LC-MS/MS comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-06-27. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Typical assay | HPLC-UV or LC-MS/MS | Derivatization may improve detection |
| Storage temperature | -20 °C or below | Keep desiccated and protected from light |
| Appearance | White to off-white crystalline powder | Reduced form |
| Solubility | Freely soluble in water | Insoluble in lipids and nonpolar solvents |
| Common synonyms | L-Glutathione; GSH | GSH denotes reduced form |
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.
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.
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.
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.
Measuring glutathione requires attention to oxidation during sample handling, because GSH in biological samples can convert to GSSG or form mixed disulfides with proteins after collection. Acidic extraction, rapid cooling, and chelating agents are commonly used to limit such changes. Analytical methods usually distinguish free reduced glutathione, total glutathione, and protein-bound forms. Because these forms have different stability and reactivity, reported values depend heavily on the preparation protocol. No single preparation is universally suitable for every biological matrix or analytical goal.
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.
Common analytical approaches include enzymatic recycling assays, high-performance liquid chromatography, and mass spectrometry. The enzymatic recycling assay uses glutathione reductase and a colorimetric or fluorometric reagent to amplify signal, which gives good sensitivity for total glutathione. Chromatographic methods can separate GSH from GSSG and related thiols, while mass spectrometry offers structural confirmation and multiplexing. Each approach has different requirements for calibration, internal standards, and validation. No single method captures every form of glutathione in every matrix.
Storage recommendations for glutathione reagents usually specify a cool, dry, dark environment because the thiol oxidizes in air and light. Solid material is often kept desiccated at low temperature, while solutions are prepared fresh or stored frozen in aliquots. Repeated freeze-thaw cycles can accelerate degradation, and metal ions can catalyze oxidation. Quality control may include purity assays, water content, and identity confirmation. Stability limits are method-specific, so a stated shelf life applies only to defined conditions and packaging.
Laboratory measurement of glutathione requires attention to oxidation before analysis. Blood, tissue, or cell samples can lose reduced glutathione as it converts to GSSG or forms mixed disulfides with proteins. Acid extraction, rapid freezing, and thiol-blocking reagents are common strategies to preserve the original distribution. Reported concentrations therefore depend on collection protocol, extraction method, and the time between sampling and analysis. Comparisons across studies are most reliable when these pre-analytical variables are described.
A drone attack struck industrial facilities in Yelabuga and Nizhnekamsk in the Russian republic of Tatarstan. The drones hit the Yelabuga drone factory, causing "significant damage", according to Ukrainian officials. A local Russian official denied any damage to the factory. Russian media reported a nearby workers' dormitory was damaged, injuring twelve college students, including five minors, who were employed at the drone manufactory. Other drones struck the Tatneft oil refinery in Nizhnekamsk, causing a fire that did not cause "critical damage". A Ukrainian-made light aircraft, believed to be an Aeroprakt A-22 Foxbat, was converted into a one-way drone. Another drone attack later that day damaged several buildings in Kursk. Ukrainian military intelligence (HUR) said it had blown up an electricity substation in Sevastopol, causing blackouts in the city. Two people were killed in Russian attacks in Kharkiv and Kherson Oblasts. Eighteen people were injured in a missile attack on Dnipro. Russian president Vladimir Putin appointed vice-admiral Sergei Pinchuk as commander of the Russian Black Sea Fleet. Ukrainian president Volodymyr Zelenskyy signed a law lowering the age of conscription in Ukraine from 27 years to 25. The Register of Damage Caused by the Aggression of the Russian Federation against Ukraine (RD4U), an online registry for Ukrainians to submit claims for damage caused by the Russian invasion, was officially opened, with at least 100 claims submitted in the first hours.
Plants are a rich source of ribosomally-synthesised and post-translationally modified cyclic peptides. Among these, the cyclotides are gene-coded products generated via processing of a larger precursor protein. The gene for the first such precursor is Oak1 (Oldenlandia affinis kalata clone number 1), which was shown to be responsible for the synthesis of kalata B1. The generic configuration of the precursor protein consists of an endoplasmic reticulum signal sequence, a non-conserved pro-region, a highly conserved region known as the N-terminal repeat (NTR), the mature cyclotide domain and finally a short hydrophobic C-terminal tail. The cyclotide domain may contain either one cyclotide sequence, as in the case of Oak1, or multiple copies separated by additional NTR sequences as seen for Oak2 and Oak4. In precursor proteins containing multiple cyclotide domains these can either be all identical sequences, as is the case for Oak4, or they can be different cyclotides as in Oak2 which contains sequences corresponding to kalata B3 and B6. Recently, the enzyme responsible for the backbone cyclization of cyclotides has been isolated from the medicinal plant Clitoria ternatea. This enzyme was named butelase 1 in accordance to the local name of the plant (Bunga Telang Ligase). Butelase 1 has been shown to cyclize the linear precursor of kalata B1 with >95% yield at a remarkable rate of 5.42×105 M−1 s−1.
The first attempt to give scientific basis for the cause of this disease was by a ship's surgeon in the Royal Navy, James Lind. While at sea in May 1747, Lind provided some crew members with two oranges and one lemon per day, in addition to normal rations, while others continued on cider, vinegar, sulfuric acid or seawater, along with their normal rations, in one of the world's first controlled experiments. The results showed that citrus fruits prevented the disease. Lind published his work in 1753 in his Treatise on the Scurvy. Fresh fruit was expensive to keep on board, whereas boiling it down to juice allowed easy storage, but destroyed the vitamin (especially if it was boiled in copper kettles). It was 1796 before the British navy adopted lemon juice as standard issue at sea. In 1845, ships in the West Indies were provided with lime juice instead, and in 1860 lime juice was used throughout the Royal Navy, giving rise to the American use of the nickname "limey" for the British. Captain James Cook had previously demonstrated the advantages of carrying "Sour krout" on board by taking his crew on a 1772–75 Pacific Ocean voyage without losing any of his men to scurvy. For his report on his methods the British Royal Society awarded him the Copley Medal in 1776. The name antiscorbutic was used in the eighteenth and nineteenth centuries for foods known to prevent scurvy. These foods included lemons, limes, oranges, sauerkraut, cabbage, malt, and portable soup.
Generalized depression: Generalized depression is seen in the early stages of glaucoma and many other conditions. Mild constriction of the central and peripheral visual field due to isopter contraction comes under generalized depression. If all the isopters show similar depression to the same point, it is then called a contraction of the visual field. Relative paracentral scotomas are the areas where smaller and dimmer targets are not visualized by the patient. Larger and brighter targets can be seen. Small paracentral depressions, mainly superonasal are seen in normal tension glaucoma (NTG). The generalized depression of the entire field may be seen in cataract also. Baring of blind spot: "Baring of blind spot" means exclusion of blind spot from the central field due to the inward curve of the outer boundary of 30° central field. It is only an early non-specific visual field change, without much diagnostic value in glaucoma. Small wing-shaped Paracentral scotoma: Small wing-shaped Paracentral scotoma within Bjerrum's area is the earliest clinically significant field defect seen in glaucoma. It may also be associated with nasal steps. Scotoma may be seen above or below the blind spot. Siedel's sickle-shaped scotoma: Paracentral scotoma joins with the blind spot to form the Seidel sign. Arcuate or Bjerrum's scotoma: It is formed at later stages of glaucoma by extension of Seidel's scotoma in an area either above or below the fixation point to reach the horizontal line. Peripheral breakthrough may occur due to damage to nerve fibers.
Berkelium(IV) fluoride (BkF4) is a yellow-green ionic solid and is isotypic with uranium tetrafluoride or zirconium tetrafluoride. Berkelium(III) fluoride (BkF3) is also a yellow-green solid, but it has two crystalline structures. The most stable phase at low temperatures is isotypic with yttrium(III) fluoride, while upon heating to between 350 and 600 °C, it transforms to the structure found in lanthanum trifluoride. Visible amounts of berkelium(III) chloride (BkCl3) were first isolated and characterized in 1962, and weighed only 3 billionths of a gram. It can be prepared by introducing hydrogen chloride vapors into an evacuated quartz tube containing berkelium oxide at a temperature about 500 °C. This green solid has a melting point of 600 °C, and is isotypic with uranium(III) chloride. Upon heating to nearly melting point, BkCl3 converts into an orthorhombic phase. Two forms of berkelium(III) bromide are known: one with berkelium having coordination 6, and one with coordination 8. The latter is less stable and transforms to the former phase upon heating to about 350 °C. An important property of radioactive solids has been studied on these two crystal forms: the structure of fresh and aged 249BkBr3 samples was probed by X-ray diffraction over a period longer than 3 years, so that various fractions of berkelium-249 had beta decayed to californium-249. No change in structure was observed upon the 249BkBr3—249CfBr3 transformation. However, other differences were noted for 249BkBr3 and 249CfBr3.
Sources: en.wikipedia.org
"Neats" hope that intelligent behaviour is described using simple, elegant principles (such as logic or optimisation). "Scruffies" expect that it necessarily requires solving a large number of unrelated problems. Neats defend their programs with theoretical rigour, scruffies rely mainly on incremental testing to see if they work. This issue was actively discussed in the 1970s and 1980s. The rise of deep learning may represent a shift toward the scruffies.
Lyubimov & Sablin (2026) report pathological modifications in a mandible of Canis etruscus from the Pleistocene strata from the Muhkai 2 locality (Dagestan, Russia) identified as a fully healed displaced mandibular fracture, and interpret the survival of the studied individual as a likely evidence of sociality and conspecific care in C. etruscus. Blázquez-Orta et al. (2026) study the fossil material of Early and Middle Pleistocene canids from the Atapuerca Mountains (Spain), interpret the morphology of the studied fossils as consistent with a gradual transition from Canis mosbachensis to the wolf, and determine the observed morphological changes to coincide with a climatic shift. Evidence from the study of tooth wear in late Pleistocene wolves from Britain, indicative of dietary shifts related to climate and environmental changes, is presented by Burtt et al. (2026). Micucci et al. (2026) compare the lengths and widths of carnassial teeth and overall body mass of Pleistocene grey wolves from eastern Beringia and recent Canadian individuals, find no evidence of significant body size differences between Pleistocene Yukon wolves and modern Canadian ones when accounting for sample size differences, and interpret Pleistocene Yukon wolves and modern Canadian wolves as belonging to the same ecotype, different from larger Pleistocene wolves from Alaska and Siberia.
=== Extraction === Oil extraction is simply the removal of oil from the reservoir (oil pool). There are many methods of extracting the oil from the reservoirs for example; mechanical shaking, water-in-oil emulsion, and specialty chemicals called demulsifiers that separate the oil from water. Oil extraction is costly and often environmentally damaging. Offshore exploration and extraction of oil disturb the surrounding marine environment.
=== Far-infrared === The first FTIR spectrometers were developed for far-infrared range. The reason for this has to do with the mechanical tolerance needed for good optical performance, which is related to the wavelength of the light being used. For the relatively long wavelengths of the far infrared, ~10 μm tolerances are adequate, whereas for the rock-salt region tolerances have to be better than 1 μm. A typical instrument was the cube interferometer developed at the NPL and marketed by Grubb Parsons. It used a stepper motor to drive the moving mirror, recording the detector response after each step was completed.
Regular production batches of 238PuO2 particles precipitated as a hydroxide were used to show that large production batches could be effectively 16O2-exchanged on a routine basis. High-fired 238PuO2 microspheres were successfully 16O2-exchanged showing that an exchange will take place regardless of the previous heat treatment history of the 238PuO2. This lowering of the neutron emission rate of PuO2 containing normal oxygen by a factor of five was discovered during the cardiac pacemaker research at Mound Laboratory in 1966, due in part to the Mound Laboratory's experience with production of stable isotopes beginning in 1960. For production of the large heat sources the shielding required would have been prohibitive without this process. Unlike the other three isotopes discussed in this section, 238Pu must be specifically synthesized and is not abundant as a nuclear waste product. At present only Russia has maintained high-volume production, while in the US, no more than 50 g (1.8 oz) were produced in total between 2013 and 2018. The US agencies involved desire to begin the production of the material at a rate of 300 to 400 grams (11 to 14 oz) per year. If this plan is funded, the goal would be to set up automation and scale-up processes in order to produce an average of 1.5 kg (3.3 lb) per year by 2025.
Sources: en.wikipedia.org
Common methods include spectrophotometric enzyme cycling assays, HPLC with UV or fluorescence detection, and LC-MS/MS. Detection often requires derivatization because glutathione lacks a strong chromophore. Method choice depends on the sample type and the required sensitivity.
Yes, especially in solution or when exposed to oxygen, light, and heat. The reduced form can oxidize to GSSG or form disulfides with other thiols. Powdered material stored cool and dry is generally more stable than aqueous preparations.
Purity refers to the proportion of the intended compound in a sample, often determined by chromatography. A high purity value does not necessarily indicate a specific oxidation state. Buyers may also need information about GSSG content, water, and residual solvents.
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.