The short version of mass spectrometry fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-09-09 and is reviewed periodically as new material appears.
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.
== Safety and environmental risks == Most anionic and non-ionic surfactants are non-toxic, having LD50 comparable to table salt. The toxicity of quaternary ammonium compounds, which are antibacterial and antifungal, varies. Dialkyldimethylammonium chlorides (DDAC, DSDMAC) used as fabric softeners have high LD50 (5 g/kg) and are essentially non-toxic, while the disinfectant alkylbenzyldimethylammonium chloride has an LD50 of 0.35 g/kg. Prolonged exposure to surfactants can irritate and damage the skin because surfactants disrupt the lipid membrane that protects skin and other cells. Skin irritancy generally increases in the series non-ionic, amphoteric, anionic, cationic surfactants. Surfactants are routinely deposited in numerous ways on land and into water systems, whether as part of an intended process or as industrial and household waste. Anionic surfactants can be found in soils as the result of sewage sludge application, wastewater irrigation, and remediation processes. Relatively high concentrations of surfactants together with multimetals can represent an environmental risk. At low concentrations, surfactant application is unlikely to have a significant effect on trace metal mobility. In the case of the Deepwater Horizon oil spill, unprecedented amounts of Corexit were sprayed directly into the ocean at the leak and on the sea-water's surface. The apparent theory was that the surfactants isolate droplets of oil, making it easier for petroleum-consuming microbes to digest the oil.
=== Depression === An enantiomer of ketamine – esketamine – was approved as an antidepressant by the European Medicines Agency in 2019. Esketamine was approved as a nasal spray for treatment-resistant depression in the United States and elsewhere in 2019. The Canadian Network for Mood and Anxiety Treatments (CANMAT) recommends esketamine as a third-line treatment for depression. Ketamine maintenance therapy appears effective and generally safe for treatment-resistant depression, with regular dosing, early intervention, and concurrent psychotherapy improving outcomes; standardized protocols and patient selection are crucial. The French drug regulatory agency’s 2026 approval of intravenous racemic ketamine for severe suicidal crisis marks the first official rapid-acting pharmacological option for imminent suicide risk. Most systematic reviews suggest that ketamine shows short-term efficacy in reducing suicidality with generally mild side effects, but the evidence is largely low quality and its long-term efficacy remains unclear. Existing evidence, though limited and low to very low certainty, suggests that a single intravenous dose of ketamine as an add-on to mood stabilizers may produce a rapid but transient antidepressant effect in bipolar depression. In February 2022, the US Food and Drug Administration (FDA) issued an alert to healthcare professionals concerning compounded nasal spray products containing ketamine intended to treat depression.
=== Evolution === For at least 1.2 billion years, eukaryotes—a classification of life forms that includes single-cell species, fungi, plants, and animals, but not bacteria, characterized by cells with a membrane-bound nucleus—have been able to synthesize 7-dehydrocholesterol. When this molecule is exposed to UVB light from the sun it absorbs the energy in the process of being converted to vitamin D. The function was to prevent DNA damage, the converted molecule being an end product without vitamin function. Present day, phytoplankton in the ocean photosynthesize vitamin D without any calcium management function, as do some species of algae, lichen, fungi, and plants. Only circa 500 million years ago, when animals began to leave the oceans for land, did the UV-converted molecule take on a hormone function as a promoter of calcium regulation. This function required the development of a nuclear vitamin D receptor (VDR) that binds the biologically active vitamin D metabolite 1α,25-dihydroxyvitamin (D3), plasma transport proteins, and vitamin D metabolizing CYP450 enzymes regulated by calciotropic hormones. The triumvirate of receptor protein, transport and metabolizing enzymes are found only in vertebrates. The initial vitamin function evolved for control of metabolic genes supporting innate and adaptive immunity. Only later did the VDR system start to act as an important regulator of calcium supply for a calcified skeleton in land-based vertebrates.
=== UN treaties and US influence === The three UN drug control conventions, adopted by over 180 countries, provide a legal framework for cooperation between countries. Each state is obligated to incorporate the treaty provisions in their domestic laws. While there is a degree of interpretative flexibility, "each of the treaties encourages – and often requires – that member countries put in place strong domestic penal provisions" to deal with illicit drugs; punitive policies have been the common approach. The US, emerging as the dominant power after WWII, exerted considerable influence over how the conventions were adopted by other nations, promoting a prohibitionist and criminalizing view. Historically, the US has been "the key player in most multilateral negotiations" and the prohibitionist approach "derives largely from U.S. policy – the various forms, past and present, of the U.S. 'war on drugs'". US economic power is focused on the war on drugs through the Foreign Assistance Act (FAA). Enacted in 1961, the FAA integrated various federal foreign aid initiatives under the new US Agency for International Development (USAID), and has remained the core legislation governing foreign financial assistance. In 1972, reacting to concerns over illicit drugs from foreign sources, Congress added an "International Narcotics Control" chapter to the FAA, which allowed the president to enter into agreements and provide assistance for counternarcotic activities in foreign countries.
=== Droplet transportation === Discrete droplets can be transported in a highly controlled way using an array of electrodes. In the same way droplets move from an uncharged electrode to a charged electrode, or vice versa, droplets can be continuously transported along the electrodes by sequentially energizing the electrodes. Since droplet transportation involves an array of electrodes, multiple electrodes can be programmed to selectively apply a voltage to each electrode for a better control over transporting multiple droplets.
Sources: en.wikipedia.org
In general USPTO rejections on the sole grounds of the invention's being "inoperative" are rare, since such rejections need to demonstrate "proof of total incapacity", and cases where those rejections are upheld in a Federal Court are even rarer: nevertheless, in 2000, a rejection of a cold fusion patent was appealed in a Federal Court and it was upheld, in part on the grounds that the inventor was unable to establish the utility of the invention. A U.S. patent might still be granted when given a different name to disassociate it from cold fusion, though this strategy has had little success in the US: the same claims that need to be patented can identify it with cold fusion, and most of these patents cannot avoid mentioning Fleischmann and Pons' research due to legal constraints, thus alerting the patent reviewer that it is a cold-fusion-related patent. David Voss said in 1999 that some patents that closely resemble cold fusion processes, and that use materials used in cold fusion, have been granted by the USPTO. The inventor of three such patents had his applications initially rejected when they were reviewed by experts in nuclear science; but then he rewrote the patents to focus more on the electrochemical parts so they would be reviewed instead by experts in electrochemistry, who approved them. When asked about the resemblance to cold fusion, the patent holder said that it used nuclear processes involving "new nuclear physics" unrelated to cold fusion.
== Fabrication of porous silicon == Anodization and stain-etching are the two most common methods used for fabrication of porous silicon; however, there are almost twenty other methods to fabricate this material. Drying and surface modification might be needed afterwards. If anodization in an aqueous solution is used to form microporous silicon, the material is commonly treated in ethanol immediately after fabrication, to avoid damage to the structure that results due to the stresses of the capillary effect of the aqueous solution.
=== Versions === Chili mac has been a staple dish at American military dining facilities for years. It was introduced to the Meal, Ready-to-Eat (MRE) field ration menu in 1995 and is one of only three of the twelve MRE meals offered in 1995 that has remained on the MRE menu to date. A variation called "taco chili mac" has been consumed by NASA astronauts in space. It is processed by NASA as a freeze-dried product. Hamburger Helper sells a boxed version named "Chili Macaroni".
This tissue may be further divided into two components, the actual fatty layer, or panniculus adiposus, and a deeper vestigial layer of muscle, the panniculus carnosus. The main cellular component of this tissue is the adipocyte, or fat cell. The structure of this tissue is composed of septal (i.e. linear strands) and lobular compartments, which differ in microscopic appearance. Functionally, the subcutaneous fat insulates the body, absorbs trauma, and serves as a reserve energy source. Conditions of the human integumentary system constitute a broad spectrum of diseases, also known as dermatoses, as well as many nonpathologic states (like, in certain circumstances, melanonychia and racquet nails). While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described. Classification of these conditions often presents many nosological challenges, since underlying etiologies and pathogenetics are often not known. Therefore, most current textbooks present a classification based on location (for example, conditions of the mucous membrane), morphology (chronic blistering conditions), etiology (skin conditions resulting from physical factors), and so on.
Sources: en.wikipedia.org
The coffee tree produces fruit often referred to as a coffee cherry, but unlike the cherry, which contains a single pit, it most commonly contains two seeds with their flat sides together. The seeds are referred to as beans because of their appearance, though they are not true beans. A few coffee cherries, referred to as "peaberries" contain a single seed; they make up around 10% to 15% of all coffee beans. It is sometimes asserted that because the single bean does not need to share nutrients between two separated beans, it has a superior flavour profile with bright acidity, sweetness, and concentrated and complex flavours, but there is little evidence to support this; for example, peaberries may have been selected from high-quality beans. Coffee trees range from 5 to 10 m (16 to 33 ft) in height. As the tree gets older, it produces less fruit and slowly loses its resistance to pests and diseases. The coffee beans are in the seeds of fruits from trees and shrubs that originally grew naturally in African forests. Humans produce coffee by roasting, grinding and brewing the raw (green) coffee beans. Coffee plants are often grown in rows spaced apart depending on the desired density chosen by the farmer. Some farmers plant shade trees or cash-crop trees, such as orange trees, around them, or plant the coffee on the sides of hills to provide the conditions coffee needs to flourish.
=== Synthesis of urea === Although not usually isolated as such, the salt ammonium carbamate is produced on a large scale as an intermediate in the production of the commodity chemical urea from ammonia and carbon dioxide.
== Spectrum of activity == Tylosin has a wide spectrum of activity against Gram-positive bacteria including Staphylococcus, Streptococcus, Corynebacterium, and Erysipelothrix. It has a much narrower Gram-negative spectrum of activity, but has been shown to be active against Campylobacter coli, and certain spirochaetes. It has also been shown to be extremely active against Mycoplasma species isolated from both mammalian and avian hosts. The following represents MIC susceptibility data for a few medically significant pathogens:
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.