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.
Last reviewed on 2025-11-19. Where a claim depends on a specific study, the study is described rather than over-claimed.
Dissolution is usually performed in water or a suitable aqueous buffer, and the resulting liquid is divided into single-use portions before freezing. Freeze-thaw cycling is a recognised source of loss for short peptides, since each cycle can encourage aggregation or adsorption onto container walls. Working solutions are generally kept cold and used within a short window, although published stability data specific to epitalon are thin. Containers should be marked with concentration and date, and solutions examined for cloudiness before use.
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.
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.
Proposed mechanisms centre on cell-culture observations rather than a defined receptor interaction. Several reports describe increased expression of the telomerase catalytic subunit after exposure of cultured human cells, and the authors attributed the effect to short peptide fragments entering the nucleus and influencing gene transcription. No receptor for the tetrapeptide has been identified, and the free peptide is expected to be degraded rapidly by plasma peptidases. Whether any measurable fraction reaches intact tissues after administration remains an unresolved question rather than an established finding.
| Property | Value | Notes |
|---|---|---|
| Sequence | Ala-Glu-Asp-Gly | Written in three-letter amino acid code |
| Single-letter code | AEDG | Form used in most catalogue entries |
| Typical purity specification | 95 percent or higher | Value read from the HPLC chromatogram |
| Storage, dry solid | Minus 20 degrees Celsius, desiccated | Sealed container, protected from light |
| Handling, solution | Divide into single-use portions | Limits losses from freeze-thaw cycling |
No national medicines regulator has approved epitalon as a therapeutic product. It is generally distributed as a research chemical, and in some jurisdictions selling peptides for human consumption without approval is restricted or prohibited. Certificates of analysis accompanying commercial material vary in which tests are performed, and independent verification of identity and purity is uncommon. Statements about anti-ageing or disease-prevention benefits on vendor pages are marketing claims rather than regulatory findings, a distinction that shapes how the compound is discussed in scientific and popular sources alike.
The most frequently cited laboratory finding is that AEDG increased telomerase activity and extended telomere length in cultured human somatic cells. That work used fetal fibroblast strains and reported changes in enzyme activity alongside altered division counts. Replication by unrelated groups has been limited, and the published record is largely a single-laboratory series rather than a multi-centre programme. The result supports a hypothesis about peptide influence on gene expression in cell culture; it does not by itself establish an effect on telomere length in living animals or in people.
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.
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.
With Muir gone, the remaining members continued as a four-piece, releasing Starless and Bible Black in March 1974. Earning a positive Rolling Stone review, most of the album was recorded live during the band's late 1973 tour, with the recordings carefully edited and overdubbed to sound like studio recordings, while "The Great Deceiver", "Lament" and the second half of "The Night Watch" were recorded entirely in the studio. The album reached No. 28 in the UK and No. 64 in the US. Following the album's release, the band began to divide once more, this time over performance. Musically, Fripp found himself positioned between Bruford and Wetton, who played with such force and increasing volume that Fripp once compared them to "a flying brick wall", and Cross, whose amplified acoustic violin was consistently drowned out by the rhythm section, leading him to concentrate more on keyboards. An increasingly frustrated Cross began to withdraw both musically and personally, with the result being that he was voted out of the group following the band's 1974 tour.
Tea is an aromatic beverage prepared by infusion of hot or boiling fresh water with fresh or cured leaves of Camellia sinensis, an evergreen shrub native to East Asia that originated in the borderlands of southwestern China, northeast India and northern Myanmar. Tea has a stimulant effect in humans primarily due to its caffeine content. After plain drinking water, tea is the most widely consumed beverage in the world. There are many varieties of tea according to differences in cultivars, processing and blends; some have a cooling, slightly bitter and astringent flavor, while others have taste profiles that include sweet, nutty, floral or grassy notes. Traditionally, tea is made by steeping loose tea leaves in hot water (usually in a teapot or teacup) for a period of time, or in the case of compressed and fermented tea, via decoction (simmering) in a kettle. Convenient preparations, such as tea bag, infuser and press as well as powdered instant tea such as matcha, konacha and chai latte, are also common. Tea is most commonly consumed as a hot beverage in a plain hot water infusion, although it can also be in mixed drink forms, such as milk tea and butter tea, sometimes sweetened with added sugar or sugar substitutes, or alternatively flavored with salt and spices. In modern times, tea can also be served as a cold beverage in the form of iced tea or in soft drink mixtures such as bubble tea. Early credible record of tea drinking dates to the 3rd century AD, in a Chinese medical text written by Eastern Han dynasty physician Hua Tuo.
The 1960s and 1970s saw a great deal of activity (and expenditure) in the recovery of manganese nodules from the abyssal plains, with varying degrees of success. This does demonstrate, however, that the recovery of minerals from the seafloor is possible and has been possible for some time. Mining of manganese nodules served as a cover story for the elaborate attempt in 1974 by the CIA to raise the sunken Soviet submarine K-129 using the Glomar Explorer, a ship purpose-built for the task by Howard Hughes. The operation was known as Project Azorian, and the cover story of seafloor mining of manganese nodules may have served as the impetus to propel other companies to make the attempt.
== Evolutionary diversity == Most mammals have MHC variants similar to those of humans, who bear great allelic diversity, especially among the nine classical genes—seemingly due largely to gene duplication—though human MHC regions have many pseudogenes. The most diverse loci, namely HLA-A, HLA-B, and HLA-C, have roughly 6000, 7200, and 5800 known alleles, respectively. Many HLA alleles are ancient, sometimes of closer homology to a chimpanzee MHC alleles than to some other human alleles of the same gene. MHC allelic diversity has challenged evolutionary biologists for explanation. Most posit balancing selection (see polymorphism (biology)), which is any natural selection process whereby no single allele is absolutely most fit, such as frequency-dependent selection and heterozygote advantage. Pathogenic coevolution, as a type of balancing selection, posits that common alleles are under greatest pathogenic pressure, driving positive selection of uncommon alleles—moving targets, so to say, for pathogens. As pathogenic pressure on the previously common alleles decreases, their frequency in the population stabilizes, and remain circulating in a large population. Genetic drift is also a major driving force in some species. It is possible that the combined effects of some or all of these factors cause the genetic diversity. Beyond allelic polymorphism, the degree of evolutionary divergence between MHC alleles within individuals also influences immune function.
Therefore, the essence of PseAAC is that on one hand it covers the AA composition, but on the other hand it contains the information beyond the AA composition and hence can better reflect the feature of a protein sequence through a discrete model. Meanwhile, various modes to formulate the PseAAC vector have also been developed, as summarized in a 2009 review article.
Sources: en.wikipedia.org
Benzo[a]pyrene (BaP or B[a]P) is a polycyclic aromatic hydrocarbon (PAH) and the result of incomplete combustion of organic matter at temperatures between 300 and 600 °C (572 and 1,112 °F). The ubiquitous compound can be found in coal tar, tobacco smoke and many foods, especially grilled meats. The substance with the formula C20H12 is one of the benzopyrenes, formed by a benzene ring fused to pyrene. Its diol epoxide metabolites, more commonly known as BPDE, react with and bind to DNA, resulting in mutations and eventually cancer. It is listed as a Group 1 carcinogen by the IARC. In the 18th century a scrotal cancer of chimney sweepers, the chimney sweeps' carcinoma, was already known to be connected to soot.
== Pre-clinical models == Muscle-atrophy can be induced in pre-clinical models (e.g. mice) to study the effects of therapeutic interventions against muscle-atrophy. Restriction of the diet, i.e. caloric restriction, leads to a significant loss of muscle mass within two weeks, and loss of muscle-mass can be rescued by a nutritional intervention. Immobilization of one of the hindlegs of mice leads to muscle-atrophy as well, and is hallmarked by loss of both muscle mass and strength. Food restriction and immobilization may be used in mouse models and have been shown to overlap with mechanisms associated to sarcopenia in humans.
=== Access to healthcare === In 2021, the French Senate's Delegation for Women's Rights reported that women's health was not considered a priority in rural areas, where medical desertification limits access to gynecological care. This can result in delayed care and inadequate cancer screening. France has faced a shortage of medical gynecologists, with some departments lacking them entirely. Medical gynecology, a discipline distinct from obstetrics and specific to France, saw a halt in specialist training from 1984 to 2003 as the country considered aligning with other European healthcare systems that do not maintain this distinction.
Lamb and mutton, collectively sheep meat (or sheepmeat), is meat from the domestic sheep, Ovis aries. It is generally divided into three types: lamb, from sheep in their first year; hogget, from sheep in their second; and mutton, from older sheep. The name "mutton" comes from French language mouton, sheep. Lamb is the most expensive of the three types, and in recent decades, sheep meat has increasingly only been retailed as "lamb", sometimes stretching the accepted distinctions given above. The stronger-tasting mutton is now hard to find in many areas, despite the efforts of the Mutton Renaissance Campaign in the UK. In Australia, the term prime lamb is often used to refer to lambs raised for meat. Other languages, such as French, Spanish, and Italian, make similar or even more detailed distinctions among sheep meats by age and sometimes by sex and diet—for example, lechazo in Spanish refers to meat from milk-fed (unweaned) lambs.
== Genetics == The McLeod phenotype is a recessive mutation of the Kell blood group system. The McLeod gene encodes the XK protein, which is located on the X chromosome, and has the structural characteristics of a membrane transport protein but an unknown function. Absence of the XK protein is an X-linked disease. Mutational variants result in McLeod syndrome either with or without neuroacanthocytosis: the gene on the X chromosome for McLeod syndrome is physically close to the gene for chronic granulomatous disease. As a result, an individual with one relatively small deletion may have both diseases. The phenotype may be present without the syndrome presenting.
Sources: en.wikipedia.org
Strychnine (, STRIK-neen, -nin, US chiefly -nyne) is a highly toxic, colorless, bitter, crystalline alkaloid used as a pesticide, particularly for killing small vertebrates such as birds and rodents. Strychnine, when inhaled, swallowed, or absorbed through the eyes or mouth, causes poisoning which results in muscular convulsions and eventually death through asphyxia. While it is no longer used medicinally, it was used historically in small doses to strengthen muscle contractions, such as a heart and bowel stimulant and performance-enhancing drug. The most common source is from the seeds of the Strychnos nux-vomica tree.
=== Academic career === Bumpus became a Professor of Medicine in the clinical pharmacology division of Johns Hopkins University School of Medicine, with a secondary appointment in the Department of Pharmacology and Molecular Sciences. She started her own laboratory at Johns Hopkins School of Medicine in 2010 as an Assistant Professor of Medicine and Pharmacology, was promoted to Associate Professor in February 2015, and received Professorship in 2020. Bumpus is known for her research on the metabolism of antiviral drugs used to treat HIV-1 and how genetic variations in drug-processing enzymes may impact these drugs' efficacy. She became Hopkins’ inaugural associate dean of institutional and student equity in 2015 and instituted mentoring programs to expand access to resources and opportunities. After holding that role for two years, in July 2017 she transitioned into a role as senior consulting strategist for Academic and Research Diversity, working with the chief diversity officer to develop and implement diversity and inclusion programs across Johns Hopkins School of Medicine. Bumpus received a Presidential Early Career Award for Scientists and Engineers in 2016. In July 2018, she was named as Associate Dean for Basic Research at Johns Hopkins University School of Medicine.
Carry messages between neurons via influence on the postsynaptic membrane. Have little or no effect on membrane voltage, but have a common carrying function such as changing the structure of the synapse. Communicate by sending reverse-direction messages that affect the release or reuptake of transmitters. The anatomical localization of neurotransmitters is typically determined using immunocytochemical techniques, which identify the location of either the transmitter substances themselves or of the enzymes that are involved in their synthesis. Immunocytochemical techniques have also revealed that many transmitters, particularly the neuropeptides, are co-localized, that is, a neuron may release more than one transmitter from its synaptic terminal. Various techniques and experiments such as staining, stimulating, and collecting can be used to identify neurotransmitters throughout the central nervous system.
==== By phosphate ==== In cyanobacteria, inorganic phosphate (Pi) also participates in the co-ordinated regulation of photosynthesis: Pi binds to the RuBisCO active site and to another site on the large chain where it can influence transitions between activated and less active conformations of the enzyme. In this way, activation of bacterial RuBisCO might be particularly sensitive to Pi levels, which might cause it to act in a similar way to how RuBisCO activase functions in higher plants.
Sources: en.wikipedia.org
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.
Long-term holding is usually at minus twenty degrees Celsius in a sealed, desiccated container. A refrigerator is adequate for short intervals before use. Light exposure is normally avoided as well. Allowing a cold container to warm before opening reduces moisture condensation on the contents.
Repeated cycles are generally avoided. Each freeze and thaw can promote aggregation or loss of peptide to container surfaces, which reduces the amount available for later work. Dividing a solution into single-use portions at the outset is the usual way to limit this problem.
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.