If you have been reading about LC-MS/MS 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 2025-12-08. Numbers and descriptions here follow the published literature rather than marketing material.
Biosynthesis proceeds in two ATP-dependent steps. First, glutamate-cysteine ligase joins glutamate and cysteine. Second, glutathione synthetase adds glycine to the intermediate. The pathway is regulated by cysteine availability, enzyme expression, and feedback inhibition by glutathione itself. Liver tissue has a particularly high capacity for synthesis and export. Because the molecule is made inside cells, circulating glutathione reflects a balance of release, uptake, and breakdown rather than simple dietary supply.
Functionally, glutathione supports redox balance by donating electrons and becoming oxidized. It also serves as a cofactor for enzymes such as glutathione peroxidases and glutathione S-transferases. These enzymes participate in peroxide reduction and in conjugation reactions that help process reactive molecules. Separate from antioxidant roles, glutathione can modify protein cysteines through S-glutathionylation, influencing enzyme activity and signaling. Research continues to examine how these chemical roles translate into whole-organism effects.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. Its glutamate-cysteine linkage uses the gamma-carboxyl group of glutamate, a feature that resists standard peptidases. The cysteine residue provides a thiol group, which gives the molecule its reducing character. In cells, glutathione is often the most abundant small-molecule thiol, with concentrations varying widely by tissue and compartment. It exists mainly in a reduced form called GSH, while oxidation produces a disulfide-linked dimer called GSSG.
Glutathione serves as a cofactor for several enzymes, including glutathione peroxidase and glutathione S-transferase. These enzymes help reduce hydrogen peroxide and lipid peroxides, and they conjugate reactive electrophiles for excretion. The molecule also acts as a reservoir for cysteine, an amino acid that is prone to oxidation. In addition, glutathione participates in the metabolism of nitric oxide, leukotrienes, and prostaglandins. Its roles extend to cell signaling, apoptosis, and the regulation of protein function through S-glutathionylation.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine, and it is the most abundant non-protein thiol in most living cells. The reduced form, GSH, carries a sulfhydryl group that can donate electrons, while the oxidized form, GSSG, forms when two GSH molecules link via a disulfide bond. The balance between these two forms helps define the cellular redox environment, and their ratio is often used as an indicator of oxidative stress. Because the sulfhydryl group is reactive, glutathione participates in many cellular processes, including detoxification and protein regulation.
| Property | Value | Notes |
|---|---|---|
| Common name | Glutathione (reduced form) | Often abbreviated GSH |
| Chemical class | Tripeptide | Contains glutamate, cysteine, and glycine |
| Molecular formula | C10H17N3O6S | Refers to the reduced form |
| Molar mass | 307.32 g/mol | Calculated for C10H17N3O6S |
| Appearance | White to off-white powder | Typical laboratory-grade solid |
Biosynthesis occurs in two ATP-dependent steps. The enzyme glutamate-cysteine ligase joins glutamate and cysteine, forming gamma-glutamylcysteine; glutathione synthetase then adds glycine to produce the complete tripeptide. Because the peptide bond from glutamate uses the gamma-carboxyl group, glutathione resists digestion by many ordinary peptidases. Tissues vary in synthesis capacity, and the liver generally contains high concentrations relative to many other organs. This uneven distribution contributes to organ-specific differences in redox buffering and affects how experimental results are interpreted across tissue types.
Glutathione participates in detoxification reactions, amino acid transport, and the maintenance of protein thiols. It serves as a cofactor for several enzymes, including glutathione peroxidases and glutathione S-transferases. In research literature, altered glutathione status appears in studies of aging, infection, metabolic stress, and environmental exposure. Whether low glutathione is a cause, consequence, or marker of such conditions often remains unresolved. Direct measurement in blood or tissue provides a snapshot, but results depend on sample handling, timing, and the method used.
For solid glutathione reagents, storage at low temperature and protection from moisture and light are typical precautions. Aqueous solutions can oxidize over time, and pH affects stability; alkaline conditions generally promote thiol oxidation. Some protocols prepare fresh solutions, while others use antioxidants or chelators to limit metal-catalyzed oxidation. Purity and counterion content can vary among commercial preparations, affecting concentration calculations. Certificates of analysis and validated assays help verify identity and purity.
Measuring glutathione in biological samples requires attention to oxidation, because GSH can convert to GSSG after sample collection. Blood and plasma samples are often treated with acid or alkylating agents to preserve the reduced form. Without stabilization, apparent GSH concentrations can fall while GSSG rises. Differences in sample type, handling delay, and deproteinization method can produce results that are not comparable across studies. Reporting preanalytical details is therefore important for interpreting findings.
Synthesis occurs in two ATP-dependent steps: glutamate-cysteine ligase joins glutamate and cysteine to form gamma-glutamylcysteine, and glutathione synthetase adds glycine to complete the tripeptide. The pathway is feedback-inhibited by GSH and limited by cysteine availability, so cysteine supply often constrains production. Once formed, GSH participates in redox buffering, xenobiotic conjugation, and protein glutathionylation. Glutathione peroxidase uses GSH to reduce hydrogen peroxide and lipid peroxides, yielding GSSG, while glutathione reductase regenerates GSH using NADPH. Glutathione S-transferases conjugate electrophiles to GSH, supporting detoxification and excretion.
Because GSH is central to redox balance, its status is studied in aging, liver disease, neurodegenerative conditions, and metabolic disorders. Observational studies often report lower GSH or higher GSSG in affected tissues, but such associations do not establish that raising glutathione changes disease outcomes. Oral glutathione is digested into amino acids, and whether intact absorption occurs remains debated; precursors such as N-acetylcysteine and cysteine donors are also investigated. Regulatory agencies generally treat glutathione as a dietary supplement, not an approved drug, and clinical claims require evidence from controlled trials.
Storage conditions strongly influence glutathione stability. The solid reduced form is commonly kept desiccated at or below minus twenty degrees Celsius, protected from light and moisture. Aqueous solutions are less stable because the thiol group reacts with dissolved oxygen, and oxidation accelerates at neutral or alkaline pH. Acidic solutions and oxygen-free handling can slow degradation, but repeated freeze-thaw cycles should be avoided. Researchers often verify concentration before use, because apparent losses can arise from oxidation or water uptake.
Measuring glutathione in biological samples requires attention to oxidation and matrix effects. High-performance liquid chromatography with ultraviolet or fluorescence detection can separate reduced and oxidized forms after derivatization. Liquid chromatography with tandem mass spectrometry offers higher specificity and can quantify glutathione alongside related thiols. Because glutathione can oxidize during sample handling, many protocols use rapid acidification with metaphosphoric acid or sulfosalicylic acid. Internal standards help correct for losses during extraction and analysis.
This is a methylation reaction in which palmatine is converted to its corydaline. The methyl group comes from the cofactor, S-adenosyl methionine (SAM), which becomes S-adenosyl-L-homocysteine (SAH). The reaction also requires nicotinamide adenine dinucleotide phosphate (NADPH). The enzyme was characterised from Corydalis cava. This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:protoberberine 13-C-methyltransferase.
In Florida, American kestrels may be eaten by some growth stage of invasive snakes such as Burmese pythons, reticulated pythons, Southern African rock pythons, Central African rock pythons, boa constrictors, yellow anacondas, Bolivian anacondas, dark-spotted anacondas, and green anacondas.
VIP is highly localised in lungs (70%) and binds with alveolar type II (AT II) cells via VPAC1. The biological (vasodilator) activity of vasoactive intestinal peptide (VIP) was discovered in the lungs before the peptide was isolated and chemical identity characterized from intestine. VIP levels are also considerably high in the brain and the gut. It is localized in key sites in the lung, has potent activities on its major functions, and appears to play an important role in pulmonary physiology and disease. The principal localization of VIP-containing neurons in the tracheobronchial tree is in the smooth muscle layer, around submucosal mucous glands and in the walls of pulmonary and bronchial arteries. Immunoreactive VIP is also present in neuronal cell bodies forming microglia that provide a source of intrinsic innervation of pulmonary structures.
GvpA is a gas vesicle structural protein found in different phyla of bacteria and archaea for example in Halobacterium salinarum or Haloferax mediterranei. Gas vesicles are small, hollow, gas filled protein structures found in several cyanobacterial and archaebacterial microorganisms. They allow the positioning of the bacteria at a favourable depth for growth. GvpA associates with GvpC, to build up gas vesicles, hollow protein structures which are used by planktonic organisms to perform vertical migration. GvpA makes up most of the structure, as so called "ribs", rigid β-sheets, whereas GvpC stabilizes the vesicle against collapse by crosslinking as α-helices.
Motilin is a 22-amino acid polypeptide hormone in the motilin family that, in humans, is encoded by the MLN gene. Motilin is secreted by endocrine Mo cells (also referred to as M cells, which are not the same as the M cells, or microfold cells, found in Peyer's patches) that are numerous in crypts of the small intestine, especially in the duodenum and jejunum. It is released into the general circulation in humans at about 100-min intervals during the inter-digestive state and is the most important factor in controlling the inter-digestive migrating contractions; and it also stimulates endogenous release of the endocrine pancreas. Based on amino acid sequence, motilin is unrelated to other hormones. Because of its ability to stimulate gastric activity, it was named "motilin." Apart from in humans, the motilin receptor has been identified in the gastrointestinal tracts of pigs, rats, cows, and cats, and in the central nervous system of rabbits.
Sources: en.wikipedia.org
2-Arachidonoylglycerol (2-AG) is an endocannabinoid, an endogenous agonist of the CB1 receptor and the primary endogenous ligand for the CB2 receptor. It is an ester formed from the omega-6 fatty acid arachidonic acid and glycerol. It is present at relatively high levels in the central nervous system, with cannabinoid neuromodulatory effects. It has been found in bovine and human milk. The chemical was first described in 1994–1995, although it had been discovered some time before that. The activities of phospholipase C (PLC) and diacylglycerol lipase (DAGL) mediate its formation. 2-AG is synthesized from arachidonic acid-containing diacylglycerol (DAG). 2-AG, unlike anandamide (another endocannabinoid), is present at relatively high levels in the central nervous system; it is the most abundant molecular species of monoacylglycerol found in mouse and rat brain (~5–10 nmol/g tissue). Detection of 2-AG in brain tissue is complicated by the relative ease of its isomerization to 1-AG during standard lipid extraction conditions. It has been found in bovine as well as human milk.
Research into virtual reality (VR) hardware and software started as early as 1968 by Ivan Sutherland and his student Bob Sproull, but most equipment was too expensive for consumer use, and its use for games was limited. The first VR head mounted display was connected to a computer. In the late 1980s, Jaron Lanier and Thomas G. Zimmerman, former programmers for Atari, Inc., began developing hardware under the name VPL Research, with Lanier coining the term "virtual reality" for their products. One of VPL's products was the VPL DataGlove; a glove that sensed the user's finger movement and translated it into computer input. The idea inspired engineers at Abrams/Gentile Entertainment (AGE) to work with Mattel and Nintendo to build a low-cost version of the DataGlove to work with the Nintendo Entertainment System (NES), omitting much of the technical sophistication and movement sensitivity of the DataGlove as to achieve a reasonable consumer cost. The Power Glove was released in 1989. The games Super Glove Ball and Bad Street Brawler were specifically designed to use the Power Glove, while other NES games could be played using the Power Glove by mapping its output to various controls. About one million Power Glove units were sold before Mattel discontinued it in 1990. Its low cost compared to the DataGlove and other similar gloves led academics to buy the unit for their own research.
=== Research === Psychiatric research is, by its very nature, interdisciplinary; combining social, biological and psychological perspectives in attempt to understand the nature and treatment of mental disorders. Clinical and research psychiatrists study basic and clinical psychiatric topics at research institutions and publish articles in journals. Under the supervision of institutional review boards, psychiatric clinical researchers look at topics such as neuroimaging, genetics, and psychopharmacology in order to enhance diagnostic validity and reliability, to discover new treatment methods, and to classify new mental disorders. Another thing to consider in research and conducting research in the field of psychiatry is the patients needs and values as Brock mentions their chapter on Informed Consent regarding the need to explain and inform participants about a research study and also act in their best interests, as Hellman and Hellman discuss. This can face challenges, such as dual-conflict roles in which their conflict roles between being a doctor and a researcher, especially in research involving control groups where some participants are not getting a treatment, where treating people as a merely just a means to an end, as discussed in Kantian morals, and not prioritizing their well-being and ensuring they are informed and given the option of treatments available, even those in research with positive predicted outcomes.
In 1974, under the Local Government Act 1972, the administrative county and county borough were abolished and their former area was combined with Westmorland and parts of Lancashire and the West Riding of Yorkshire to form the new county of Cumbria. The area from Cumberland went on to form the districts of Carlisle, Allerdale, Copeland and part of Eden.
Sources: en.wikipedia.org
=== Constituent assembly === One of Castillo's principal goals is to convene the constituent assembly to repeal and rewrite the Fujimori-era constitution. This measure is unlikely to pass in an opposition-controlled Congress. However, Free Peru and the Vice President have been collecting signatures to enact a constituent assembly via referendum. Likewise, the opposition has been gathering signatures against the proposal. Legal experts doubt whether these signatures will allow a constituent assembly to be held. Following the resignation of the Bellido cabinet, Prime Minister Mirtha Vásquez stated that changing the constitution is not a priority, despite it having been one of Castillo's main campaign promises. On 1 December 2021, Free Peru's spokesperson Waldemar Cerrón criticized a proposed Congressional bill which would require constitutional reforms to be "approved by Congress with an absolute majority of the legal number of members" to be submitted for referendum. This proposal would restrict the powers of the constituent assembly.
== Awards and honors == Arthur C. Cope Scholar Award (2024) from the American Chemical Society for his foundational contributions to organic chemistry. Cathay Award (2024) from the Chinese Peptide Society for his work in peptide science. Max Bergmann Kreis Gold Medal (2011) for outstanding contributions in peptide chemistry. Vincent du Vigneaud Award (2010) from the American Peptide Society.
*Iron = ~3 g in males, ~2.3 g in females Of the 94 naturally occurring chemical elements, 76 are listed in the table above. Of the remaining 18, it is not known how many occur in the human body. Most of the elements needed for life are relatively common in the Earth's crust. Aluminium, the third most common element in the Earth's crust (after oxygen and silicon), serves no function in living cells, but is toxic in large amounts, depending on its physical and chemical forms and magnitude, duration, frequency of exposure, and how it was absorbed by the human body. Transferrins can bind aluminium.
=== Generic names === Doxepin is the generic name of the drug in English and German and its INNTooltip International Nonproprietary Name and BANTooltip British Approved Name, while doxepin hydrochloride is its USANTooltip United States Adopted Name, USPTooltip United States Pharmacopeia, BANMTooltip British Approved Name, and JANTooltip Japanese Accepted Name. Its generic name in Spanish and Italian and its DCITTooltip Denominazione Comune Italiana are doxepina, in French and its DCFTooltip Dénomination Commune Française are doxépine, and in Latin is doxepinum. The cis or (Z) stereoisomer of doxepin is known as cidoxepin, and this is its INNTooltip International Nonproprietary Name while cidoxepin hydrochloride is its USANTooltip United States Adopted Name.
The route of administration has only a slight effect on the drug's concentrations in the bloodstream: when given as an intramuscular injection, its bioavailability is 90% (as compared to the 100% availability when given directly into a vein), and its highest concentrations in the blood plasma are reached after about 2.3 hours. In the blood, 85–95% of ertapenem are bound to plasma proteins, mostly albumin. Plasma protein binding is higher for lower concentrations, and vice versa. The drug is only partially metabolized, with 94% circulating in form of the parent substance and 6% as metabolites. The main metabolite is the inactive hydrolysis product with the ring opened. Ertapenem is mainly eliminated via the kidneys and urine (80%) and to a minor extent via the faeces (10%). Of the 80% found in the urine, 38% is excreted as the parent drug and 37% as the ring-opened metabolite. The biological half-life is about 3.5 hours in women, 4.2 hours in men and 2.5 hours in children up to 12 years of age.
Sources: en.wikipedia.org
Glutathione is a sulfur-containing tripeptide made from glutamate, cysteine, and glycine. It is found in most cells and participates in redox balance and detoxification reactions.
No. It is a tripeptide assembled from three amino acids. The term amino acid applies to the individual building blocks, not to the assembled molecule.
It is present in many tissues, with especially high amounts in liver. Intracellular concentrations are generally much higher than those found in blood plasma.
Glutathione is a tripeptide of three amino acids: glutamate, cysteine, and glycine. The cysteine residue provides the sulfhydryl group that gives the molecule its reducing properties.