Everything below concerns LC-MS/MS. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-08-29. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. It occurs in nearly all living cells, with highest concentrations in liver, kidney, and red blood cells, and exists in reduced (GSH) and oxidized disulfide (GSSG) forms. The cysteine thiol group enables reversible oxidation and reduction reactions. This property makes glutathione a central participant in cellular redox balance. The balance between these forms is often used as an indicator of oxidative stress.
Glutathione synthesis proceeds in two ATP-dependent steps catalyzed by glutamate-cysteine ligase and glutathione synthetase. The first step joins glutamate and cysteine to form gamma-glutamylcysteine and is generally rate-limiting. The second step adds glycine to complete the tripeptide. Cysteine availability, feedback inhibition by glutathione, and oxidative conditions influence flux through this pathway. The pathway is conserved across many organisms, and degradation by gamma-glutamyl transpeptidase and related peptidases recycles amino acids for new synthesis.
| 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 |
Several techniques are used for quantification. Enzymatic recycling assays rely on glutathione reductase and a colorimetric or fluorescent readout, offering sensitivity for total glutathione. High-performance liquid chromatography can separate GSH from GSSG and other thiols, often with UV, fluorescence, or electrochemical detection. Mass spectrometry provides structural confirmation and can quantify low-abundance species when paired with separation. Each approach has trade-offs in specificity, throughput, and equipment requirements, so method selection depends on the research question and available instrumentation.
Stability depends on pH, temperature, oxygen exposure, and trace metals. Aqueous solutions of reduced glutathione are susceptible to oxidation, especially when neutral or alkaline and exposed to air. Transition metal ions can catalyze thiol oxidation, so chelators and inert atmospheres are sometimes used in research settings. Standards are typically stored cold and desiccated, with limited freeze-thaw cycles. Questions remain about how closely in vitro stability data reflect the behavior of glutathione within intact cells and tissues.
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.
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.
== Medical uses == Albiglutide was used for the treatment of type 2 diabetes in adults. It can be used alone (if metformin therapy is ineffective or not tolerated) or in combination with other antidiabetic drugs, including insulins. According to a 2015 analysis, albiglutide is less effective than other GLP-1 agonists for lowering glycated hemoglobin (HbA1c, an indicator for long-term blood glucose control) and weight loss. It also seems to have fewer side effects than most other drugs of this class, except for reactions at the injection site which are more common under albiglutide than, for example, under liraglutide.
Edelman, Under Secretary of Defense for Policy, described the shelling of the Georgian villages in hearing of the United States Senate Committee on Armed Services and said that Russian peacekeepers neglected their obligation to curb artillery fire and that Georgian military began to quell artillery sites in South Ossetia on the night of 7 August. Edelman said that although Russian officials had claimed that Russia's goal was defense of Russian citizens and peacekeepers, "What became clear is there never seemed to be a limit to Russia's operational – nor strategic – aims." Edelman said that the Russian invasion was pre-planned. According to Edelman, although Putin had blamed the United States for arming Georgia, the United States had never intended for the Georgian forces to oppose Russia. Edelman further stated, "Russia was clearly adding to tension in order to provoke a Georgian response." Edelman said that the first modern Russian invasion of foreign country "sends a chilling message" about new Russian foreign policy. In September 2008, Dana Rohrabacher (a senior Republican member of the United States House of Representatives) argued at a United States House Committee on Foreign Affairs meeting that Georgia started the fighting on August 7, citing alleged unnamed intelligence reports. Telegraph noted the Russian media paid much attention to Rohrabacher's remarks. In September 2008, Senator Hillary Clinton proposed to create a U.S. commission to study the war.
=== Endoscopy === After Edlich learned about endoscopes in Asia, he received an endoscope for gastroscopic visualization of the patient's stomach. As a surgical resident, Edlich was the first physician to do a gastroscopy at the University of Minnesota Medical Center. Edlich's picture was featured on the cover of Postgraduate Medicine, the Journal of Applied Medicine, in November 1968. His experiences with gastroscopy led to the first minimally invasive surgical procedure at the University of Minnesota Hospital, an endoscopic gastrostomy. Edlich soon realized the limitations of the thick, narrow-diameter latex Ewald tubes that were being used to evacuate blood clots from the patient's stomach before endoscopic examination. Edlich devised a thin-walled, transparent, plastic tube for evacuation of blood clots from a patient's stomach.
Sources: en.wikipedia.org
=== A Beautiful Mind === In 1959, the 1994 Nobel Prize winner in Economics, John Nash, was diagnosed with schizophrenia and was initially treated at McLean Hospital. When he relapsed, he was admitted to Trenton Psychiatric Hospital in New Jersey. His associates at Princeton University pleaded with the hospital director to have Nash admitted to the insulin coma unit, recognizing that it was better staffed than other hospital units. He responded to treatment and was subsequently medicated with neuroleptics. Nash's life story was presented in the film A Beautiful Mind, which accurately portrayed the seizures associated with his treatments. In a review of the Nash history, Fink ascribed the success of coma treatments to the 10% of associated seizures, noting that physicians often augmented the comas by convulsions induced by ECT. He envisioned insulin coma treatment as a weak form of convulsive therapy.
=== OB3b === Methanobactin OB3b is a commonly studied methanobactin. It has a molecular weight of 1154Da when metal free. OB3b is composed of 9 amino acid residues with two oxazolone rings, which take part in binding to copper ions. The oxazalone rings are susceptible to cleavage under low pH conditions, which releases any metal ion bound to the rings. Copper is bound and reduced at a tetradentate binding site composed of 2 oxazolone rings and 2 modified enethiol groups. In particular, the origin and function of these oxazolone rings in methanobactin OB3b has been the subject of research, since these domains appear unique. In 2010, it was suggested that mb OB3b is derived from a small, ribsomally-produced peptide precursor with the sequence of L-C-G-S-C-Y-P-C-S-C-M. Functional mbOB3b is composed of (isobutyl group)-(Oxazolone ring A)-G-S-C-Y-(Oxazolone ring B)-S-M. (Note that some specimens of mBOB3b are found without the C-terminal methionine and appear fully functional.) It has been argued that the chromophoric rings of this particular species of methanobactin enable mbOB3b to bind and reduce other metals. For example, mbOB3b can reduce Ag(I) to Ag(0), Au(III) to Au(0), Cr(VI) to Cr(III), and Hg(II) to Hg(I); it is also able to bind Co(II), Zn (II), Mn(II), Pb(II), and U(IV). Because of this, it is possible that methanobactin may have several medical and environmental applications as a metal chelator and reducing agent. The mechanism of metal reduction is currently undetermined.
With the death of Stalin and ensuing de-Stalinisation, Marxism–Leninism underwent revisions and adaptations such as Guevarism, Titoism, Ho Chi Minh Thought, Hoxhaism, and Maoism, with the latter two constituting anti-revisionist Marxism–Leninism. These adaptations caused splits between communist states, resulting in the Tito–Stalin split, the Sino-Soviet split, and the Sino-Albanian split. As the Cold War concluded with the demise of much of the socialist world, many surviving communist states reformed their economies and embraced market socialism. Complementing this economic shift, the Communist Party of China developed Maoism into Deng Xiaoping Theory. Today this comprises part of China's governing ideology, with the latest developments including Xi Jinping Thought. Meanwhile, the Communist Party of Peru developed Maoism into Marxism–Leninism–Maoism. The latest developments to Marxism–Leninism–Maoism include Gonzaloism, Maoism-Third Worldism, National Democracy, and Prachanda Path. Ongoing Marxist–Leninist (Maoist) insurgencies include those waged in the Philippines, India, and Turkey. The Nepalese Civil War, fought by Marxist–Leninist–Maoists, ended in their victory in 2006. Criticism of Marxism–Leninism overlaps with criticism of communist party rule and focuses on the actions and policies of Marxist–Leninist leaders, notably Stalin and Mao Zedong. Communist states have been marked by centralised state control by the communist party, political repression, state atheism, collectivisation and labour camps.
=== Ovulation === NGF is abundant in seminal plasma. Recent studies have found that it induces ovulation in some mammals e.g. "induced" ovulators, such as llamas. Surprisingly, research showed that these induced animals will also ovulate when semen from on-schedule or "spontaneous" ovulators, such as cattle is used. Its significance in humans is unknown. It was previously dubbed ovulation-inducing factor (OIF) in semen before it was identified as beta-NGF in 2012.
Sources: en.wikipedia.org
Initially, pyruvate and thiamine pyrophosphate (TPP or vitamin B1) are bound by pyruvate dehydrogenase subunits. The thiazolium ring of TPP is in a zwitterionic form, and the anionic C2 carbon performs a nucleophilic attack on the C2 (ketone) carbonyl of pyruvate. The resulting intermediate undergoes decarboxylation to produce an acyl anion equivalent (see cyanohydrin or aldehyde-dithiane umpolung chemistry, as well as benzoin condensation). This anion attacks S1 of an oxidized lipoate species that is attached to a lysine residue. In a ring-opening SN2-like mechanism, S2 is displaced as a sulfide or sulfhydryl moiety. Subsequent collapse of the tetrahedral intermediate ejects thiazole, releasing the TPP cofactor and generating a thioacetate on S1 of lipoate. The E1-catalyzed process is the rate-limiting step of the whole pyruvate dehydrogenase complex.
Aminoglycoside is a medicinal and bacteriologic category of traditional Gram-negative antibacterial medications that inhibit protein synthesis and contain as a portion of the molecule an amino group-containing sugar. The term can also refer more generally to any organic molecule that contains amino sugar substructures. Aminoglycoside antibiotics display bactericidal activity against Gram-negative aerobes and some anaerobic bacilli where resistance has not yet arisen but generally not against Gram-positive and anaerobic Gram-negative bacteria. Streptomycin is the first-in-class aminoglycoside antibiotic. It is derived from Streptomyces griseus and is the earliest modern agent used against tuberculosis. Streptomycin lacks the common 2-deoxystreptamine moiety (image right, below) present in most other members of this class. Other examples of aminoglycosides include the deoxystreptamine-containing agents kanamycin, tobramycin, gentamicin, and neomycin (see below).
The fundamental process in photoionization is the absorption of a high-energy photon by the molecule and subsequent ejection of an electron. In direct APPI, this process occurs for the analyte molecule, forming the molecular radical cation M•+. The analyte radical cation can be detected as M•+ or it can react with surrounding molecules and be detected as another ion. The most common reaction is the abstraction of a hydrogen atom from the abundant solvent to form the stable [M+H]+ cation, which is usually the observed ion. In dopant-APPI (or photoionization-induced APCI), a quantity of photoionizable molecules (e.g., toluene or acetone) is introduced into the sample stream to create a source of charge carriers. Use of a photoionizable solvent can also achieve the same effect. The dopant or solvent ions can then react with neutral analyte molecules via proton transfer or charge exchange reactions. The above table simplifies the dopant process. In fact, there may be extensive ion-molecule chemistry between dopant and solvent before the analyte becomes ionized. APPI can also produce negative ions by creating a high abundance of thermal electrons from dopant or solvent ionization or by photons striking metal surfaces in the ionization source. The cascade of reactions that can lead to M− or dissociative negative ions [M-X]− often involve O2 as an electron charge carrier. Examples of negative ionization mechanisms include: Direct or dopant-assisted negative ion APPI
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 form, while GSSG is the disulfide-linked oxidized dimer. The GSH:GSSG ratio is used as a redox indicator, though the ratio can vary with sample handling and cell type.