A practical reference on oxidation state: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-01-28. Anything still debated is marked as such rather than presented as settled.
Common analytical approaches include enzymatic recycling assays, high-performance liquid chromatography, and mass spectrometry. Enzymatic recycling measures total glutathione after converting GSSG back to GSH, while separation methods can quantify GSH and GSSG separately. Derivatization may be used to improve detection or stability during analysis. LC-MS/MS offers high specificity and can distinguish glutathione from related thiols and adducts. Each method has different sensitivity, throughput, and susceptibility to interference, so method selection depends on the study question and sample matrix.
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.
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.
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 |
|---|---|---|
| Typical analytical method | LC-MS/MS, HPLC, or enzymatic recycling | Choice depends on whether total, reduced, or oxidized glutathione is measured. |
| Sample stabilization | Acidification or thiol alkylation | Helps limit conversion of GSH to GSSG after collection. |
| Solution stability | Limited at room temperature | Oxidation and pH-dependent degradation can occur. |
| Storage of solid | -20 °C, desiccated, protected from light | Common for research reagents; follow supplier instructions. |
| Common interference | Other thiols and metal ions | Can affect separation or enzymatic detection. |
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.
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.
Quality control for glutathione materials checks identity, assay, purity, water content, and disulfide content. Commercial products vary from research-grade powder to dietary supplements, and labels may not distinguish reduced from oxidized forms. In the United States, oral glutathione is commonly sold as a dietary supplement rather than an approved drug, while injectable forms fall under different rules and may require a prescription. Regulatory status differs by country. Analytical certificates, when available, help verify what a material contains, but independent testing remains important for interpretation.
Laboratory measurement of glutathione typically starts with rapid acid extraction to prevent oxidation and enzymatic degradation. Common methods include enzymatic recycling assays, high-performance liquid chromatography, and liquid chromatography coupled with mass spectrometry. The recycling assay uses glutathione reductase and a thiol-reactive colorimetric or fluorescent reagent, measuring total glutathione after converting disulfide forms. Chromatographic methods can separate reduced and oxidized forms, which helps when the redox ratio is the target. Choice of method affects sensitivity, specificity, and the amount of sample needed.
Samples for glutathione analysis require careful handling because the compound oxidizes readily and can be consumed by enzymes after collection. Blood is often treated with acid or thiol-blocking agents soon after draw, and plasma should be separated quickly from red blood cells. Tissues are usually snap-frozen or extracted immediately. Aqueous solutions of glutathione are less stable than dry powder and degrade faster at neutral or alkaline pH, in light, or with dissolved oxygen. Repeated freeze-thaw cycles also reduce reliability.
=== Christian Science Monitor libel case === The Christian Science Monitor also published a story on 25 April 2003, stating that it had documentary evidence that he had received "more than ten million dollars" from the Iraqi government. On 20 June 2003, the Monitor reported that its own investigation had concluded that the documents were sophisticated forgeries. Galloway sued The Christian Science Monitor for libel. In March 2004, he accepted damages and a public apology from the Monitor.
As mayor of Nuevo Cuscatlán, Bukele described himself as part of the "radical left" because he wanted "radical changes" ("cambios radicales") for El Salvador; he also stated that his family had always had significant connections with the Salvadoran political left. Bukele believed in social justice and the state obligation to guarantee Salvadorans the opportunity for "health, education, [and] productive infrastructure" ("salud, educación, [e] infraestructura productiva"). Some FMLN members criticized Bukele's work as a businessman, believing that it contradicted the "historic goal of the proletariat" ("papel histórico del proletariado"): eliminating capitalism. Since becoming president, Bukele has stated that he does not adhere to any specific political ideology. He has criticized the political left and right in El Salvador for dividing the country after the civil war. In an interview with Time's Vera Bergengruen, he stated that he did not consider himself either left- or right-wing. El Faro's editorial board has described Bukele as a "politician without an ideology" ("político sin ideología"). Despite Bukele's ostensible ideologic neutrality, some journalists and political analysts have described him as a populist, a right-wing populist, and a conservative. Bukele himself has received support from conservatives abroad in both Latin America and the United States, particularly for his anti-crime policies, as well as criticism for democratic backsliding and consolidating power.
May 13–15 – President Trump makes a state visit to China and meets with Chinese leader Xi Jinping. May 13 – The U.S. Senate confirms Kevin Warsh as the Chair of the Federal Reserve in a 54–45 vote. Warsh will succeed Jerome Powell at the end of the latter's term. May 14 Federal employees sue USDA and Secretary Brooke Rollins on First Amendment grounds over proselytizing Christian messaging in work emails. Mike Banks resigns as U.S. Border Patrol Chief, saying he wanted to spend time with family. Bank's resignation came weeks after the Washington Examiner alleged that he engaged in sex tourism in Colombia and Thailand. May 16 – 2026 Long Island Rail Road strike: Five unions representing over 3,500 workers for the Long Island Rail Road, the largest commuter rail system in North America, go on strike to negotiate a new contract with the Metropolitan Transportation Authority in New York City. May 18 – Five people, including two gunmen, are killed in a mass shooting at a mosque in San Diego, California. May 18–19 – The DOJ announces they reached a settlement with the Internal Revenue Service to resolve Trump's $10 billion lawsuit regarding the 2020 leak of his tax returns to The New York Times. Trump drops the lawsuit but will receive a $1.776 billion "anti-weaponization fund" to give to people who were prosecuted by the Biden administration. A day later, the DOJ reveals that the settlement terms include that the IRS is "forever barred and precluded" from investigating past tax returns filed by President Trump, his family and his businesses. May 19 – U.S.
Sources: en.wikipedia.org
Because lithium-ion batteries can have a variety of positive and negative electrode materials, the energy density and voltage vary accordingly. The open-circuit voltage is higher than in aqueous batteries (such as lead–acid, nickel–metal hydride and nickel–cadmium). Internal resistance increases with both cycling and age, although this depends strongly on the voltage and temperature the batteries are stored at. Rising internal resistance causes the voltage at the terminals to drop under load, which reduces the maximum current draw. Eventually, increasing resistance will leave the battery in a state such that it can no longer support the normal discharge currents requested of it without unacceptable voltage drop or overheating. Batteries with a lithium iron phosphate positive and graphite negative electrodes have a nominal open-circuit voltage of 3.2 V and a typical charging voltage of 3.6 V. Lithium nickel manganese cobalt (NMC) oxide positives with graphite negatives have a 3.7 V nominal voltage with a 4.2 V maximum while charging. The charging procedure is performed at constant voltage with current-limiting circuitry (i.e., charging with constant current until a voltage of 4.2 V is reached in the cell and continuing with a constant voltage applied until the current drops close to zero). Typically, the charge is terminated at 3% of the initial charge current. In the past, lithium-ion batteries could not be fast-charged and needed at least two hours to fully charge. Current-generation cells can be fully charged in 45 minutes or less.
Optical storage uses lasers to store and retrieve data. Recordable CDs, DVDs, and Blu-ray Discs are commonly used with personal computers and are generally cheap. The capacities and speeds of these discs have typically been lower than hard disks or tapes. Advances in optical media may shrink that gap in the future. Potential future data losses caused by gradual media degradation can be predicted by measuring the rate of correctable minor data errors, of which consecutively too many increase the risk of uncorrectable sectors. Support for error scanning varies among optical drive vendors. Many optical disc formats are WORM type, which makes them useful for archival purposes since the data cannot be changed in any way, including by user error and by malware such as ransomware. Moreover, optical discs are not vulnerable to head crashes, magnetism, imminent water ingress or power surges; and, a fault of the drive typically just halts the spinning. Optical media is modular; the storage controller is not tied to media itself like with hard drives or flash storage (→flash memory controller), allowing it to be removed and accessed through a different drive. However, recordable media may degrade earlier under long-term exposure to light. Some optical storage systems allow for cataloged data backups without human contact with the discs, allowing for longer data integrity. A French study in 2008 indicated that the lifespan of typically-sold CD-Rs was 2–10 years, but one manufacturer later estimated the longevity of its CD-Rs with a gold-sputtered layer to be as high as 100 years.
=== Nomenclature === The German chemist Wilhelm Körner suggested the prefixes ortho-, meta-, para- to distinguish di-substituted benzene derivatives in 1867; however, he did not use the prefixes to distinguish the relative positions of the substituents on a benzene ring. It was the German chemist Carl Gräbe who, in 1869, first used the prefixes ortho-, meta-, para- to denote specific relative locations of the substituents on a di-substituted aromatic ring (viz, naphthalene). In 1870, the German chemist Viktor Meyer first applied Gräbe's nomenclature to benzene.
Metabolic studies indicate that NAD, once considered a stable molecule, is continuously turned over and used, requiring tight regulation to maintain metabolic homeostasis. NR utilization in mammals may involve both exogenous dietary sources and endogenous salvage processes that recycle intermediates. NR metabolism and the interactions of different NAD pathways continue to be studied. The NAM and NR pathways involve an amide group and are referred to as 'amidated' pathways. The pathways for de novo synthesis from tryptophan and from NA salvage are 'deamidated' pathways, which share a rate-limiting amidation enzyme NADsynthase1 (NADSYN). Disruptions or imbalances in NAD metabolism have been observed in many disease conditions, and the possibility of restoring NAD levels by administering NAD precursors is an area of interest for researchers.
Sources: en.wikipedia.org
== See also == List of investigational drugs List of investigational generalized anxiety disorder drugs List of investigational panic disorder drugs List of investigational social anxiety disorder drugs List of investigational anxiety disorder drugs Ibogaine
Gallium (68Ga) gozetotide or Gallium (68Ga) PSMA-11, is a radiopharmaceutical made of 68Ga conjugated to a inhibitor of the enzyme prostate-specific membrane antigen (PSMA) known as Glu-Urea-Lys(Ahx)-HBED-CC. It is used for imaging prostate cancer by positron emission tomography (PET). The PSMA inhibitor specifically directs the radiolabeled imaging agent towards the prostate cancerous lesions in men. The most common side effects with gallium (68Ga)-radiolabelled gozetotide are tiredness, nausea (feeling sick), constipation and vomiting. Gallium (68Ga) gozetotide was approved for medical use in the United States in December 2021, and in the European Union in December 2022. It is the first drug approved by the US Food and Drug Administration (FDA) as a PET imaging agent of prostate-specific membrane antigen (PSMA) positive lesions in men with prostate cancer.
== History == Catalase was first noticed in 1818 by Louis Jacques Thénard, who discovered hydrogen peroxide (H2O2). Thénard suggested its breakdown was caused by an unknown substance. In 1900, Oscar Loew was the first to give it the name catalase, and found it in many plants and animals. In 1937 catalase from beef liver was crystallized by James B. Sumner and Alexander Dounce and the molecular weight was measured in 1938. The amino acid sequence of bovine catalase was determined in 1969, and the three-dimensional structure in 1981.
Algae ( AL-jee, UK also AL-ghee; sing.: alga ) are any of a large and diverse group of photosynthetic organisms. It excludes the land plants (embryophytes). Such organisms range from microscopic unicellular microalgae (including cyanobacteria and phytoplankton) to seaweeds, multicellular macroalgae which may grow up to 50 metres (160 ft) in length. Most algae are aquatic (especially marine), and some form cohesive colonies. Freshwater algae include Charophyta such as the filamentous Spirogyra and the grasslike stoneworts. Most algae are plankton carried passively by water, although some macroalgae have holdfasts for anchorage. Algae are polyphyletic as they have multiple evolutionary origins. Although algae with two-membraned chloroplasts seem to form a paraphyletic group within the clade Archaeplastida, other algae with chloroplasts that have three or more membranes evolved from protists that acquired photosynthesis after engulfing archaeplastids. Chlorophytes, rhodophytes (red algae) and glaucophytes (grey algae) have primary chloroplasts directly derived from endosymbiont cyanobacteria, while diatoms, cryptomonads, euglenoids and phaeophyceae (brown algae) have secondary chloroplasts derived from indirectly endosymbiont red algae or green algae. Most algae are single-celled organisms without roots, leaves, or stems. Most are photoautotrophs and the main primary producers of aquatic ecosystems, although some are mixotrophs that derive metabolic energy both from internal photosynthesis and from foraging external nutrients.
Adrenaline, also known as epinephrine and alternatively spelled adrenalin, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands and by a small number of neurons in the medulla oblongata. It plays an essential role in the fight-or-flight response by increasing blood flow to muscles, heart output by acting on the SA node, pupil dilation response, and blood sugar level. It does this by binding to alpha and beta receptors. It is found in many animals, including humans, and some single-celled organisms. It has also been isolated from the plant Scoparia dulcis found in Northern Vietnam.
Sources: en.wikipedia.org
Preanalytical factors such as sample type, time to processing, and stabilization method can change GSH and GSSG amounts. Analytical method and calibration also contribute to variation. Comparing absolute values across studies requires caution.
These assays typically measure total glutathione after oxidizing or reducing steps convert GSSG to GSH. A colorimetric or fluorometric signal is proportional to the recycling reaction. They generally do not report GSH and GSSG separately unless additional steps are used.
Solutions are often prepared fresh and kept cold, with protection from light and oxygen exposure. Chelating agents may reduce metal-catalyzed oxidation. Storage recommendations vary by buffer, pH, and concentration, so protocol-specific guidance should be followed.
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.