A practical reference on HPLC purity: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-11-26. Anything still debated is marked as such rather than presented as settled.
The compound is generally described as a synthetic analogue of a fragment isolated from a pineal gland extract. Researchers associated with the Saint Petersburg Institute of Bioregulation and Gerontology introduced it during the 1980s and 1990s while studying short peptides from animal tissue. The original extract, called epithalamin, is a heterogeneous mixture, whereas epitalon is a single defined sequence. That distinction matters because findings reported for the extract are not automatically findings about the pure tetrapeptide, and claims about broader biological effects remain a separate question from the chemical identity described here.
Residue composition is the property that most cleanly separates verified material from mislabelled samples. Alanine, glutamate, aspartate and glycine appear in that order from the N-terminus, and the two acidic residues sit in the middle of the chain. Because the peptide is short, it can be produced by solid-phase synthesis and characterised by mass spectrometry without ambiguity. Any reported sample whose measured mass departs substantially from 390 daltons is a different compound or a degraded mixture rather than epitalon.
Epitalon is a synthetic tetrapeptide whose four residues are alanine, glutamate, aspartate and glycine, commonly abbreviated AEDG. Its molecular formula is C14H22N4O9 and its monoisotopic mass is near 390.35 daltons. The peptide carries two acidic side chains, so it is neutral to negatively charged in most aqueous buffers. Published reference summaries usually list it under both spellings, epitalon and epithalon, and treat the two names as the same material.
The published literature is dominated by a small number of research groups, much of it in Russian-language journals, and independent replication outside those groups is limited. Studies are typically small, use cultured cells or rodent models, and report endpoints that differ between papers, which makes comparison difficult. Large randomised human trials have not appeared in the indexed literature. Questions about absorption, distribution and clearance are therefore still treated as open in reviews that mention the compound.
Epitalon is a synthetic tetrapeptide with the sequence alanine–glutamate–aspartate–glycine, commonly abbreviated AEDG. Its design traces to epithalamin, a peptide fraction prepared from bovine pineal gland extracts that researchers in Saint Petersburg began investigating in the 1970s. The compound has a molecular formula of C14H22N4O9 and a nominal molecular mass near 390 daltons. It holds no approved drug status in the United States or the European Union, and material sold under this name is generally offered as a research chemical rather than a finished pharmaceutical product.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C14H22N4O9 | Derived from the four constituent residues |
| Molecular mass | About 390.35 Da | Monoisotopic value, confirmed by mass spectrometry |
| Residue sequence | Ala-Glu-Asp-Gly | Read from the N-terminus to the C-terminus |
| Common synonyms | Epithalon; AEDG | Both forms appear in reference catalogues |
| Net charge near neutral pH | Negative | Two acidic side chains give a low isoelectric point |
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.
=== Use in BLAST === BLOSUM matrices are also used as a scoring matrix when comparing DNA sequences or protein sequences to judge the quality of the alignment. This form of scoring system is utilized by a wide range of alignment software including BLAST.
=== Caloric value and labeling === Nutritional labeling of erythritol in food products varies from country to country. Some places, such as Japan and the European Union (EU), label it as zero-calorie. Under Food and Drug Administration (FDA) labeling requirements in the United States, erythritol has a caloric value of zero.
TRH is also produced in many hypothalamic neurons not associated with the pituitary, as well as multiple other CNS regions (including the spinal cord, brainstem, thalamus, amygdala, and hippocampus), indicating various non-neuroendocrine functions. TRH is additionally produced in multiple endocrine and non-endocrine tissues outside the CNS, including the anterior pituitary, parafollicular cells of the thyroid glands, medulla of the adrenal gland, islet cells of the pancreas, Leydig cells of the testis, epididymis, prostate, GI tract, spleen, lung, ovary, retina, and hair follicles.
To enforce the amendment, Congress passed the National Prohibition Act, also known as the Volstead Act. The Prohibition Bureau Narcotics Division, which enforced the Harrison Act, was overseen by Levi G. Nutt, the 1st narcotics commissioner of the United States. By the 1930s, the policy was seen as a failure: production and consumption of alcohol persisted, organized crime flourished in the alcohol black market, and tax revenue, particularly needed after the start of the Great Depression in 1929, was lost. Prohibition was repealed by passage of the 21st Amendment in 1933, with President Franklin D. Roosevelt (1933–1945) asking Americans not to abuse "this return to personal freedom." In 1922, the Narcotic Drugs Import and Export Act broadened federal regulation of opiates and coca products by prohibiting import and export for non-medical use, and established the Federal Narcotics Control Board (FNCB) to administrate.
==== Multi-Collector Inductively Coupled Plasma-Mass Spectrometry ==== This is a frequently used technique in nuclear forensics. In this technique a purified sample is nebulized in a spray chamber and then aspirated into a plasma. The high temperature of the plasma leads to sample dissociation and high efficiency of ionization of the analyte. The ions then enter the mass spectrometer where they are discriminated based on mass based on a double focusing system. Ions of various masses are detected simultaneously by a bank of detectors similar to those used in the thermal ionization mass spec. MC-ICP-MS has a more rapid analysis because it does not require lengthy filament preparation. For high quality, however, there is a requirement for extensive sample cleanup. Argon plasma is also less stable and requires relatively expensive equipment as well as skilled operators.
Sources: en.wikipedia.org
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=== Sex === This is especially concerning considering the epidemiology of opioid affliction among white women, who are at a greater risk because they receive more prescription medications than men. According to the NIH (2018), "The opioid epidemic is increasingly young, white, and female" with 1.2 million women being diagnosed with an opioid use disorder compared to 0.9 million men in 2015.
=== Vitamin levels === Studies conducted so far suggest that subjects with GS may have lower levels of vitamin D and folic acid than control subjects, having these levels inversely correlated with bilirubin levels. It may be that GS may impair the metabolism or absorption of these vitamins, or that these vitamins may affect the expression or activity of the UGT1A1 enzyme that is responsible for bilirubin conjugation. However, these studies had limitations, such as the small sample size, the lack of a standardized definition of GS, the possible confounding factors of diet, lifestyle, and medication use, and the cross-sectional and observational design that does not allow for causal inference.
=== Standard data format for mass spectrometry imaging datasets === The imzML was proposed to exchange data in a standardized XML file based on the mzML format. Several imaging MS software tools support it. The advantage of this format is the flexibility to exchange data between different instruments and data analysis software.
Sources: en.wikipedia.org
When amphetamine enters a neuron and interacts with VMAT2, the transporter reverses its direction of transport, thereby releasing stored monoamines inside synaptic vesicles back into the neuron's intracellular fluid. Meanwhile, when amphetamine activates TAAR1, the receptor causes the neuron's cell membrane-bound monoamine transporters (i.e., the dopamine transporter, norepinephrine transporter, or serotonin transporter) to either stop transporting monoamines altogether (via transporter internalization) or transport monoamines out of the neuron; in other words, the reversed membrane transporter will push dopamine, norepinephrine, and serotonin out of the neuron's intracellular fluid and into the synaptic cleft. In summary, by interacting with both VMAT2 and TAAR1, amphetamine releases neurotransmitters from synaptic vesicles (the effect from VMAT2) into the intracellular fluid where they subsequently exit the neuron through the membrane-bound, reversed monoamine transporters (the effect from TAAR1).
== Applications == The efficacy of hydrogel dressings has been assessed on various wound types. There is some evidence to suggest that hydrogels are effective dressings for chronic wounds including pressure ulcers, diabetic ulcers, and venous ulcers although the results are uncertain. Hydrogels have been shown to accelerate healing in partial and full thickness burn wounds of varying size. Other studies have shown that hydrogel dressings accelerate healing in radioactive skin injuries and dog bite wounds. Hydrogel dressings decrease the healing time of traumatic skin injuries by an average 5.28 days and reduce the pain reported by patients.
== Function == Adenine is one of the two purine nucleobases (the other being guanine) used in forming nucleotides of the nucleic acids. In DNA, adenine binds to thymine via two hydrogen bonds to assist in stabilizing the nucleic acid structures. In RNA, which is used for protein synthesis, adenine binds to uracil.
Sources: en.wikipedia.org
It is a four-amino-acid peptide built from alanine, glutamate, aspartate and glycine in that order. Its formula is C14H22N4O9, and it is made by chemical synthesis rather than extracted from tissue. The synthetic peptide is a single defined molecule, unlike the pineal extracts it is often compared with.
No. The two spellings refer to the same tetrapeptide, and the difference reflects transliteration from Russian. Laboratories and catalogues use both forms interchangeably. The material is also indexed as AEDG, taken from the one-letter codes of its residues.
Epithalamin is a mixed preparation derived from animal pineal tissue and contains many peptides. Epitalon is one synthetic sequence chosen for study from that broader mixture. Statements about one do not transfer directly to the other.
No. Epithalamin is a heterogeneous peptide fraction obtained from pineal gland extract and contains many components. Epitalon is a single synthetic tetrapeptide with the sequence Ala-Glu-Asp-Gly. Researchers synthesised the shorter peptide while attempting to identify active sequences within the extract.