If you have been reading about mass spectrometry and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-03-03. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Amino acid sequence | Ala-Glu-Asp-Gly | Linear tetrapeptide, also written AEDG |
| Molecular mass | About 390.35 g/mol | Value calculated from the sequence |
| Appearance | White to off-white powder | Lyophilised material forms a loose cake |
| Solubility | Freely soluble in water | Also dissolves in isotonic saline |
| Storage | -20 °C, desiccated | Aliquot solutions to avoid freeze–thaw cycling |
The peptide is a synthetic analogue of epithalamin, a preparation extracted from bovine pineal glands. Investigators sought a short, chemically defined molecule that would reproduce some of the endocrine and gerontological observations attributed to the glandular extract. Proposed mechanisms centre on induction of telomerase activity, an effect reported in cultured human somatic cells in the early 2000s, together with influences on melatonin secretion and neuroendocrine regulation. Those mechanisms remain incompletely characterised, and the reported telomerase response has not been consistently reproduced by independent groups working in comparable systems.
Published work on this compound consists mainly of in vitro experiments, animal studies, and small clinical investigations, a substantial share of which appeared in Russian-language journals. Sample sizes are generally small, control conditions differ between studies, and several endpoints rely on markers whose clinical meaning is itself debated. Reviews of the longevity field treat the peptide as an early example of telomerase-directed research rather than an established intervention. Regulatory treatment varies by country: some jurisdictions place it under prescription controls, others treat it as a laboratory material, and importation may be restricted regardless of local status.
Epitalon is a synthetic tetrapeptide whose sequence is alanine–glutamate–aspartate–glycine, commonly abbreviated AEDG. It was developed in Russia during the 1980s and 1990s by investigators associated with the St. Petersburg Institute of Bioregulation and Gerontology, who studied short peptides as regulators of gene expression and tissue function. The alternative spelling epithalon appears interchangeably in the literature, and the two names refer to the same molecule. Outside Russia it is encountered chiefly as a research chemical rather than a licensed medicine, and it holds no approval from the United States Food and Drug Administration or the European Medicines Agency.
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.
=== External proton gradient model === Biochemist Nick Lane has proposed the following hypothesis. Deep-sea hydrothermal vents, emitting hot acidic or alkaline water, would have created external proton gradients. These provided energy that primordial organisms could have exploited. To keep the flows separate, such an organism could have wedged itself in the rock of the hydrothermal vent, exposed to the hydrothermal flow on one side and the more alkaline water on the other. As long as the organism's membrane (or passive ion channels within it) is permeable to protons, the mechanism can function without ion pumps. Such a proto-organism could then have evolved further mechanisms such as ion pumps and ATP synthase.
==== Idiopathic calcinosis cutis ==== Skin calcification that is not linked to a systemic illness or an underlying tissue injury is referred to as idiopathic calcification. Most often, the calcification is restricted to a single general location, yet there has been one case of calcinosis cutis that is exceptionally broad.
The carnitine shuttle is a biochemical reaction used to transport long chain fatty acids (LCFAs) from the cytosol into the matrix of the mitochondria so that they may be metabolized. While some fatty acids can, long chain fatty acids cannot pass through the mitochondrial membrane. However, carnitine (specifically its stereoisomer l-carnitine) can. The shuttle utilizes this to its advantage by attaching the LCFAs to carnitine. This new acyl-carnitine can pass through the membrane, after which it is split, with the newly separated carnitine being sent back out to shuttle more LCFAs, and the newly separated LCFAs undergoing beta oxidation to release their energy. The carnitine shuttle is an example of an antiporter system, and is a part of the broader class of metabolic reactions that constitute lipid metabolism. It is a highly conserved system found primarily in animals/some eukaryotes, although bacteria and plants still use carnitine for other things such as being an osmoprotectant, or being and electron acceptor in the electron transport chain. The shuttle system is implicated in many metabolic disorders, in the form of deficiencies of the enzymes in the system.
This results in intense radiolabeling of tissues with high glucose uptake, such as the normal brain, liver, kidneys, and most cancers, which have a higher glucose uptake than most normal tissue due to the Warburg effect. As a result, FDG-PET can be used for diagnosis, staging, and monitoring treatment of cancers, particularly in Hodgkin lymphoma, non-Hodgkin lymphoma, and lung cancer. A 2020 review of research on the use of PET for Hodgkin lymphoma found evidence that negative findings in interim PET scans are linked to higher overall survival and progression-free survival; however, the certainty of the available evidence was moderate for survival, and very low for progression-free survival. A few other isotopes and radiotracers are slowly being introduced into oncology for specific purposes. For example, 11C-labelled metomidate (11C-metomidate) has been used to detect tumors of adrenocortical origin. Also, fluorodopa (FDOPA) PET/CT (also called F-18-DOPA PET/CT) has proven to be a more sensitive alternative to finding and also localizing pheochromocytoma than the iobenguane (MIBG) scan. For prostate cancer, there is growing interest in using a PET scan with radionuclides delivered via prostate-specific membrane antigen (PSMA) targeting ligand, a strategy which allows imaging the primary tumor and surrounding metastases in one scan. The combination is referred to as a PSMA scan.
As Richardson developed the ribbon diagram to illustrate her findings over the course of her taxonomic research, her iconic images first appeared in the review journal Advances in Protein Chemistry in an article titled "The anatomy and taxonomy of protein structure" 1981, an early hallmark publication in structural bioinformatics. The diagrams have since become a standard way of visualizing protein structure, specifically depicting beta-sheet topology and connections between amino acid sequences, or peptides, that make up proteins. The protein folding process involves four levels: primary structures, secondary structures, tertiary structures, and quaternary structures. Secondary structures result from hydrogen bond interactions between adjacent amino acids sequences to form alpha helices or beta-sheets. Tertiary structures are a higher order of protein folding that depict the conformation of and connectivity between alpha-helices and beta-sheets in 3D. Richardson's ribbon diagrams illustrate beta-sheet topology and connectivity in higher-order protein structures. She formalized general rules about beta-sheets linkage via "hairpin" connections or "crossover" connections. In a hairpin connection a peptide backbone stems out of and loops around to return to the same beta-sheet end from which it left. A crossover connection involves the peptide backbone extending out of one beta-sheet and looping around to enter another beta-sheet on the opposite end of the protein.
Sources: en.wikipedia.org
== Manufacturing == Although pseudoephedrine occurs naturally as an alkaloid in certain plant species (for example, as a constituent of extracts from the Ephedra species, also known as ma huang, in which it occurs together with other isomers of ephedrine), the majority of pseudoephedrine produced for commercial use is derived from yeast fermentation of dextrose in the presence of benzaldehyde. In this process, specialized strains of yeast (typically a variety of Candida utilis or Saccharomyces cerevisiae) are added to large vats containing water, dextrose and the enzyme pyruvate decarboxylase (such as found in beets and other plants). After the yeast has begun fermenting the dextrose, the benzaldehyde is added to the vats, and in this environment, the yeast converts the ingredients to the precursor l-phenylacetylcarbinol (L-PAC). L-PAC is then chemically converted to pseudoephedrine via reductive amination. The bulk of pseudoephedrine is produced by commercial pharmaceutical manufacturers in India and China, where economic and industrial conditions favor its mass production for export.
The cause of the 2006 death of Alexander Litvinenko, a former Russian FSB agent who had defected to the United Kingdom in 2001, was identified to be poisoning with a lethal dose of 210Po; it was subsequently determined that the 210Po had probably been deliberately administered to him by two Russian ex-security agents, Andrey Lugovoy and Dmitry Kovtun. As such, Litvinenko's death was the first (and, to date, only) confirmed instance in which polonium's extreme toxicity has been used with malicious intent. In 2011, an allegation surfaced that the death of Palestinian leader Yasser Arafat, who died on 11 November 2004 of uncertain causes, also resulted from deliberate polonium poisoning, and in July 2012, concentrations of 210Po many times more than normal were detected in Arafat's clothes and personal belongings by the Institut de Radiophysique in Lausanne, Switzerland. Even though Arafat's symptoms were acute gastroenteritis with diarrhoea and vomiting, the institute's spokesman said that despite the tests the symptoms described in Arafat's medical reports were not consistent with 210Po poisoning, and conclusions could not be drawn. In 2013 the team found levels of polonium in Arafat's ribs and pelvis 18 to 36 times the average, even though by this point in time the amount had diminished by a factor of 2 million. Forensic scientist Dave Barclay stated, "In my opinion, it is absolutely certain that the cause of his illness was polonium poisoning. ...
== Side effects == Common or clinically important adverse effects of phenelzine include orthostatic hypotension, dizziness, dry mouth, constipation, urinary retention, sedation or somnolence, insomnia, weight gain, edema, sweating, sexual dysfunction, and reduced vitamin B6 levels or pyridoxine deficiency. Hypoglycemia and clinically relevant cytochrome P450 interactions may also occur, particularly with hydrazine MAOIs such as phenelzine. Rare adverse effects reported with phenelzine include hypomania or mania, psychosis, hepatotoxicity, and acute liver failure, the last of which has been reported mainly in susceptible individuals, including people with pre-existing liver damage, old age, long-term effects of alcohol consumption, or viral infection.
The acid mantle is a very thin, delicate, slightly acidic film covering the entire surface of human skin, serving as a protective barrier against pathogens and reduces body odor. The acidic pH at the skin's surface is primarily maintained by free amino acids and α-hydroxy acids (lactic acids) excreted from sweat; free fatty acids and amino acids from sebum; and urocanic acid and pyroglutamic acid. While the viable epidermis below the stratum corneum has a neutral pH of around 7.0, the surface pH of the skin's acid mantle typically ranges between 4.5 and 6.5, with an average assumption of 5.0 to 6.0.
Sources: en.wikipedia.org
== Cultural response == Though intended as a parody, the single popularized the valley girl stereotype nationwide. Following the single's release, there was a significant increase in "valleyspeak" slang usage, whether ironically spoken or not. In particular, the film Valley Girl (1983) capitalized on this cultural curiosity. Zappa expressed concern that, despite his rich body of music, he was seen as a "novelty" artist because of songs like "Valley Girl" and "Don't Eat the Yellow Snow". At the time of the single's release, Moon said, "I am not a valley girl, but I guess that is my claim to fame." Mimi Pond created a comic book about the song, The Valley Girl's Guide to Life, which launched her career. A parody entitled "Valley Dudes" was recorded in 1982 by The Straight A's. On September 16, 2022 (3 months after the single's 40th anniversary), Universal Music Group (who acquired the Zappa catalogue in June of the same year) released an animated music video for the song.
The formal evaluation of the quantitative evidence from two or more trials bearing on the same question. This most commonly involves the statistical combination of summary statistics from the various trials, but the term is sometimes also used to refer to the combination of the raw data. (ICH E9) Monitoring Report
=== Livestock feed === One of the major uses of soybeans globally is as livestock feed, predominantly in the form of soybean meal. In the European Union, for example, though it does not make up most of the weight of livestock feed, soybean meal provides around 60% of the protein fed to livestock. In the United States, 70 percent of soybean production is used for animal feed, with poultry being the number one livestock sector of soybean consumption. The American Soybean Association estimates that over 90% of U.S. soybeans are used as animal feed and 97% of soybean meal feeds livestock and poultry. Spring grasses are rich in omega-3 fatty acids, whereas soy is predominantly omega-6. The soybean hulls, which mainly consist of the outer coats of the beans removed before oil extraction, can also be fed to livestock and whole soybean seeds after processing.
Sources: en.wikipedia.org
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.
AEDG is the one-letter code for the four amino acids alanine, glutamate, aspartate and glycine in that order. The same molecule is written in three-letter form as Ala-Glu-Asp-Gly.
Identity is normally confirmed by mass spectrometry against the calculated mass of roughly 390.35 g/mol. Purity is then estimated by reversed-phase high-performance liquid chromatography with ultraviolet detection.
Reversed-phase high-performance liquid chromatography is run alongside mass spectrometry. The chromatogram separates components and gives a purity figure, while the mass spectrum confirms that the measured molecular mass matches the expected sequence. Neither measurement on its own is treated as sufficient.