mass spectrometry comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-05-09. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| 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 compound is described in the literature as a derivative of epithalamin, a preparation obtained from bovine pineal tissue. Work on this peptide family was carried out mainly by a research group in Saint Petersburg beginning in the 1980s, and the substance was later registered for clinical use in Russia under the name Epitalon. Outside that region it is generally treated as a research chemical rather than an approved medicine. Statements about its biological activity rest on a relatively small number of studies, and independent replication remains limited.
In its supplied form epitalon is a white to off-white powder, usually lyophilized and often hygroscopic. It dissolves readily in water and in aqueous buffers, and it is commonly handled as the acetate or trifluoroacetate salt to improve stability during purification and drying. The amide backbone is labile in aqueous media, so solutions are less durable than the dry solid. Handling notes in the chemical literature therefore emphasize keeping the powder dry, cool and shielded from light until it is dissolved.
Epitalon is a synthetic tetrapeptide whose sequence is alanine-glutamate-aspartate-glycine, written in single-letter code as AEDG. The four residues are joined by three peptide bonds, giving a linear backbone with no branching and no disulfide bridges. Its calculated molecular mass for the free form is approximately 390.3 daltons, a figure that rises when the compound is supplied as an acetate or trifluoroacetate salt. Because the chain is short, the molecule is defined entirely by its residue order rather than by any folded three-dimensional structure.
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.
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.
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.
Storage practice centres on limiting moisture, oxygen, and repeated temperature cycling. Freeze-dried powder is generally held desiccated at minus twenty degrees Celsius or colder and protected from light. Reconstituted solutions are markedly less stable, and the aspartate-glycine junction is prone to succinimide formation at neutral to mildly alkaline pH. Portioning material into single-use aliquots reduces degradation compared with repeated freeze-thaw cycles. Stability data specific to this tetrapeptide remain scarce, so most handling guidance is extrapolated from general peptide chemistry rather than measured directly.
Documentation accompanying research peptides usually includes a certificate of analysis listing the batch number, purity figure, and test methods applied. Buyers comparing suppliers should check whether the reported purity refers to chromatographic area or to a mass-balance calculation, because the two are not equivalent. Counter-ion content, residual solvents, and water content are sometimes omitted from such certificates even though they affect the actual peptide mass present. Independent verification through a second laboratory is the most direct way to confirm that a supplied material matches its label.
Purity assessment of peptide reagents normally relies on reversed-phase high-performance liquid chromatography. A gradient of acetonitrile in water with trifluoroacetic acid, paired with a C18 stationary phase, separates the target tetrapeptide from truncated sequences and deletion analogues. Detection at 214 nanometres exploits absorbance of the peptide backbone, since the molecule contains no aromatic residue. Results are expressed as a percentage of total peak area. Values above ninety-five percent are typical for research-grade material, although reporting conventions vary between suppliers.
=== Crime === Moore has blamed his predecessor, Governor Larry Hogan, for increased violent crime in Maryland, citing his lack of collaboration between his administration and local leaders and legislators. During his 2022 gubernatorial campaign, he called on Hogan to target state resources toward preventing gun violence in Baltimore and campaigned on addressing crime in the city through better cooperation between the city and state, and to leverage these relationships on the federal level to bring more resources into the city. In January 2023, Moore told CBS News that he supported a bill that would prohibit charging juveniles with felony murder. In January 2023, following the release of videos capturing the arrest and police assault of Tyre Nichols, Moore condemned the brutality of the police and thanked the United States Department of Justice for opening an investigation into Nichols's death. He later said in an interview that Nichols's death only highlighted the need to tackle injustice head-on. In February 2023, Moore pledged $11 million in funding for the Maryland Coordination and Analysis Center, an agency that serves as a data-sharing platform for law enforcement officials across the state. He also said that his administration would not use a quota system for traffic stops and arrests after a Baltimore Banner investigation found that Maryland State Police supervisors previously demanded troopers hit targets for traffic stops and arrests.
Administratively headquartered in 29 floors of the U.S. Steel Tower in Pittsburgh's Central Business District, UPMC operates as a complete and integrated health provider system that, although legally separate from the University of Pittsburgh, identifies it as a supported organization in its articles of incorporation and remains closely affiliated with the university and its Schools of the Health Sciences including via the existence of mutual board memberships and subsidization of the university's academic programs. Under a collaborative and coordinated decision-making model, UPMC oversees all clinical activity, including a consolidated physicians' practice plan consisting of university faculty, while the University of Pittsburgh remains the guardian of all academic priorities, particularly faculty-based research. UPMC's 24-member Board of Directors equally splits representation between three groups: the University of Pittsburgh, the community at-large, and individuals historically involved in the governance of its system's hospitals. UPMC is composed of three major operating components: Provider Services, Insurance Services, and International and Commercial Services. The latter two divisions include the for-profit health insurance company (UPMC Health Plan) and a for-profit International and Commercial Services Division that seeks to bring health care, management, and technologies to market throughout the world. UPMC is the largest employer in the state of Pennsylvania.
Acid-labile protecting groups Base-labile protecting groups Fluoride-labile protecting groups Enzyme-labile protecting groups Reduction-labile protecting groups Oxidation-labile protecting groups Protecting groups cleaved by heavy metal salts or their complexes. Photolabile protecting groups Double-layered protecting groups Various groups are cleaved in acid or base conditions, but the others are more unusual. Fluoride ions form very strong bonds to silicon; thus silicon protecting groups are almost invariably removed by fluoride ions. Each type of counterion, i.e. cleavage reagent, can also selectively cleave different silicon protecting groups depending on steric hindrance. The advantage of fluoride-labile protecting groups is that no other protecting group is attacked by the cleavage conditions. Lipases and other enzymes cleave ethers at biological pH (5-9) and temperatures (30–40 °C). Because enzymes have very high substrate specificity, the method is quite rare, but extremely attractive. Catalytic hydrogenation removes a wide variety of benzyl groups: ethers, esters, urethanes, carbonates, etc. Only a few protecting groups can be detached oxidatively: the methoxybenzyl ethers, which oxidize to a quinomethide. They can be removed with ceric ammonium nitrate (CAN) or dichlorodicyanobenzoquinone (DDQ).
The performance of these batteries depends on the characteristics of the material that makes up the cathode. Carbon materials have been widely used as cathodes because of their excellent electrical conductivities, large surface areas, and chemical stability. Especially relevant for lithium-air batteries, carbon materials act as substrates for supporting metal oxides. Binder-free electrospun carbon nanofibers are particularly good potential candidates to be used in electrodes in lithium-oxygen batteries because they have no binders, have open macroporous structures, have carbons that support and catalyze the oxygen reduction reactions, and have versatility. Zhu et al. developed a novel cathode that can store lithium and oxygen in the electrode they named nanolithia which is a matrix of carbon nanofibers periodically embedded with cobalt oxide. These cobalt oxides provide stability to the normally unstable superoxide-containing nanolithia. In this design, oxygen is stored as LiO2 and does not convert between gaseous and solid forms during charging and discharging. When the battery is discharging, lithium ions in nanolithia and react with superoxide oxygen the matrix to form Li2O2, and Li2O. The oxygen remains in its solid state as it transitions among these forms. The chemical reactions of these transitions provide electrical energy. During charging, the transitions occur in reverse.
=== Fibrosis === Fibrosis is the scarring of connective tissue, one attribute is the excess deposition of collagen in the extracellular matrix of tissue. Research has shown that HSPs have a role in fibrotic diseases. HSP47 has been shown to be pro-fibrosis in various fibrotic diseases. During the process of fibrosis, HSP47 is expressed and is involved in the production of collagen. HSP47 could be a potential therapeutic agent for fibrotic disease, a down-regulation of HSP47 leads to decreased fibrotic progression.
Sources: en.wikipedia.org
=== Early uses === Animal glue has existed since ancient times, although its use was not widespread. Glue deriving from horse teeth can be dated back nearly 6000 years, but no written records from these times can prove that they were fully or extensively used. The first known written procedures for making animal glue were produced around 2000 BC. Between 1500 and 1000 BC, it was used for wood furnishings and mural paintings, and is found on the caskets of Egyptian pharaohs. Evidence for its use comes in the form of stone carvings depicting glue preparation and use. Egyptian records state that animal glue would be made by melting it over a fire and then applied with a brush. Ancient Greeks and Romans later used animal and fish glue to develop veneering and marquetry, the bonding of thin sections or layers of wood. Animal glue, known as taurokolla (ταυρόκολλα) in Greek and gluten taurinum in Latin, was made from the skins of bulls in antiquity. Broken pottery might also be repaired with the use of animal glues, filling the cracks to hide imperfections. About 906–618 BC, fish, ox horns and stag horns were used to produce adhesives and binders for pigments in China. Animal glues were employed as binders in paint media during the Tang dynasty. They were similarly used on the Terracotta Army figures. Records indicate that one of the essential components of lampblack ink was proteinaceous glue. Ox glue and stag-horn glues bound particles of pigments together, acting as a preservative by forming a film over the surface as the ink dried.
In 1934, Willard Libby reported that he had found weak beta activity in pure neodymium, which was attributed to a half-life over 1012 years. Almost 20 years later, it was claimed that the element occurs in natural neodymium in equilibrium in quantities below 10−20 grams of promethium per one gram of neodymium. However, these observations were disproved by newer investigations, because for all seven naturally occurring neodymium isotopes, any single beta decays (which can produce promethium isotopes) are forbidden by energy conservation. In particular, careful measurements of atomic masses show that the mass difference between 150Nd and 150Pm is negative (−87 keV), which absolutely prevents the single beta decay of 150Nd to 150Pm. In 1965, Olavi Erämetsä separated out traces of 147Pm from a rare earth concentrate purified from apatite, resulting in an upper limit of 10−21 for the abundance of promethium in nature; this may have been produced by the natural nuclear fission of uranium, or by neutron capture of 146Nd. Both isotopes of natural europium have larger mass excesses than sums of those of their potential alpha daughters plus that of an alpha particle; therefore, they (stable in practice) may alpha decay to promethium. Research at Laboratori Nazionali del Gran Sasso showed that europium-151 decays to promethium-147 with the half-life of 5×1018 years; later measurements gave the half-life as (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 1018 years. It has been shown that europium is "responsible" for about 12 grams of promethium in the Earth's crust.
This side effect is mediated by the metabolite norfenfluramine on 5HT2B receptors of heart valves, leading to a characteristic pattern of heart failure following proliferation of cardiac fibroblasts on the tricuspid valve. Both fenfluramine and benfluorex form norfenfluramine as a metabolite. This side effect led to the withdrawal of fenfluramine as an anorectic drug worldwide, and later to the withdrawal of benfluorex in Europe.
== Natural occurrence == Phenethylamine is produced by a wide range of species throughout the plant and animal kingdoms, including humans; it is also produced by certain fungi and bacteria (genera: Lactobacillus, Clostridium, Pseudomonas and the family Enterobacteriaceae) and acts as a potent antimicrobial against certain pathogenic strains of Escherichia coli (e.g., the O157:H7 strain) at sufficient concentrations.
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.
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.