The short version of thiol fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-04-22 and is reviewed periodically as new material appears.
Enzymatic recycling assays provide a complementary approach for total glutathione. In these methods, glutathione reductase reduces oxidized glutathione while a thiol-reactive reagent, such as 5,5'-dithiobis(2-nitrobenzoic acid), produces a colored product. The reaction cycles between reduced and oxidized forms, amplifying the signal. Spectrophotometric or fluorometric detection can then estimate concentration. Distinguishing reduced glutathione from glutathione disulfide often requires separate aliquots, masking agents, or chromatographic separation, and the choice affects reported values.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Solid storage temperature | -20 °C | Desiccated, protected from light |
| Solution stability | Hours to days at neutral pH | Acidic pH and low oxygen slow oxidation |
| Oxidized form | Glutathione disulfide (GSSG) | Formed by thiol oxidation |
| Typical analytical method | LC-MS/MS or enzymatic recycling | Choice depends on matrix and specificity |
| Thiol pKa | Approximately 9.2 | Influences reactivity at physiological pH |
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.
Measuring glutathione in biological samples requires attention to oxidation, because GSH can convert to GSSG after sample collection. Blood and plasma samples are often treated with acid or alkylating agents to preserve the reduced form. Without stabilization, apparent GSH concentrations can fall while GSSG rises. Differences in sample type, handling delay, and deproteinization method can produce results that are not comparable across studies. Reporting preanalytical details is therefore important for interpreting findings.
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.
=== Metabolism === Among the many metabolic processes in which it participates, glutathione is required for the biosynthesis of leukotrienes and prostaglandins. It plays a role in cysteine storage. Glutathione enhances the function of citrulline as part of the nitric oxide cycle. It is a cofactor and acts on glutathione peroxidase. Glutathione facilitates metabolism of xenobiotics. Glutathione S-transferase enzymes catalyze its conjugation to lipophilic xenobiotics, facilitating their excretion or further metabolism. The conjugation process is illustrated by the metabolism of N-acetyl-p-benzoquinone imine (NAPQI). NAPQI is a reactive metabolite formed by the action of cytochrome P450 on paracetamol (acetaminophen). Glutathione conjugates to NAPQI, and the resulting ensemble is excreted. As a result of this reaction, cellular glutathione concentration tends to be depleted in the presence of acetaminophen.
=== Imaging === Magnetic resonance imaging (MRI) is the preferred modality for the evaluation of back pain and visualization of bone, soft tissue, nerves and ligaments. X-rays are a less costly initial option offered to patients with a low clinical suspicion of infection or malignancy, and they are combined with laboratory studies for interpretation. Imaging is not warranted for most patients with acute back pain. Without signs and symptoms indicating a serious underlying condition, imaging does not improve clinical outcomes in these patients. Four to six weeks of treatment is appropriate before consideration of imaging studies. If a serious condition is suspected, MRI is usually most appropriate. Computed tomography is an alternative if MRI is contraindicated or unavailable. In cases of acute back pain, MRI is recommended for those with major risk factors or clinical suspicion of cancer, spinal infection or severe progressive neurological deficits. For patients with subacute to chronic back pain, MRI is recommended if minor risk factors exist for cancer, ankylosing spondylitis or vertebral compression fracture, or if significant trauma or symptomatic spinal stenosis is present. Early imaging studies during the acute phase do not improve care or prognosis. Imaging findings are not correlated with severity or outcome.
== M == Maillard reaction Madelung synthesis Malaprade reaction, Periodic acid oxidation Malonic ester synthesis Mannich reaction Markó–Lam deoxygenation Markovnikov's rule, Markownikoff rule, Markownikow rule Marschalk reaction Martinet dioxindole synthesis McDougall monoprotection McFadyen–Stevens reaction McMurry reaction Meerwein arylation Meerwein–Ponndorf–Verley reduction Meisenheimer rearrangement Meissenheimer complex Menshutkin reaction Metal-ion-catalyzed σ-bond rearrangement Mesylation Merckwald asymmetric synthesis Metallo-ene reaction Methylation Meyer–Hartmann reaction Meyer reaction Meyer synthesis Meyer–Schuster rearrangement Michael addition Michael addition, Michael system Michael condensation Michaelis–Arbuzov reaction Midland Alpine borane reduction Mignonac reaction Milas hydroxylation of olefins Minisci reaction Mislow–Evans rearrangement Mitsunobu reaction Miyaura borylation Modified Wittig-Claisen tandem reaction Molisch's test Mozingo reduction Mukaiyama aldol addition (Mukaiyama reaction) Mukaiyama hydration Myers' asymmetric alkylation
== History == Deramciclane was discovered by EGIS Pharmaceuticals Ltd in Budapest, Hungary. In 2000, EGIS signed over exclusive rights to Orion Pharma to further develop, register, and market deramciclane. Successful pre-clinical, Phase I, and Phase II trials looked promising to the company and its investors even up until the third quarter of 2002. Phase I studies show little to no side effects of deramciclane. Phase II studies show little to no side effects and statistically significant improvement on the Hamilton Anxiety Rating Scale in response to daily 60 mg doses, but not in response to daily 10 or 30 mg doses. Finally, in February, 2003, deramciclane development for use against general anxiety disorder (GAD) was discontinued during Phase III trials due to clinically insignificant results compared to placebo groups.
In one study in aged men with prostate cancer, testosterone levels were initially suppressed by 70%, but increased to 50% of baseline levels between 6 and 12 months, remaining stable thereafter up to 24 months of therapy. The combination of progestogens like CPA with an estrogen is synergistic in terms of antigonadotropic effect, and is able to fully suppress gonadal testosterone production even with very small doses of the estrogen. One study found that 100 to 300 mg/day CPA combined with an "extremely low" dosage of diethylstilbestrol (0.1 mg/day), a nonsteroidal estrogen, suppressed testosterone levels into the castrate range (to 30 ng/dL) in men with prostate cancer. Discontinuation of diethylstilbestrol at 5 months resulted in a rapid 6-fold increase in testosterone levels (to 135 ng/dL) and then further (to almost 200 ng/dL) by 12 months. Another study likewise found that the combination of 160 mg/day oral megestrol acetate, a progestin closely related to CPA, with 0.5 to 1.5 mg/day oral estradiol suppressed testosterone levels into the castrate range in men with prostate cancer. A study by Fung and colleagues (2017) found no difference in suppression of circulating testosterone levels (~95% suppression) in transgender women by the combination of either 25 mg/day oral CPA or 50 mg/day oral CPA with a moderate dosage of oral or transdermal estradiol (mean 3.3 mg/day oral, 3.4 g/day gel, or 95.6 μg/day patches).
Sources: en.wikipedia.org
== Diagnosis == A presumptive clinical diagnosis of FPLV can be made for kittens with appropriate signalment, history, clinical findings and the history of no prior vaccination. The clinical diagnosis is usually supported by documenting parvovirus antigen in feces by ELISA (enzyme-linked immunosorbent assay) and PCR (polymerase chain reaction) assays. The availability of validated assays varies by country but is becoming more common. PCR assays are so sensitive that FPV DNA can be amplified from feces of cats vaccinated with modified live strains of the virus. Attenuated parvoviruses in MLV vaccines replicate in the blood and intestine, and post-vaccinal fecal shedding of FPV has been demonstrated, which can result in recent vaccinations giving false positive results on diagnostic tests. At least one of the ELISA antigen tests for dogs (SNAP®Parvo; IDEXX Laboratories) detects FPV in feline feces and has a cut point for a positive test result that excludes most vaccinated cats. Thus, this ELISA is superior to PCR for screening cats for FPV infection and can also be performed in the veterinary clinic. (These are only approved and licensed for detecting canine parvovirus, but it is generally known that they also detect FPL viral antigen in feline feces. These tests are used extra-label because they allow rapid, inexpensive, in-house detection of the virus.) Positive fecal SNAP test results, including weak positives, are highly likely to be true positives in clinically affected animals.
=== Ultraviolet (UV) inactivation === UV rays can damage the DNA of living organisms by creating nucleic acid dimers. However, the damages are usually not important due to low penetration of UVs through living tissues. UV rays can be used, however, to inactivate viruses since virus particules are small and the UV rays can reach the genetic material, inducing the dimerisation of nucleic acids. Once the DNA dimerised, the virus particules cannot replicate their genetic material which prevent them from spreading. UV light in combination with riboflavin has been shown to be effective in reducing pathogens in blood transfusion products. Riboflavin and UV light damages the nucleic acids in viruses, bacteria, parasites, and donor white blood cells rendering them unable to replicate and cause disease.
At the Game Developers Conference in March 2015, Valve and Taiwanese electronics company HTC unveiled SteamVR and the HTC Vive—a virtual reality platform and a virtual reality headset. The platform would be distinguished by its "Lighthouse" motion tracking system, where sensors on the headset and its included motion controllers read the position of two base station devices mounted in the play area. This would allow for "room-scale" VR experiences, where the player would not be required to remain in a stationary position in front of a camera and would be able to freely walk around the space. In November 2017, Microsoft added beta support for the SteamVR service for Windows Mixed Reality headsets. In June 2019, Valve released its own VR headset, known as the Valve Index, positioned as a higher-end device with wider field of view and higher refresh rate. They were accompanied by updated motion controllers, which are strapped against the user's palms and have sensors to detect input pressure and individual fingers. In November 2025, Valve announced the Steam Frame, a standalone VR headset.
The death of Ali Khamenei triggered an election for a new supreme leader. Under the terms of Iran's constitution, the Interim Leadership Council was established on 1 March to exercise the functions of Iran's head of state until a new supreme leader is elected. Mojtaba Khamenei was elected on 8 March 2026 to replace his father as supreme leader, and the IRGC, as well as Iran's top leaders, including Mohammad Bagher Ghalibaf, Ali Larijani, and Masoud Pezeshkian, pledged their allegiance to him. In late March, the NYT described Iran's leadership as paralyzed with severely disrupted decision-making process. It also reported that the damage to communications infrastructure caused paranoia and internal power struggles. As of 21 May, Khamenei remains in hiding and the de facto ruler is uncertain. The IRGC is currently under command of the hardliner general Ahmad Vahidi, who is cited as the formulator of Iran's military and negotiation stance. The Telegraph has revealed a shadowy partnership with the retired IRGC commander-in-chief Mohammad Ali Jafari.
== Incidents == The Aviation Safety Network listed four incidents between 1976 and 1987, one involving a Douglas DC-3, a Douglas DC-4 that was shot down by a Surface-to-air missile and the remaining two with the C-130 Hercules transports, one crashing during a routine takeoff, the other during a landing. In 2004, while transporting journalists and UN officials to a tarmac meeting with Kofi Annan, one of the Chadian helicopters malfunctioned and made a rough landing in the desert.
Sources: en.wikipedia.org
CaSO4 · 2 H2O → CaSO4 · 1/2 H2O + 1+1/2 H2O↑ The endothermic property of this reaction is relevant to the performance of drywall, conferring fire resistance to residential and other structures. In a fire, the structure behind a sheet of drywall will remain relatively cool as water is lost from the gypsum, thus preventing (or substantially retarding) damage to the framing (through combustion of wood members or loss of strength of steel at high temperatures) and consequent structural collapse. But at higher temperatures, calcium sulfate will release oxygen and act as an oxidizing agent. This property is used in aluminothermy. In contrast to most minerals, which when rehydrated simply form liquid or semi-liquid pastes, or remain powdery, calcined gypsum has an unusual property: when mixed with water at normal (ambient) temperatures, it quickly reverts chemically to the preferred dihydrate form, while physically "setting" to form a rigid and relatively strong gypsum crystal lattice:
Once wheat gluten had been isolated as the source of the problems, federal investigators in the United States began to trace the gluten used in the foods. All of the gluten came from ChemNutra's Kansas City warehouse. ChemNutra said it had imported nearly 800 tonnes of wheat gluten from the Xuzhou Anying Biologic Technology Development Company of Xuzhou, Jiangsu, China between 29 November and 8 March. ChemNutra says the gluten came directly from China or from China through the Netherlands, and that the company had received no reports of contamination in the chemical analysis provided by Xuzhou Anying Biologic Technology Development Company. The products were shipped from the company's Kansas City warehouse to several pet food manufacturers and one distributor of pet food ingredients in the US and Canada, including the companies affected by the recall. Xuzhou Anying also exports carrots, garlic, ginger, corn protein powder, vegetables and feed. On 5 April 2007, several days after the United States halted all wheat gluten imports, the Chinese government categorically denied any connection to the North American food poisonings to The New York Times, claiming they had no record of exporting any agricultural products that could have tainted the recalled pet foods, including the wheat gluten that had been the focus of the investigation. The general manager of the Xuzhou Anying Biologic Technology Development Company also denied that they had exported any wheat gluten to North America.
== Methods == Forensic chemists rely on a multitude of instruments to identify unknown substances found at a scene. Different methods can be used to determine the identity of the same substance, and it is up to the examiner to determine which method will produce the best results. Factors that forensic chemists might consider when performing an examination are the length of time a specific instrument will take to examine a substance and the destructive nature of that instrument. They prefer using nondestructive methods first, to preserve the evidence for further examination. Nondestructive techniques can also be used to narrow down the possibilities, making it more likely that the correct method will be used the first time when a destructive method is used.
According to this notion, after the fall of the Christian stronghold of Acre in 1291 and the subsequent persecution by the victorious Mamluks, these crusaders sought refuge in the mountains of Lebanon and settled there permanently. The only early Arab historian who mentions the Druze is the eleventh century Christian scholar Yahya of Antioch, who clearly refers to the heretical group created by ad-Darazī, rather than the followers of Hamza ibn 'Alī. Yahya of Antioch was a Melkite Christian physician and historian of the 11th century. He was most likely born in Fatimid Egypt. He became a physician, but the anti-Christian policies of Caliph Al-Hakim bi-Amr Allah (r. 996–1021) forced him to flee to Byzantine-held Antioch. The life of Hamza ibn Ali and his exact role in the birth of the Druze movement are not entirely clear, as the chief sources about him—the contemporary Christian chronicler Yahya of Antioch, the Muslim historian Ibn Zafir, and Hamza's own epistles—are often contradictory.
Bicalutamide has an antiandrogenic efficacy that is comparable to or greater than that of flutamide, and would be expected to produce similar therapeutic benefits. Other androgen-dependent skin and hair conditions, such as seborrhea and pattern hair loss, may also be treated by bicalutamide. In addition to acne, flutamide has been found to produce an 80% or greater decrease in scores of seborrhea and androgen-dependent scalp hair loss. Moreover, in combination with a combined birth control pill, flutamide treatment resulted in an increase in cosmetically acceptable scalp hair density in almost all women suffering from pattern hair loss in one small study. Bicalutamide is an appealing alternative to flutamide for the treatment of androgen-dependent skin and hair conditions in women because flutamide has a considerable risk of serious liver toxicity, which bicalutamide does not share. Antiandrogens like flutamide and bicalutamide are male-specific teratogens which can feminize male fetuses due to their antiandrogen effects. For this reason, they are not recommended by the U.S.Tooltip United States Food and Drug Administration for use in women. Because of this risk, it is strongly recommended that antiandrogens only be used to treat women who are of reproductive age in conjunction with adequate contraception. Birth control pills, which contain an estrogen and a progestin, are typically used for this purpose.
Sources: en.wikipedia.org
Chromatographic methods can separate the two forms before detection. Enzymatic assays often measure total glutathione first and then use a separate procedure to estimate the oxidized fraction. The difference between total and oxidized amounts provides an indirect estimate of the reduced form.
Acidification lowers pH and slows thiol oxidation during handling. It also helps precipitate proteins that could interfere with detection. Typical choices include metaphosphoric acid and sulfosalicylic acid.
Dissolved oxygen reacts with the thiol group, forming glutathione disulfide. Neutral and alkaline conditions generally increase the oxidation rate. Light, metal ions, and repeated freezing and thawing can also reduce stability.
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.