thiol group raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-04-26. Anything still debated is marked as such rather than presented as settled.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. Its cysteine residue carries a thiol group, which allows the molecule to participate in reduction and oxidation reactions. The compound exists in most living cells, where the reduced form, often abbreviated GSH, is usually more abundant than the oxidized disulfide form, GSSG. Intracellular concentrations are commonly in the millimolar range, while extracellular concentrations are much lower. This uneven distribution supports its role as a major cellular redox buffer.
Cells synthesize glutathione through two ATP-dependent enzymatic steps. The first step combines glutamate and cysteine to form gamma-glutamylcysteine, catalyzed by glutamate-cysteine ligase. The second step adds glycine, producing the complete tripeptide, catalyzed by glutathione synthetase. Glutathione itself can inhibit the first enzyme, providing negative feedback when levels are high. Because cysteine is often limiting, its availability influences how quickly the pathway proceeds. These reactions occur in the cytosol, and the resulting glutathione can be distributed to other compartments.
Glutathione functions in redox balance, detoxification, and sulfur amino acid storage. It participates in reactions that help maintain ascorbate and protein thiol status. The molecule serves as a cofactor for several enzymes, including glutathione peroxidases and glutathione S-transferases. These enzymes reduce peroxides and conjugate electrophiles, respectively. Glutathione also contributes to the metabolism of xenobiotics and to the transport of cysteine between tissues. How interorgan transport and tissue-specific regulation shape whole-body pools remains an active area of study.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical formula | C10H17N3O6S | Reduced glutathione (GSH) |
| Molar mass | 307.32 g/mol | Calculated for C10H17N3O6S |
| Appearance | White to off-white powder | Typical solid form |
| Solubility | Water-soluble | Polar tripeptide |
| Common synonyms | GSH; L-glutathione | Gamma-glutamylcysteinylglycine |
Glutathione supports detoxification by conjugating reactive electrophiles through glutathione S-transferases. The resulting conjugates are processed and exported, often after further metabolism. It also stores cysteine, transports amino acids across membranes through the gamma-glutamyl cycle, and assists in the maturation of iron-sulfur clusters and some prostaglandins. In plants, animals, and many microbes, the molecule appears in similar roles, but concentrations vary enormously between tissues. Liver, kidney, and red blood cells tend to contain high amounts, while blood plasma contains much less.
Glutathione is a small tripeptide built from glutamate, cysteine, and glycine. The peptide bond between glutamate and cysteine uses the gamma-carboxyl group, a linkage that resists ordinary peptidases. Cells make it in two ATP-dependent steps: gamma-glutamylcysteine synthetase joins glutamate and cysteine, then glutathione synthetase adds glycine. The pathway is feedback-inhibited by glutathione itself, so intracellular levels tend to stay within a narrow range. Because cysteine is often limiting, sulfur amino acid supply influences how much glutathione a cell can produce.
In its reduced form, glutathione carries a sulfhydryl group that can donate electrons. This property lets it act as a major cellular antioxidant and redox buffer. Glutathione peroxidase uses it to reduce hydrogen peroxide and lipid peroxides, while glutathione reductase regenerates the reduced form using NADPH. The ratio of reduced glutathione to glutathione disulfide is widely used as an indicator of oxidative stress, though the ratio changes with compartment, cell type, and sample handling. Oxidized glutathione can also form mixed disulfides with proteins, affecting their activity.
Synthesis occurs in two ATP-dependent steps. The enzyme glutamate-cysteine ligase joins glutamate and cysteine to form gamma-glutamylcysteine, and glutathione synthetase adds glycine. The first step is rate-limiting and is influenced by cysteine availability and feedback inhibition by GSH. Breakdown involves gamma-glutamyl transferase and subsequent peptidases, which release constituent amino acids for reuse. Because turnover differs among tissues, measurements from blood, plasma, and tissues are not directly interchangeable. Research continues to clarify how compartment-specific pools are regulated in health and disease.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. It contains an unusual gamma-glutamyl bond between glutamate and cysteine, which resists cleavage by many peptidases. The reduced form, GSH, carries a thiol group on cysteine and is the dominant intracellular form in most cells. Its structure allows it to participate in redox reactions and to serve as a sulfur donor. The oxidized form, GSSG, consists of two GSH molecules joined by a disulfide bond.
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.
Glutathione is a small tripeptide made of glutamic acid, cysteine, and glycine. Its cysteine thiol group allows reversible oxidation and reduction, making it central to cellular redox chemistry. The reduced form, often abbreviated GSH, predominates inside most cells, while the oxidized disulfide form, GSSG, forms when two GSH molecules react. The ratio of GSH to GSSG is widely used as an indicator of oxidative stress in laboratory research, though it does not by itself diagnose a clinical condition.
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.
The bioavailability of intranasal fentanyl is about 70–90% but with some imprecision due to clotted nostrils, pharyngeal swallow, and incorrect administration. For both emergency and palliative use, intranasal fentanyl is available in doses of 50, 100, 200, or 400 (PecFent) μg. In emergency medicine, safe administration of intranasal fentanyl with a low rate of side effects and a promising pain-reducing effect was demonstrated in a prospective observational study in about 900 out-of-hospital patients. In children, intranasal fentanyl is useful for the treatment of moderate and severe pain and is well tolerated. Furthermore, a 2017 study suggested the efficacy of fentanyl lozenges in children as young as five, weighing as little as 13 kg. Lozenges are more inclined to be used as the child is in control of sufficient dosage, in contrast to buccal tablets.
=== Drug engineering === By identifying the antigens responsible for a particular immune response, it is possible to identify viable targets for novel drugs. In addition, specific antigens can further be classified based on immunoreactivity for identification of future potential vaccine preparations. In addition to the identification of vaccine candidates, immunoproteomic techniques such as western blotting can additionally be used for measuring the efficacy of a given vaccine.
==== Chain stores ==== Chain stores did not become popular in the United States until the end of World War I. It was reported in 1929 that chain stores accounted for 39% of all grocery sales in the United States. Chain stores' success is related to their ability to undersell smaller distributors. An anti-chain movement arose in response to the success of the chain stores during the Great Depression, but caused little detriment to the success and profitability of the chains.
=== As a food product === Fresh açaí has been consumed as a dietary staple in the region around the Amazon river delta for centuries. The fruit is processed into pulp for supply to food product manufacturers or retailers, sold as frozen pulp, juice, or an ingredient in various products from beverages, including grain alcohol, smoothies, foods, cosmetics and supplements. In Brazil, it is commonly eaten as açaí na tigela. In a study of three traditional Caboclo populations in the Brazilian Amazon, açaí palm was described as the most important plant species because the fruit makes up a major component of their diet, up to 42% of the total food intake by weight.
Sources: en.wikipedia.org
Later, Osborn and Weber pioneered fluorescent antibody staining of cellular substructures, a major technique called indirect immunofluorescence microscopy. In developing the method, they tagged microtubules with specific antibodies, then used fluorescently-tagged secondary antibodies (antibodies to the first set of antibodies) to light up the locations of the microtubules in cells. When they began their work in Germany, the cytoskeleton was not heavily researched. Microtubules and microfilaments were known, and they established that microtubules always reacted with antibodies to tubulins while microfilaments always reacted with antibodies to actin. In the course of their studies, they also found intermediate filaments, slightly thicker than microfilaments, and unreactive to actin antibodies. They developed new antibodies against proteins of the microtubules, intermediate filaments, and microfilaments to use as reagents in examining many types of cells. Many of their antibodies have been licensed to companies for commercial development. Klaus and Osborn used their method to study elements of the cytoskeleton of eukaryotic cells in two dimensions and three dimensions. Osborn has extensively studied microtubules, intermediate filaments, microfilaments, and nuclear proteins as well as other proteins that can associate with these structures. By 1981 Osborn and Klaus had shown conclusively intermediate filaments in different types of cells are different but related, and they can be distinguished using immunofluorescence.
A 2020 review found most men believed the average erect penis length is more than 15.24 cm (6 inches). This inaccurate belief has likely been fed by inaccurate and exaggerated data presented in studies where the size of a participant's erect penis is self-reported. Participants may report overestimates of the size of their penis in the belief that a larger penis is more socially desirable. The same review analyzed the results from ten prior studies where measurements of erect penis size were made by researchers. They reported an erect penis to be between 12.95 and 13.92 cm (5.1 and 5.5 inches, respectively) in length, a result significantly below the average obtained in self-reported studies. The authors commented that results of such measurement studies may still be inflated due to volunteer bias — the possibility that men with larger penises may be more likely to choose to participate in such studies.
The Territorial Army – 1999 – An archive document of The TA in 1999 before the implementation of The Strategic Defence Review. Joslen, H. F. (2003) [1960]. Orders of Battle: Second World War, 1939–1945. Uckfield, East Sussex: Naval and Military Press. ISBN 978-1-84342-474-1. Levy, James P. (2006). Appeasement and Rearmament: Britain, 1936–1939. Lanham: Rowman & Littlefield. ISBN 978-0-742-54537-3. Kiszley, John (2017). Anatomy of a Campaign, The British Fiasco in Norway, 1940. Cambridge: Cambridge University Press. Messenger, Charles (1994). For Love of Regiment 1915–1994. A History of British Infantry. Vol. II. London: Pen & Sword Books. ISBN 978-0-850-52422-2. Messenger, Charles (2005). Call to Arms: the British Army 1914–18. London: Cassell. ISBN 9780304367221. Miller, Russell (2013). Uncle Bill, The Authorised Biography of Field Marshal Viscount Slim. London: Weidenfeld and Nicolson. Perry, Frederick William (1988). The Commonwealth Armies: Manpower and Organisation in Two World Wars. War, Armed Forces and Society. Manchester: Manchester University Press. ISBN 978-0-7190-2595-2. Simkins, Peter (2007) [1988]. Kitchener's Army: The Raising of the New Armies 1914–1916. Barnsley: Pen & Sword Military. ISBN 978-1-844-15585-9. Sebag-Montefiore, Hugh (2006). Dunkirk, Fight to the Last Man. New York: Viking. Sellwood, A. V. (1966). The Saturday Night Soldiers: The Stirring Story of the Territorial Army. London: Wolfe Publishing. Sheppard, Eric (1950). A short history of the British Army (4th ed.). London: Constable.
=== EC 2.9: selenium transferases === EC 2.9 includes enzymes that transfer selenium-containing groups. This category only contains two transferases, and thus is one of the smallest categories of transferase. Selenocysteine synthase, which was first added to the classification system in 1999, converts seryl-tRNA(Sec UCA) into selenocysteyl-tRNA(Sec UCA).
However, the early excitement over nylon also caused problems. It fueled unreasonable expectations that nylon would be better than silk, a miracle fabric as strong as steel that would last forever and never run. Realizing the danger of claims such as "New Hosiery Held Strong as Steel" and "No More Runs", DuPont scaled back the terms of the original announcement, especially those stating that nylon would possess the strength of steel. Also, DuPont executives marketing nylon as a revolutionary man-made material did not at first realize that some consumers experienced a sense of unease and distrust, even fear, towards synthetic fabrics. A particularly damaging news story, drawing on DuPont's 1938 patent for the new polymer, suggested that one method of producing nylon might be to use cadaverine (pentamethylenediamine), a chemical extracted from corpses. Although scientists asserted that cadaverine was also extracted by heating coal, the public often refused to listen. A woman confronted one of the lead scientists at DuPont and refused to accept that the rumour was not true. DuPont changed its campaign strategy, emphasizing that nylon was made from "coal, air and water", and started focusing on the personal and aesthetic aspects of nylon, rather than its intrinsic qualities. Nylon was thus domesticated, and attention shifted to the material and consumer aspect of the fiber with slogans like "If it's nylon, it's prettier, and oh! How fast it dries!".
Sources: en.wikipedia.org
The human immunodeficiency virus (or HIV) is a difficult target to find and eradicate. The earliest tests for infection relied on the presence of antibodies to the virus circulating in the bloodstream. However, antibodies don't appear until many weeks after infection, maternal antibodies mask the infection of a newborn, and therapeutic agents to fight the infection don't affect the antibodies. PCR tests have been developed that can detect as little as one viral genome among the DNA of over 50,000 host cells. Infections can be detected earlier, donated blood can be screened directly for the virus, newborns can be immediately tested for infection, and the effects of antiviral treatments can be quantified. Some disease organisms, such as those for tuberculosis, are difficult to sample from patients and slow to be grown in the laboratory. PCR-based tests have allowed detection of small numbers of disease organisms (both live and dead) in convenient samples. Detailed genetic analysis can also be used to detect antibiotic resistance, allowing immediate and effective therapy. The effects of therapy can also be immediately evaluated. The spread of a disease organism through populations of domestic or wild animals can be monitored by PCR testing. In many cases, the appearance of new virulent subtypes can be detected and monitored. The subtypes of an organism that were responsible for earlier epidemics can also be determined by PCR analysis. Viral DNA can be detected by PCR.
The Cold War was a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc, which began following World War II in 1945. The term cold war is used because there was no large-scale fighting directly between the two superpowers, but they each supported major regional conflicts known as proxy wars. The conflict was based around the ideological and geopolitical struggle for global influence by these two superpowers, following their temporary alliance and victory against Nazi Germany in 1945. Aside from the nuclear arsenal development and conventional military deployment, the struggle for dominance was expressed via indirect means such as psychological warfare, propaganda campaigns, espionage, far-reaching embargoes, rivalry at sports events and technological competitions such as the Space Race.
Removal of pathogens includes encapsulated bacteria, which reduces sepsis risk (see § Complications below). Removal of damaged erythrocytes reduces iron burden from heme via hepatosplenic recycling, which reduces sepsis risk (see Complications below). Removal of damaged erythrocytes continues healthy signaling to bone marrow, where erythropoiesis replaces red blood cells lost to wear and tear. In relation to the three facts above, the spleen misguidedly filters spherocytes – regardless of the age or functional status of the cell. The spleen is not dysfunctional itself when selecting spherocytes for destruction, as this is the regular function of the spleen both at an anatomic structure level, and at the molecular cellular level. At the anatomic level, the passage from the cords of Billroth into the sinusoids may be seen as a "bottleneck", where red blood cells need to be flexible in order to pass through. In HS, the erythrocytes fail to pass through fenestrations, and this is where resident splenic macrophages sample, or "bite", part of the stuck spherocytes' plasma membranes. The macrophages recognize that the spherocyte is not normal, and the macrophage is "programmed" to destroy irregularities filtered at the spleen from the blood. The resident splenic macrophages therefore phagocytose the spherocytes, causing extravascular hemolysis. This leads to both splenomegaly and anemia. Should this process continue unchecked chronically, inappropriate regulation of erythropoiesis leads to extramedullary hematopoiesis.
== Further reading == Carugo, Oliviero; Djinović-Carugo, Kristina (29 June 2023). "Structural biology: A golden era". PLOS Biology. 21 (6) e3002187. doi:10.1371/journal.pbio.3002187. PMC 10337885. PMID 37384774. Curry, Stephen (3 July 2015). "Structural Biology: A Century-long Journey into an Unseen World". Interdisciplinary Science Reviews. 40 (3): 308–328. Bibcode:2015ISRv...40..308C. doi:10.1179/0308018815Z.000000000120. PMC 4697198. PMID 26740732.
== External links == The MEROPS online database for peptidases and their inhibitors: M10.009 Overview of all the structural information available in the PDB for UniProt: P14780 (Matrix metalloproteinase-9) at the PDBe-KB.
Sources: en.wikipedia.org
Glutathione is built from three amino acids: glutamate, cysteine, and glycine. The linkage involves the gamma-carboxyl group of glutamate rather than the alpha-carboxyl group, which is unusual for peptides. This structure protects the bond from some common peptidases.
It is present in nearly all cells, with notable amounts in the liver, kidneys, and red blood cells. The highest intracellular concentrations are usually in the millimolar range. Levels differ by tissue, age, and physiological state.
It is not classified as an essential nutrient because cells can synthesize it from amino acids. Dietary sources exist, but their contribution to tissue pools is not fully established. The body's production depends on enzyme activity and precursor availability.
GSH is the reduced, thiol-containing form of glutathione, while GSSG is the oxidized disulfide dimer formed when two GSH molecules react. Cells maintain a high GSH-to-GSSG ratio under normal conditions. A shift toward GSSG is often interpreted as oxidative stress, though sample handling can affect the measured ratio.