This is a working overview of redox homeostasis, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-09-14 and is reviewed periodically as new material appears.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. The peptide bond between glutamate and cysteine uses the gamma-carboxyl group of glutamate rather than the alpha-carboxyl group. This unusual linkage protects the molecule from many common peptidases. The cysteine side chain carries a thiol group that can undergo reversible oxidation. Because of this thiol, glutathione participates in redox reactions and helps maintain the reducing environment inside most cells in living systems.
In cells, glutathione exists mainly in a reduced form called GSH. When two GSH molecules react, they form oxidized glutathione, or GSSG, which contains a disulfide bond. The ratio of GSH to GSSG is often used as an indicator of oxidative stress. Enzymes such as glutathione peroxidase and glutathione reductase help cycle the molecule between these two states. This cycling supports antioxidant defense, detoxification of reactive molecules, and regulation of certain signaling pathways.
Glutathione is present in most tissues, with especially high concentrations in the liver. It also serves as a cofactor for some enzymes and helps transport amino acids across cell membranes. In plants and microorganisms, glutathione contributes to stress responses and metal handling. The molecule is synthesized in two ATP-dependent steps, first producing gamma-glutamylcysteine and then adding glycine. Because cysteine availability often limits synthesis, dietary and metabolic factors can influence glutathione levels. Research continues to examine how these levels relate to health and disease.
Glutathione is synthesized in two ATP-dependent steps. First, gamma-glutamylcysteine synthetase links glutamate and cysteine; second, glutathione synthetase adds glycine to form the complete tripeptide. The pathway is feedback-inhibited by GSH itself, which helps maintain steady intracellular levels. Tissues vary widely in glutathione content, with the liver typically containing the highest concentrations, followed by the kidneys, lungs, and erythrocytes. Because cysteine is often limiting, its availability influences synthesis rates, and regulation of this pathway varies by cell type.
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.
| Property | Value | Notes |
|---|---|---|
| Common name | Glutathione | Tripeptide of glutamate, cysteine, and glycine |
| Reduced form | GSH | Dominant intracellular thiol |
| Oxidized form | GSSG | Disulfide-linked dimer |
| Molar mass | 307.32 g/mol | For reduced glutathione |
| Functional motif | Gamma-glutamyl-cysteinyl-glycine | Gamma linkage resists many peptidases |
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.
For solid glutathione, storage conditions affect shelf life. The reduced form is typically kept cool, dry, and protected from air and light. Moisture can promote oxidation, while elevated temperatures accelerate degradation. Suppliers often specify storage at or below freezing, sometimes under inert gas. Solutions are less stable than powders and may require preparation shortly before use. Buffers and chelating agents can slow oxidation, but they do not eliminate it. Published stability data vary with matrix, pH, and container.
Quality control for glutathione focuses on identity, purity, and oxidation state. Certificates of analysis may report assay value, water content, and the presence of GSSG or other impurities. Chromatographic purity is often expressed as a percentage of peak area. Reference standards help laboratories compare results across instruments and batches. Because glutathione is a small, polar molecule, separation from cysteine, gamma-glutamylcysteine, and related thiols can be challenging. Verification often combines more than one analytical technique.
Accurate measurement of glutathione begins with careful sample handling. Because GSH oxidizes rapidly to GSSG, samples must be processed quickly or frozen immediately. Acid precipitation with metaphosphoric acid or perchloric acid is common; it lowers pH, precipitates proteins, and helps preserve the reduced form. Chelating agents such as EDTA can limit metal-catalyzed oxidation. For whole blood, hemolysis releases glutathione from erythrocytes, so plasma and serum values differ substantially from whole blood values.
Several analytical methods can quantify glutathione, including high-performance liquid chromatography (HPLC) with UV or fluorescence detection for separating GSH and GSSG. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) offers higher specificity and sensitivity, often detecting nanomolar concentrations. The enzymatic recycling assay, often called the Tietze method, measures total glutathione by coupling reduction of GSSG to a colorimetric or fluorometric readout. Capillary electrophoresis and electrochemical detection are also used in specialized laboratories. Each method has distinct advantages and limitations regarding throughput, cost, and susceptibility to interference.
== Metabolism and survival == The metabolism of endolithic microorganisms is versatile; genes involved in sulphur metabolism, iron metabolism and carbon fixation have been found in many endolithic communities. Whether they metabolize directly from the surrounding rock, or excrete an acid to dissolve it first is yet undetermined. According to Meslier & DiRuggiero there are genes found in the endolithic community involved in nitrogen fixation. The Ocean Drilling Program found microscopic trails in basalt from the Atlantic, Indian, and Pacific oceans that contain DNA. Photosynthetic endoliths have also been discovered. As water and nutrients are sparse in the endolith's surrounding environment, water limitation is a key factor in the capacity of survival of many endolithic microorganisms. Many of those microorganisms have adaptations to survive in low concentrations of water. Additionally, pigments such as beta carotenes and chlorophyll, especially in cyanobacteria and some algae, help to protect against dangerous radiation and act as a way to obtain energy. Another characteristic is the presence of a very slow reproduction cycle. Early data suggest some only engage in cell division once every hundred years. In August 2013, researchers reported evidence of endoliths in the ocean floor, perhaps millions of years old and reproducing only once every 10,000 years. Most of their energy is spent repairing cell damage caused by cosmic rays or racemization, and very little is available for reproduction or growth.
developmental biology The branch of biology that studies the various processes and phenomena by which organisms (particularly multicellular eukaryotes but not necessarily excluding prokaryotes) grow and develop into mature forms capable of reproduction. In the broadest sense the field may encompass topics such as sexual and asexual reproduction, gametogenesis and sporogenesis, fertilization, embryogenesis, the renewal and differentiation of stem cells into specialized cell types, birth or hatching, metamorphosis, and the regeneration of mature tissues.
== Clinical significance == ALT is commonly measured clinically as part of liver function tests and is a component of the AST/ALT ratio. When used in diagnostics, it is almost always measured in international units/liter (IU/L) or μkat. While sources vary on specific reference range values for patients, 0-40 IU/L is the standard reference range for experimental studies.
The collision/reaction cell is used to remove interfering ions through ion/neutral reactions. Collision/reaction cells are known under several names. The dynamic reaction cell is located before the quadrupole in the ICP-MS device. The chamber has a quadrupole and can be filled with reaction (or collision) gases (ammonia, methane, oxygen or hydrogen), with one gas type at a time or a mixture of two of them, which reacts with the introduced sample, eliminating some of the interference. The integrated Collisional Reaction Cell (iCRC) used by Analytik Jena ICP-MS is a mini-collision cell installed in front of the parabolic ion mirror optics that removes interfering ions by injecting a collisional gas (He), or a reactive gas (H2), or a mixture of the two, directly into the plasma as it flows through the skimmer cone and/or the sampler cone. The iCRC removed interfering ions using a collisional kinetic energy discrimination (KED) phenomenon and chemical reactions with interfering ions similarly to traditionally used larger collision cells.
Sources: en.wikipedia.org
Alimentary Pharmacology & Therapeutics is a bimonthly peer-reviewed medical journal concerned with the effects of drugs on the human gastrointestinal and hepato-biliary systems, particularly with relevance to clinical practice. The journal publishes original papers concerned with all aspects of basic and clinical pharmacology, pharmacokinetics, and the therapeutic use of drugs in the alimentary tract including the liver, gall bladder, and pancreas. Its editors are J. M. Rhodes and C. W. Howden.
== Function == DHX8 is localized in the cellular nucleus and stimulated upon RNA presence. This protein is a component of the spliceosome, so it takes part in pre-mRNA splicing. Splicing is the process of joining exons from primary transcripts of messenger RNA and the elimination of intron sequences, by means of a spliceosomal mechanism, so that the mRNA produced is the one without introns, consisting exclusively of the joined exons. Splicing finishes with the spliceosomal complex disassembly and the ATP-dependent liberation of the resulting mature RNAs to the outer of the nucleus. Spliceosome requires conformational changes to be able to catalyze splicing reactions and the later mature mRNA releasing to the outer of the nucleus. One of the ATP-dependent helicase needed for these conformational changes is DHX8. Furthermore, DHX8 plays a key role in the releasing, facilitating the nuclear export of spliced mRNA. Protein characterization has shown that DHX8 has a binding preference for adenine-rich RNA. This binding is followed by ATP hydrolysis and thus, ADP release.
=== 1968–1974: Early years and debut album === Rush formed in August 1968 in the Willowdale neighbourhood of Toronto, Ontario by guitarist Alex Lifeson, drummer John Rutsey, and bassist/vocalist Jeff Jones. Lifeson and Rutsey had previously collaborated in two short-lived groups, The Lost Cause and The Projection. The trio performed their debut concert in September at the Coff-Inn, a youth centre in the basement of St. Theodore of Canterbury Anglican Church, and were paid CA$25. The group had no name at the time of the booking; "Rush" was suggested by Rutsey's brother, Bill, who felt the moniker was sufficiently concise, which stuck with the band. During this formative period, the band's repertoire consisted primarily of blues-rock covers by artists such as Cream, Jimi Hendrix, and John Mayall. Logistical challenges eventually led to Jones's departure; upon his recommendation, Lifeson's schoolmate Geddy Lee (born Gary Weinrib) assumed the role of bassist and lead vocalist in time for their second gig at the Coff-In. The lineup briefly expanded to a quartet in January 1969 with the addition of multi-instrumentalist Lindy Young, and the band started performing at other drop-in centres and high schools. During this period, they secured professional management with Ray Danniels and agent Vic Wilson. Despite this progress, internal friction resulted in Lee's temporary dismissal.
== Human rights abuses == Throughout the transitional period, the Transitional Government of Ethiopia was criticized by various human rights organizations for abuses ranging from extrajudicial executions to unlawful detentions. At the establishment of the TGE in 1991, when the EPRDF first took power, human rights organizations such as Human Rights Watch and Amnesty International expressed optimism about the future of the state of human rights in Ethiopia. During the previous regime under Mengistu, human rights groups could not exist; following May 1991, however, human rights watchdogs such as the Ethiopian Human Rights Council, the Ethiopian Congress for Democrats, and the human rights committee of the Committee of Eleven were established. However, hopes were quickly dashed following a pattern of rights violations aimed at political dissidents across the country. For instance, at least ten demonstrators in Addis Ababa were killed while protesting the EPRDF in their early days of power. In addition, an estimated 5,000-100,000+ members (including jailed former soldiers) of the previous PDRE were swiftly imprisoned under the TGE. While some were later released, many others were held without being officially charged or having a trial. Members of Mengistu's Workers' Party of Ethiopia were also not permitted to travel abroad or go back to work if they were previously detained by the EPRDF for the duration of the year, but generally found themselves able to do so in 1992.
In 1968, the CCP supported a new system of health care delivery for rural areas. Villages were assigned a barefoot doctor (a medical staff with basic medical skills and knowledge to deal with minor illnesses) responsible for basic medical care. The medical staff combined the values of traditional China with modern methods to provide health and medical care to poor farmers in remote rural areas. The barefoot doctors became a symbol of the Cultural Revolution, for the introduction of modern medicine into villages where traditional Chinese medicine services were used. The barefoot doctor system represents a hybrid of modern and traditional Chinese medicine (Chinese: 中西医结合; lit. 'Chinese western medicine combination', usually translated "Integrative Chinese Medicine"), a guiding principle that has far outlived the barefoot doctor system. Nathan Sivin's 1987 translation of Revised Outline of Chinese Medicine: For Western-medicine practitioners to learn Chinese medicine (新编中医学概要：供西医学习中医用; 1972) serves as a good, though outdated, example of this principle in practice. The State Intellectual Property Office (now known as CNIPA) established a database of patents granted for traditional Chinese medicine. In the second decade of the twenty-first century, Chinese Communist Party general secretary Xi Jinping strongly supported TCM, calling it a "gem". As of May 2011, in order to promote TCM worldwide, China had signed TCM partnership agreements with over 70 countries.
Sources: en.wikipedia.org
=== Start date === Given the significant overlap in historiographical periodisations of Late Roman history, late antiquity, and Byzantine history, there is no consensus on a foundation date for the Byzantine Empire. Scholarship with links to Greece or Eastern Orthodoxy has customarily placed it in the early 300s. The growth of the study of "late antiquity" has led to some historians setting a start date in the seventh or eighth centuries. Others believe a "new empire" began during changes c. 300 AD. Geoffrey Greatrex believes that it is impossible to precisely date the foundation of the Byzantine Empire.
The use of venom across a wide variety of taxa is an example of convergent evolution. In animals, venom usage has evolved independently at least 104 times, across 8 phyla. It is difficult to conclude exactly how this trait came to be so intensely widespread and diversified. The multigene families that encode the toxins of venomous animals are actively selected, creating more diverse toxins with specific functions. Also, a number of animal species have been demonstrated to acquire venom toxins from other sources, notably from associated microbes, which may even inhabit their venom apparatuses. Venoms adapt to their environment and victims, evolving to become maximally efficient on a predator's particular prey (particularly the precise ion channels within the prey). Consequently, some venoms may become specialized to an animal's standard diet.
=== Treatment === Care for a soft tissue injury depends upon the structures that have been injured and the degree of injury. Non-surgical interventions become less effective with the amount of damage or tearing, with complete tears often requiring invasive surgical repair. For most injuries, it is recommended to have an initial period of rest and unloading of the injured part for one to three days, followed by gradual increase in structural load. Many injuries have more specific treatments based upon the damaged muscle, such as shockwave therapy and injections of corticosteroid and saline solutions. A medical professional should evaluate painful injuries and changes in soft tissue function. To make a full diagnosis, they may use nerve conduction studies to localize nerve dysfunction (e.g. carpal tunnel syndrome), assess severity, and help with prognosis. Electrodiagnosis also helps differentiate between myopathy and neuropathy. Magnetic resonance imaging is most commonly used to evaluate soft tissue injuries that may require surgical repair. Immediately following injury, the damaged tissue is often cooled, with some people choosing to continue cooling as a regular part of healing. In recent years, the use of cryotherapy in soft tissue injury management has been challenged extensively. Cooling minimizes the inflammatory process and edema, which is believed to help one recover from a soft-tissue injury. However, prolonged usage of cooling slows healing in animal models. Instead, cooling should be restricted to within 24-48 hours of the injury.
== Treatment == MCTD has no specific treatment. Management should address the individual's primary issues, such as arthritis, skin disease, or visceral involvement. Low-dose glucocorticoids, nonsteroidal anti-inflammatory medications, hydroxychloroquine, or a combination of these therapies can effectively treat many patients. Fever, tiredness, unspecific arthralgias, or myalgias are commonly treated with nonsteroidal anti-inflammatory medications (NSAIDs), hydroxychloroquine, or a low dose of prednisone, depending on the severity. Mild joint involvement can be effectively treated with NSAIDs, hydroxychloroquine, and oral prednisone. Methotrexate has been observed to be useful in more severe cases. If methotrexate is contraindicated, alternative disease-modifying medications for RA, such as leflunomide or azathioprine, may be used. High dosages of corticosteroids are typically effective in treating acute severe myositis. Topical steroids, prednisone, and/or hydroxychloroquine are useful in treating SLE-like skin rash, oral ulcers, and photosensitivity. Steroid treatment is often effective in treating sclerodermatous skin symptoms. Raynaud's phenomenon in MCTD typically responds to vasodilator therapy such as calcium channel blockers, as well as preventive measures including avoiding cold temperatures, smoking, and sympathomimetic drugs. Warming and protecting the fingers are also important. Recent breakthroughs have increased the therapy choices available to people with pulmonary hypertension.
Sources: en.wikipedia.org
Glutathione is a tripeptide made from glutamate, cysteine, and glycine. Its cysteine residue provides a thiol group that is central to its redox activity. The glutamate-cysteine bond forms through the gamma-carboxyl group of glutamate.
Reduced glutathione, GSH, can donate electrons and become oxidized to GSSG. The balance between these forms reflects the cell's redox environment. A shift toward GSSG is commonly interpreted as evidence of oxidative stress, though the ratio can vary by tissue and method.
Glutathione occurs in nearly all cell types, with notable amounts in the liver. It is also present in the lungs, kidneys, and red blood cells. Concentrations differ among tissues and change with age, diet, and disease states.
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.