This is a working overview of Redox buffer, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-03-19 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C10H17N3O6S | Reduced glutathione (GSH); oxidized form differs by disulfide linkage. |
| Molar mass | 307.32 g/mol | Calculated for the reduced tripeptide. |
| Appearance | White to off-white crystalline powder | Typical laboratory reagent description. |
| Solubility | Soluble in water | Aqueous solutions are acidic; solubility depends on pH and salt form. |
| CAS Registry Number | 70-18-8 | Refers to reduced L-glutathione; oxidized form has a different number. |
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.
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 composed of glutamate, cysteine, and glycine, with the unusual gamma-glutamyl linkage between glutamate and cysteine. Its cysteine thiol group makes it a major non-enzymatic antioxidant in cells. The reduced form, GSH, predominates in most intracellular compartments, while the oxidized disulfide form, GSSG, is produced when GSH reduces reactive oxygen species. Intracellular concentrations often reach millimolar levels, whereas plasma concentrations are much lower, typically in the low micromolar range. This gradient reflects active synthesis, transport, and consumption rather than passive distribution.
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.
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.
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.
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In Jewish tradition, honey is a symbol for the new year, Rosh Hashanah. At the traditional meal for that holiday, apple slices are dipped in honey and eaten to bring a sweet new year. Some Rosh Hashanah greetings show honey and an apple, symbolizing the feast. In some congregations, small straws of honey are given out to usher in the new year. Pure honey is considered kosher (permitted to be eaten by religious Jews), though it is produced by a flying insect, a non-kosher creature; eating other products of non-kosher animals is forbidden. It belongs among the parve (neutral) foods, containing neither meat nor dairy products and allowed to be eaten together with either. Early Christians used honey as a symbol of spiritual perfection in christening ceremonies. In Islam, an entire chapter (Surah) in the Quran is called an-Nahl (the Bees). According to his teachings (hadith), Muhammad strongly recommended honey for healing purposes. The Quran promotes honey as a nutritious and healthy food, saying:
== English translations == Robert Potter, 1781 - verse: full text Michael Wodhull, 1782 – verse Edward P. Coleridge, 1891 – prose: full text Theodore Alois Buckley, 1892 – prose: full text Gilbert Murray, 1912 – verse: full text Arthur S. Way, 1912 – verse F. L. Lucas, 1924 – verse Augustus T. Murray, 1931 – prose Countee Cullen, 1935 Moses Hadas and John McLean, 1936 – prose R. C. Trevelyan, 1939 – verse Rex Warner, 1944 – verse Robinson Jeffers, 1946 – verse Ray Mathew, 1953 – verse Peter D. Arnott, 1961 – verse Philip Vellacott, 1963 Rush Rehm, 1973 - prose John Davie, 1996 James Morwood, 1997 – prose Paul Roche, 1998 – verse Ruby Blondell, 1999 – verse George Theodoridis, 2004 – prose: full text Stephen Esposito, 2004 – verse Joseph Goodrich, 2005 – verse: full text Graham Kirby, 2006 – verse (The Bloomsbury Theatre) Diane Arnson Svarlien, 2008 – verse Robin Robertson, 2008 – verse J. Michael Walton, 2008 – prose Ian C. Johnston, 2008 – verse: full text Tom Paulin, 2010 - full text Judith Mossman (classicist), 2011 – prose Brian Vinero, 2012 – rhymed verse: full text Mike Bartlett, 2012 – play Diane Rayor, 2013 David Stuttard, 2014 – prose Alan Chriztopher R. Aranza, 2015 – prose Rachel Kitzinger, 2016 – verse Charles Martin, 2019 Dr. Richard W. Swanson, 2020 – prose Michael Ewans, 2022 – verse
, (also called simply the lifetime) is the expected value of the amount of time before an object is removed from the assembly. Specifically, if the individual lifetime of an element of the assembly is the time elapsed between some reference time and the removal of that element from the assembly, the mean lifetime is the arithmetic mean of the individual lifetimes. Starting from the population formula
=== Fossil fuels === The HIC of oil, gas and coal is an important geochemical tool to study the formation, storage, migration and many other processes. The HIC signal of fossil fuels results from both inheritance of source material and water as well as fractionations during hydrocarbon generation and subsequent alteration by processes such as isotopic exchange or biodegradation. When interpreting HIC data of sedimentary organic matter one must take all the processes that might have an isotope effect into consideration. Almost all the organic hydrogen is exchangeable to some extent. Isotopic exchange of organic hydrogen will reorder the distribution of deuterium and often incorporate external hydrogen. Generally, more mature materials are more heavily exchanged. With effective exchange, aliphatic hydrogen can finally reach isotopic equilibrium at the final stage. Equilibrium fractionation factor varies between hydrogen sites. For example, aliphatic hydrogen isotope fractionation depends on the carbon atom that the hydrogen atom bonds with. To first order, alkyl HIC follows this trend: δDPrimary carbon < δDSecondary carbon < δDTertiary carbon. The fractionation factors between carbon sites also decrease with increasing temperature. This can be potentially used as a thermo-history indicator. The fractionation between whole molecule and water can be estimated by averaging all hydrogen-positions, and this leads to a relatively small variation of equilibrium fractionation between different groups of hydrocarbons and water.
Sources: en.wikipedia.org
=== Water seasoning === Water seasoning is the process of immersing wood in running water, quickly removing sap, followed by air drying. It can reduce the elasticity and durability of the wood and cause it to become brittle. There are competing perspectives, however, such as Thomas Tredgold's assertion that "...timber for the joiner's use is best put in water for some time, and afterwards dried; as it renders the timber less liable to warp and crack in drying. Where strength is required it ought not to be put in water."
=== Noncovalent gas phase interactions === Electrospray ionization is also utilized in studying noncovalent gas phase interactions. The electrospray process is thought to be capable of transferring liquid-phase noncovalent complexes into the gas phase without disrupting the noncovalent interaction. Problems such as non specific interactions have been identified when studying ligand substrate complexes by ESI-MS or nanoESI-MS. An interesting example of this is studying the interactions between enzymes and drugs which are inhibitors of the enzyme. Competition studies between STAT6 and inhibitors have used ESI as a way to screen for potential new drug candidates. Electrospray ionization can even be used for studying protein complexes >1 MDa.
It is likely bloodletting was an antecedent to acupuncture. According to historians Lu Gwei-djen and Joseph Needham, there is substantial evidence that acupuncture may have begun around 600 BC. Some hieroglyphs and pictographs from that era suggests acupuncture and moxibustion were practised. However, historians Lu and Needham said it was unlikely a needle could be made out of the materials available in China during this time period. It is possible that bronze was used for early acupuncture needles. Tin, copper, gold and silver are also possibilities, though they are considered less likely, or to have been used in fewer cases. If acupuncture was practised during the Shang dynasty (1766 to 1122 BC), organic materials like thorns, sharpened bones, or bamboo may have been used. Once methods for producing steel were discovered, it would replace all other materials, since it could be used to create a very fine, but sturdy needle. Lu and Needham noted that all the ancient materials that could have been used for acupuncture and which often produce archaeological evidence, such as sharpened bones, bamboo or stones, were also used for other purposes. An article in Rheumatology said that the absence of any mention of acupuncture in documents found in the tomb of Mawangdui from 198 BC suggest that acupuncture was not practised by that time.
Costunolide synthase is a cytochrome P450 protein containing heme. It requires a partner cytochrome P450 reductase for functional expression. This uses nicotinamide adenine dinucleotide phosphate. The starting material for this sesquiterpene lactone is produced from (+)-germacrene A by the enzyme germacrene A hydroxylase.
Sources: en.wikipedia.org
Autoimmune disease A condition in which the immune system inappropriately attacks a body tissue. Multiple sclerosis, some kinds of rheumatism, lupus, and Type 1 diabetes are examples. The reasons for the immune system misbehavior are not, in general, understood. Autonomic neuropathy Damage to nerves that do not control senses or muscles. These nerves control 'automatic' processes, like heart rate and body temperature. They can be damaged by diabetes, just like 'regular' somatic nerves, but the results are 'system-wide', not just pain or muscle weakness. Balance, intestinal control, blood pressure regulation, sweating, breathing rate, ... are all controlled or influenced by the autonomic nervous system.
== Types == Incubators differ from the U.S. Small Business Administration's Small Business Development Centers (and similar business support programs) in that they serve only selected clients. Congress created the Small Business Administration in the Small Business Act of July 30, 1953. Its purpose is to "aid, counsel, assist and protect, insofar as is possible, the interests of small business concerns." In addition, the charter ensures that small businesses receive a "fair proportion" of any government contracts and sales of surplus property. SBDCs work with any small businesses at any stage of development, and not only with startup companies. Many business incubation programs partner with their local SBDC to create a "one-stop shop" for entrepreneurial support. There are a number of business incubators that have focused on particular industries or on a particular business model, earning them their own name.
Rubidium is the second most electropositive of the stable alkali metals and has a very low first ionization energy of only 403 kJ/mol. It has an electron configuration of [Kr]5s1 and is photosensitive. Due to its strong electropositive nature, rubidium reacts explosively with water to produce rubidium hydroxide and hydrogen gas. As with all the alkali metals, the reaction is usually vigorous enough to ignite metal or the hydrogen gas produced by the reaction, potentially causing an explosion. Rubidium, being denser than potassium, sinks in water, reacting violently; caesium explodes on contact with water. However, the reaction rates of all alkali metals depend upon surface area of metal in contact with water, with small metal droplets giving explosive rates. Rubidium has also been reported to ignite spontaneously in air.
Sources: en.wikipedia.org
GSH is the reduced form of glutathione, with a free thiol group on cysteine. GSSG is the oxidized disulfide form, created when two GSH molecules become linked. The two forms exist together, and their balance is often reported as the GSH/GSSG ratio in laboratory studies.
Glutathione is synthesized inside cells from amino acids rather than being classified as an essential dietary nutrient. Dietary sources can provide glutathione or its precursors, but digestion and absorption alter what reaches tissues. Research continues on how dietary intake relates to cellular glutathione levels.
The liver has high glutathione concentrations and uses the compound in conjugation and antioxidant reactions. These reactions are relevant to the processing of drugs, pollutants, and normal metabolic byproducts. Studies often examine liver glutathione as a marker of oxidative stress or detoxification capacity.
GSH is the reduced form with a free thiol group, while GSSG is the oxidized disulfide-linked dimer. Most assays distinguish the two because their balance reflects redox conditions. The names are not interchangeable.