither of which were present in the Xbox 360 version (but were present in the PC version).
== Genes == Most research that has been conducted on CLE peptide signaling has been conducted with Arabidopsis, since this genome contains 32 members of the CLE gene family. CLV3, which belongs to the CLE family of genes, is found within one or more tissues of Arabidopsis. All 32 members of the CLE family share two characteristics that include: encoding of a small protein with a putative secretion signal at their N- termini and contain a conserved CLE motif at or near their C-termini. The 32 members of the CLE gene family originated from mutations of the original gene.
Within the international relations literature, international organizations facilitate cooperation between states by reducing transaction costs, providing information, making commitments more credible, establishing focal points for coordination, facilitating the principle of reciprocity, extending the shadow of the future, and enabling interlinkages of issues, which raises the cost of noncompliance. States may comply with the decisions of international organizations, even when they do not want to, for rational cost-benefit calculations (to reap concrete rewards of future cooperation and avoid punishment) and normative reasons (social learning and socialization). International organizations vary in terms of: inclusive or exclusive membership; broad or narrow scope; equal or unequal control by members; precision and flexibility of rules; hard or soft obligations; and delegation of power to the international organization. Other examples of international organizations include the UN General Assembly, the World Trade Organization, the African Development Bank, the UN Economic and Social Council, the UN Security Council, the Asian Development Bank, the International Bank for Reconstruction and Development, the International Monetary Fund, the International Finance Corporation, the Inter-American Development Bank, and the United Nations Environment Programme.
== Lifecycle == Bowfin spawn in the spring or early summer, typically between April and June, more commonly at night in abundantly vegetated, clear, shallow water in weed beds over sand bars and also under stumps, logs, and bushes. Optimum temperatures for nesting and spawning range between 16 and 19 °C (61 and 66 °F). The males construct circular nests in fibrous root mats, clearing away leaves and stems. Depending on the density of surrounding vegetation, a tunnel-like entrance may be at one side. The diameter of the nests commonly range between 39 and 91 cm (15 and 36 in), at a water depth of 61–92 cm (24–36 in). During spawning season, the fins and underside of male bowfin often change in color to a bright lime green. The courtship/spawning sequence lasts 1-3 hours and can repeat up to five times. Courtship begins when a female approaches the nest. The ritual consists of intermittent nose bites, nudges, and chasing behavior by the male until the female becomes receptive, when the pair lie side by side in the nest. She deposits her eggs, while he shakes his fins in a vibratory movement, and releases his milt for fertilization to occur. A male often has eggs from more than one female in his nest, and a single female often spawns in several nests. Females vacate the nest after spawning, leaving the male behind to protect the eggs during the 8-10 days of incubation. A nest may contain 2,000 to 5,000 eggs, possibly more. Fecundity is usually related to size of the fish, so the roe of a large gravid female may contain over 55,000 eggs.
Amyloids are formed of long unbranched fibers that are characterized by an extended β-sheet secondary structure in which individual β strands (β-strands) (coloured arrows in the adjacent figure) are arranged in an orientation perpendicular to the long axis of the fiber. Such a structure is known as cross-β structure. Each individual fiber may be 7–13 nanometres in width and a few micrometres in length. The main hallmarks recognised by different disciplines to classify protein aggregates as amyloid is the presence of a fibrillar morphology with the expected diameter, detected using transmission electron microscopy (TEM) or atomic force microscopy (AFM), the presence of a cross-β secondary structure, determined with circular dichroism, FTIR, solid-state nuclear magnetic resonance (ssNMR), X-ray crystallography, or X-ray fiber diffraction (often considered the "gold-standard" test to see whether a structure contains cross-β fibres), and an ability to stain with specific dyes, such as Congo red, thioflavin T or thioflavin S. The term "cross-β" was based on the observation of two sets of diffraction lines, one longitudinal and one transverse, that form a characteristic "cross" pattern. There are two characteristic scattering diffraction signals produced at 4.7 and 10 Å (0.47 nm and 1.0 nm), corresponding to the interstrand and stacking distances in β sheets. The "stacks" of β sheet are short and traverse the breadth of the amyloid fibril; the length of the amyloid fibril is built by aligned β-strands. The cross-β pattern is considered a diagnostic hallmark of amyloid structure.
Sources: en.wikipedia.org
A tendon is a tough, flexible band of fibrous connective tissue that connects muscles to bones. The extra-cellular connective tissue between muscle fibers binds to tendons at the distal and proximal ends, and the tendon binds to the periosteum of individual bones at the muscle's origin and insertion. As muscles contract, tendons transmit the forces to the relatively rigid bones, pulling on them and causing movement. Tendons can stretch substantially, allowing them to function as springs during movement. Cartilage is a resilient and smooth type of connective tissue that covers and protects the ends of long bones, and forms a structural component of many body parts including the rib cage, the neck and the bronchial tubes, and the intervertebral discs. It is classified into three types — elastic cartilage, hyaline cartilage, and fibrocartilage. Joints, also known as articulations, are structures that connect individual bones and may allow bones to move against each other to cause movement. Joints can be classified by structure and by function. Structurally, synovial joints are joints that are not directly joined, which are lubricated by a solution called synovial fluid; fibrous, bony, and cartilaginous joints are characterised by the presence of their respective connective tissues. There are three functional divisions of joints: Diarthroses, which allow extensive mobility between two or more articular heads. Amphiarthroses, which allow some movement. False joints or synarthroses, which allow little or no movement and are predominantly fibrous.
=== Prothrombin time ratio === The prothrombin time ratio is the ratio of a subject's measured prothrombin time (in seconds) to the normal laboratory reference PT. The PT ratio varies depending on the specific reagents used, and has been replaced by the INR.
== See also == Russell 3000 Index – U.S. all-cap stock market index Russell 1000 Index – U.S. large-cap stock market index S&P 600 – American small-cap stock market index List of largest daily changes in the Russell 2000
=== Role in melanoma metastasis === Heavily pigmented melanoma cells have a Young's modulus of about 4.93 kPa, compared to non-pigmented cells, with a value of 0.98 kPa. The elasticity of melanoma cells is crucial to metastasis and growth; non-pigmented tumors were larger than pigmented tumors, and spread far more easily. Pigmented and non-pigmented cells are both present in melanoma tumors, so that they can both be drug-resistant and metastatic.
. . .the earlier investigations that seem so simple and obvious in the light of our present knowledge, so easy with the equipment now available, were anything but simple and obvious the first time they were done. In 1942, after four decades of service, Lore Rogers, age 67 retired from the United States Department of Agriculture after a productive career with 86 papers published in scientific journals and U. S. Department of Agriculture bulletins.
Sources: en.wikipedia.org
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.
Neutral and slightly basic aqueous conditions promote aspartimide formation at the aspartate-glycine step, often followed by deamidation. Elevated temperature and repeated freeze-thaw cycles accelerate the loss. Acidic solutions and dry lyophilised powder are comparatively stable over short periods.
No monograph exists in the United States Pharmacopeia or the European Pharmacopoeia, and no widely distributed certified reference standard is available. Purity and identity therefore rest on supplier methods that are not harmonised. This absence is the main reason reported purities are difficult to compare between sources.
It is a four-amino-acid peptide with the sequence alanine-glutamate-aspartate-glycine. The chain is unmodified and contains only standard proteinogenic residues, which makes it straightforward to produce by solid-phase synthesis and to characterise by standard peptide methods.