The short version of LC-MS/MS fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-02-26 and is reviewed periodically as new material appears.
Glutathione is most stable as a dry powder stored cool and dry, but its thiol group is readily oxidized in solution. Aqueous preparations at neutral or alkaline pH lose GSH faster because the thiolate form reacts with dissolved oxygen and metal ions. Acidic conditions, chelating agents, and oxygen exclusion can slow oxidation, while repeated freeze-thaw cycles promote degradation. Light exposure and trace metals also contribute to loss. Laboratories typically validate stability for their own matrices because degradation rates depend on pH, temperature, concentration, and container materials.
Commercial glutathione is available in research-grade, food-grade, and supplement-grade forms, and purity specifications differ accordingly. Certificates of analysis commonly report identity by nuclear magnetic resonance or mass spectrometry, purity by HPLC, residual solvents, and heavy metals. Reference standards with assigned purity support calibration, while isotopically labeled glutathione can serve as an internal standard for mass spectrometry. For supplements, label claims may not be independently verified, and regulatory oversight varies by country. Verification often involves third-party testing for identity, potency, and contaminants.
Quantifying glutathione requires distinguishing GSH from GSSG and preventing oxidation during sample preparation. Common approaches include the enzymatic recycling assay, often called the Tietze method, which measures total glutathione after converting GSSG to GSH. HPLC with ultraviolet or fluorescence detection and LC-MS/MS can separate and quantify both forms, sometimes after derivatization of the thiol group. Blood, plasma, and tissue samples differ in matrix and baseline concentrations, so method validation must account for recovery, linearity, and interference. No single assay is universally standard.
Interpreting glutathione measurements requires attention to pre-analytical variables. The GSSG concentration in a sample can rise artificially during storage or processing, making the GSH/GSSG ratio unreliable if not controlled. Reference ranges vary by specimen type, assay, and population, so comparisons across studies are difficult. Plasma glutathione is low and sensitive to hemolysis, while whole blood reflects primarily erythrocyte content. Many studies measure total glutathione rather than the reduced and oxidized forms separately, which limits conclusions about redox status.
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.
| Property | Value | Notes |
|---|---|---|
| Typical assay | Enzymatic recycling assay (Tietze) | Measures total glutathione after reduction of GSSG. |
| Separation method | HPLC or LC-MS/MS | Can quantify GSH and GSSG separately with appropriate standards. |
| Solid storage | -20 °C, desiccated, protect from light | Dry powder is more stable than aqueous solutions. |
| Solution storage | Acidic pH, -80 °C, aliquot | Reduce oxygen exposure and freeze-thaw cycling. |
| Oxidation product | Glutathione disulfide (GSSG) | Formed by thiol oxidation; often measured as a stress marker. |
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.
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.
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.
Measuring glutathione requires attention to sample preparation because the molecule oxidizes readily. Blood, tissue, and cell samples are often treated with acid to precipitate proteins and stabilize the thiol. Without such steps, GSH can convert to GSSG or form mixed disulfides during storage. Analytical methods include spectrophotometric assays, high-performance liquid chromatography, and mass spectrometry. Each approach has different sensitivity, specificity, and susceptibility to interference from related compounds in complex matrices.
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.
=== Juvenile idiopathic arthritis === Adalimumab has been shown to reduce the signs and symptoms of moderate to severe polyarticular juvenile idiopathic arthritis in children aged four years and older.
In 2008, Air Chief Marshal Sir Glenn Torpy Head of the Royal Air Force, for his part in Operation Telic / Operation Iraqi Freedom. Lieutenant General Sir James Dutton, Royal Marines, "in recognition of meritorious, gallant and distinguished services during coalition operations in Afghanistan". Major General Colin Boag, British Army, "in recognition of gallant and distinguished services during coalition operations in Iraq" (March 2008). Lieutenant General James Bucknall, British Army, "in recognition of gallant and distinguished services during coalition operations in Iraq" (July 2009). Major General Mohamed Elkeshky, Egyptian Army Defense, Military, Naval and Air Attaché to the United States. (2013). In 2011, Vice Admiral Tomohisa Takei, Japan Maritime Self-Defense Force, "as recognition for Takei's exceptional leadership and expertise in maturing and expanding the JMSDF and U.S. Navy partnership during his role as director of operations and plans department, JMSDF Maritime Staff Office from April 2008 to July 2010". In 2013, Lieutenant General Walter Souza Braga Netto, Brazilian Army, Military Attaché to the United States of America. "For exceptionally meritous conduct in the performance of outstanding services from March 2011 to May 2013. In 2014, Air Commodore David Best, United Kingdom Royal Air Force. "For exceptionally meritorious service as Director of Air Operations, International Security Assistance Force, from December 2010 to December 2011". In 2014, Major General Brett Cairns, Canadian Air Force, NORAD J3.
Morgan State University (Morgan State or MSU) is a public historically black research university in Baltimore, Maryland, United States. It is the third largest among all Historically Black Colleges or Universities (HBCUs). In 1890, the university, then known as the Centenary Biblical Institute, changed its name to honor Lyttleton Morgan, the first chairman of its board of trustees and a donor. It became a university in 1975. Although a public institution, Morgan State is not a part of the University System of Maryland. It is a member of the Thurgood Marshall College Fund. It is accredited by the Middle States Commission on Higher Education. and classified among "R2: Doctoral Universities – High research activity".
The non-covalent interactions between antiparallel strands in DNA can be broken in order to "open" the double helix when biologically important mechanisms such as DNA replication, transcription, DNA repair or protein binding are set to occur. The area of partially separated DNA is known as the denaturation bubble, which can be more specifically defined as the opening of a DNA double helix through the coordinated separation of base pairs. The first model that attempted to describe the thermodynamics of the denaturation bubble was introduced in 1966 and called the Poland-Scheraga Model. This model describes the denaturation of DNA strands as a function of temperature. As the temperature increases, the hydrogen bonds between the base pairs are increasingly disturbed and "denatured loops" begin to form. However, the Poland-Scheraga Model is now considered elementary because it fails to account for the confounding implications of DNA sequence, chemical composition, stiffness and torsion. Recent thermodynamic studies have inferred that the lifetime of a singular denaturation bubble ranges from 1 microsecond to 1 millisecond. This information is based on established timescales of DNA replication and transcription. Currently, biophysical and biochemical research studies are being performed to more fully elucidate the thermodynamic details of the denaturation bubble.
Proteins can be informally divided into three main classes, which correlate with typical tertiary structures: globular proteins, fibrous proteins, and membrane proteins. Almost all globular proteins are soluble and many are enzymes. Fibrous proteins are often structural, such as collagen, the major component of connective tissue, or keratin, the protein component of hair and nails. Membrane proteins often serve as receptors or provide channels for polar or charged molecules to pass through the cell membrane. A special case of intramolecular hydrogen bonds within proteins, poorly shielded from water attack and hence promoting their own dehydration, are called dehydrons.
Sources: en.wikipedia.org
Most animals and plants can synthesize vitamin C through a sequence of enzyme-driven steps, which convert monosaccharides to vitamin C. However, some mammals have lost the ability to synthesize vitamin C, notably simians and tarsiers. These make up one of two major primate suborders, haplorrhini, and this group includes humans. The strepsirrhini (non-tarsier prosimians) can make their vitamin C, and these include lemurs, lorises, pottos, and galagos. Ascorbic acid is also not synthesized by at least two species of caviidae, the capybara and the guinea pig. Certain birds and fish do not synthesize their vitamin C. All species that do not synthesize ascorbate require it in the diet. Deficiency causes scurvy in humans, and somewhat similar symptoms in other animals. Animals that can contract scurvy all lack the L-gulonolactone oxidase (GULO) enzyme, which is required in the last step of vitamin C synthesis. The genomes of these species contain GULO as pseudogenes, which serve as insight into the evolutionary past of the species.
In broad terms, spent nuclear fuel has three main components. The first consists of fission products, the leftover fragments of fuel atoms after they have been split to release energy. Fission products come in dozens of elements and hundreds of isotopes, all of them lighter than uranium. The second main component of spent fuel is transuranics (atoms heavier than uranium), which are generated from uranium or heavier atoms in the fuel when they absorb neutrons but do not undergo fission. The actinide series on the periodic table runs from actinium to lawrencium and includes uranium as well as transuranic elements. The third and largest component is the remaining uranium which is around 98.25% uranium-238, 1.1% uranium-235, and 0.65% uranium-236. The U-236 comes from the non-fission capture reaction where U-235 absorbs a neutron but releases only a high energy gamma ray instead of undergoing fission. The physical behavior of the fission products is markedly different from that of the actinides. In particular, fission products do not undergo fission and therefore cannot be used as nuclear fuel. Indeed, because fission products are often neutron poisons (absorbing neutrons that could be used to sustain a chain reaction), fission products are viewed as nuclear 'ashes' left over from consuming fissile materials. Furthermore, only seven long-lived fission product isotopes have half-lives longer than a hundred years, which makes their geological storage or disposal less problematic than for transuranic materials.
=== Dekarangers === The eponymous Dekarangers are members of the S.P.D.'s Earth unit who protect Earth from intergalactic criminals called Alienizers. Each of the primary members possess an SP License (SPライセンス, Esu Pī Raisensu) device, which allows them to transform via Change Mode (チェンジモード, Chenji Mōdo); communicate with each other, analyze items pertaining to a case they are working on, and summon their Deka Machines to battle Kaijuki via Phone Mode (フォンモード, Fon Mōdo); and determine a criminal's innocence in a particular crime and whether or not they can be approved for deletion via Judgement Mode (ジャッジメントモード, Jajjimento Mōdo). While transformed, they each carry a varying pair of D-Arms (ディーアームズ, Dī Āmuzu) sidearms, which can combine to form a firearm-like weapon. They also ride varying Deka Vehicles (デカビークル, Deka Bīkuru) for transportation. After undergoing further training, the primary Dekarangers gain the ability to assume S.W.A.T. Mode (スワットモード, Suwatto Mōdo), which clads them in armor that grants heat-seeking, X-ray, and night vision capabilities. They also wield high-powered D-Revolver (ディーリボルバー, Dī Riborubā) machine guns.
TikTok is a Chinese social networking service and short-form online video platform. It hosts user-submitted videos, which range in duration from three seconds to 60 minutes. It can be accessed through a mobile app or through its website. Since its launch, TikTok has become one of the world's most popular social media platforms, using recommendation algorithms to connect content creators and influencers with new audiences. In April 2020, TikTok surpassed two billion mobile downloads worldwide. The popularity of TikTok has allowed viral trends in food, fashion, and music to take off and increase the platform's cultural impact worldwide. TikTok has come under scrutiny due to data privacy violations, mental health concerns, misinformation, offensive content, addictive algorithm, its role during the Gaza war, and, following its 2026 divestiture in the U.S., alleged censorship of criticism of Donald Trump and discussions of Jeffrey Epstein. While TikTok remains accessible to users in most countries, a minority of countries (including India and Afghanistan) have implemented full or partial bans. Many other countries limit TikTok's use on government-issued devices for security or privacy reasons.
=== Short-loop feedback === Prolactin itself provides negative short-loop feedback by acting on long-form prolactin receptors (PRLR) expressed on TIDA neurons, activating the JAK2–STAT5B signalling cascade. This feedback has two temporal components. Within minutes, prolactin switches TIDA neurons from phasic to tonic firing, increasing dopamine release into the portal vasculature. Over 12–16 hours, prolactin increases tyrosine hydroxylase expression and activity, elevating dopamine synthesis. In PRLR-knockout mice, dopaminergic input to the pituitary is markedly reduced despite severe hyperprolactinaemia, confirming that TIDA tone depends on prolactin feedback.
Sources: en.wikipedia.org
During Botha's term, the SADF began focusing on taking a more aggressive stance to the ongoing war against communist-supported liberation and anti-Apartheid movements in South Africa and Namibia (then South West Africa) and targeting neighboring countries that offered them support. This was partially justified as a new structure intended to turn back a "total onslaught" on the republic from abroad. The post-colonial rise of newly independent black governments on the administration's doorstep created a perceived menace to the existing structure, and Pretoria's occupation of Namibia threatened to bring it into direct confrontation with the world community. On the ground, militant guerrilla movements such as the African National Congress (ANC), South West African People's Organisation (SWAPO) and the Pan Africanist Congress of Azania (PAC) challenged South Africa with force of arms. In 1984, at least 6,000 such insurgents were being trained and armed by Tanzania, Ethiopia, the Soviet Union, and Warsaw Pact member states. In general the struggle went badly for South Africa's opponents. Mozambique provided support and shelter to ANC operatives; in retaliation South African units launched massive counterstrikes which the local security forces were in no position to block. Military aircraft and special forces units deployed across Zimbabwe, Botswana, Lesotho, and Zambia to attack suspected insurgent bases. 30,000 South African military personnel were posted on the Namibian border by late 1985, frequently crossing the frontier to battle SWAPO groups operating from southern Angola.
In animals, biosynthesis begins with the amino acid serine. The sulfur is derived from methionine, which is converted to homocysteine through the intermediate S-adenosylmethionine. Cystathionine beta-synthase then combines homocysteine and serine to form the asymmetrical thioether cystathionine. The enzyme cystathionine gamma-lyase converts the cystathionine into cysteine and alpha-ketobutyrate. This pathway is called the transsulfuration pathway. In plants and bacteria, cysteine biosynthesis also starts from serine, which is converted to O-acetylserine by the enzyme serine transacetylase. The enzyme cysteine synthase, using sulfide sources, converts this ester into cysteine, releasing acetate.
==== Russia ==== On 26 October, a Russian Il-76 transport aircraft under US sanctions landed in Venezuela "after a circuitous route over Africa to avoid Western airspace, according to Flightradar24". The aircraft carried Pantsir-S1 and Buk-M2E air defense systems, according to a Russian official.
== Career == After a postdoctoral fellowship at the University of Southern Denmark in Odense, Mann became group leader at the European Molecular Biology Laboratory (EMBL) in Heidelberg. Later he went back to Odense as a professor of bioinformatics. Since 2005 he has been a director at the Max Planck Institute of Biochemistry in Martinsried near Munich. In addition, he became a principal investigator at the Novo Nordisk Foundation Center for Protein Research in Copenhagen. From his research group in Martinsried originated in 2016 PreOmics, a company commercializing sample prep sets, and EVOSEP, a company commercializing protein analysis equipment. His work has impact in various fields of mass spectrometry-based proteomics:
Sources: en.wikipedia.org
The ratio depends on rapid separation or blocking of GSH before oxidation occurs. GSSG can be formed ex vivo if samples are not processed quickly in cold, acidic conditions. Even small delays can shift the apparent ratio, making standardized protocols essential.
Enzymatic recycling assays measure total glutathione, while HPLC and LC-MS/MS can resolve GSH and GSSG separately. Derivatization or thiol-blocking reagents are sometimes used to stabilize and detect the compounds. Method choice depends on the sample type and required specificity.
Dry glutathione powder is typically stored at -20 °C in a desiccated container protected from light. Solutions should be prepared fresh, kept acidic or frozen, and avoid repeated freeze-thaw cycles. Stability should be confirmed for each specific laboratory condition.
Glutathione oxidizes quickly when cells are disrupted or when samples sit at room temperature. Rapid processing or immediate freezing minimizes the conversion of GSH to GSSG. This step helps ensure that the measured ratio reflects the original biological state.