The short version of HPLC fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-12-25. Anything still debated is marked as such rather than presented as settled.
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.
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.
Synthesis occurs in two ATP-dependent steps. The enzyme glutamate-cysteine ligase joins glutamate and cysteine to form gamma-glutamylcysteine, and glutathione synthetase adds glycine. The first step is rate-limiting and is influenced by cysteine availability and feedback inhibition by GSH. Breakdown involves gamma-glutamyl transferase and subsequent peptidases, which release constituent amino acids for reuse. Because turnover differs among tissues, measurements from blood, plasma, and tissues are not directly interchangeable. Research continues to clarify how compartment-specific pools are regulated in health and disease.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. It contains an unusual gamma-glutamyl bond between glutamate and cysteine, which resists cleavage by many peptidases. The reduced form, GSH, carries a thiol group on cysteine and is the dominant intracellular form in most cells. Its structure allows it to participate in redox reactions and to serve as a sulfur donor. The oxidized form, GSSG, consists of two GSH molecules joined by a disulfide bond.
In cells, glutathione helps maintain the reducing environment of the cytosol and supports enzymes that counteract reactive oxygen species. It acts as a cofactor for glutathione peroxidases, which reduce hydrogen peroxide and lipid peroxides, and for glutathione S-transferases, which conjugate electrophiles. The ratio of GSH to GSSG is often used as an indicator of oxidative stress, although the ratio can vary by compartment and cell type. Glutathione also stores cysteine, an amino acid that can be limiting for protein synthesis and antioxidant defense.
| Property | Value | Notes |
|---|---|---|
| Reduced form | GSH | Main intracellular thiol |
| Oxidized form | GSSG | Disulfide dimer of two GSH molecules |
| Common separation method | Reversed-phase HPLC | Often with ion-pairing or derivatization |
| Typical detection | Fluorescence or mass spectrometry | UV detection is also used in some assays |
| Storage of standards | -20 °C or below, desiccated | Limit freeze-thaw and moisture exposure |
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.
Cells synthesize glutathione through two ATP-dependent steps: glutamate-cysteine ligase joins glutamate and cysteine, and glutathione synthetase adds glycine to form the complete tripeptide. Breakdown occurs through gamma-glutamyl transpeptidase and subsequent peptidase reactions, forming the gamma-glutamyl cycle. Within cells, glutathione also forms a disulfide-linked dimer called GSSG when two GSH molecules react. The balance between GSH and GSSG is widely used as an indicator of oxidative conditions, although the ratio can vary by compartment and tissue.
Glutathione supports several cellular processes beyond direct antioxidant action. It serves as a cofactor for glutathione peroxidase and glutathione S-transferase enzymes, which reduce peroxides and conjugate electrophiles, respectively. The molecule also acts as a reservoir of cysteine, an amino acid that can limit protein synthesis and redox signaling. In human nutrition, oral glutathione is sold as a supplement, but how much intact glutathione reaches tissues after ingestion remains an active research question. Clinical claims about supplementation are not uniformly supported by controlled trials.
Glutathione is a small tripeptide built from glutamic acid, cysteine, and glycine. Its peptide bond between glutamate and cysteine involves the gamma-carboxyl group rather than the usual alpha-carboxyl group. This structure gives the molecule a reactive thiol on the cysteine residue. The reduced form, often abbreviated GSH, is the predominant intracellular species in many cell types. Because the thiol can donate electrons, glutathione participates in redox chemistry and in the conjugation of reactive molecules.
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.
Some forms of fabrication tested in outer space are fused deposition printing, which employs 3D printing methods to print using layer-by-layer filament extrusions, semi-solid and direct powder extrusion, effective for bioprinting applications and can be leveraged to process materials found in outer space (silica, magnesium silicate, and calcium phosphate), and photopolymerization, which uses light to print a resin in a layer-by-layer mechanism. These methods are not only used for drug manufacturing but also for biomaterials or medical devices that can load drugs. Finally, methods are used to conduct quality assurance, such as gas chromatography, mass spectrometry, infrared spectroscopy, nuclear magnetic resonance spectroscopy, and other such techniques to identify potential toxins in drug formulations. Advances in handheld, portable, and component miniaturization have developed spectroscopy methods to be more accessible for outer space applications. For example, Raman spectroscopy is a handheld device that can measure drug degradation and drug parameters and efficacy.
=== Production === Polystyrene foams are produced using blowing agents that form bubbles and expand the foam. In expanded polystyrene, these are usually hydrocarbons such as pentane, which may pose a flammability hazard in manufacturing or storage of newly manufactured material, but have relatively mild environmental impact. Extruded polystyrene is usually made with hydrofluorocarbons (HFC-134a), which have global warming potentials of approximately 1000–1300 times that of carbon dioxide. In Europe, where HFC-134a was banned since beginning 2022, XPS is produced using carbon dioxide as blowing agent, achieving an ODP (Ozone depletion potential) of 0 and a GWP (Global warming potential) below 5. Packaging, particularly expanded polystyrene, is a contributor of microplastics from both land and maritime activities.
=== Angiogenesis === MMP9 may play an important role in angiogenesis and neovascularization. For example, MMP9 appears to be involved in the remodeling associated with malignant glioma neovascularization. It is also a key regulator of growth plate formation- both growth plate angiogenesis and the generation of hypertrophic chondrocytes. Knock-out models of MMP9 result in delayed apoptosis, vascularization, and ossification of hypertrophic chondrocytes. Lastly, there is significant evidence that Gelatinase B is required for the recruitment of endothelial stem cells, a critical component of angiogenesis
The vagina is a structure of animals in which the female is internally fertilized, rather than by traumatic insemination used by some invertebrates. Although research on the vagina is especially lacking for different animals, its location, structure and size are documented as varying among species. In therian mammals (placentals and marsupials), the vagina leads from the uterus to the exterior of the female body. Female placentals have two openings in the vulva; these are the urethral opening for the urinary tract and the vaginal opening for the genital tract. Depending on the species, these openings may be within the internal urogenital sinus or on the external vestibule. Female marsupials have two lateral vaginas, which lead to separate uteri, but both open externally through the same orifice; a third canal, which is known as the median vagina, and can be transitory or permanent, is used for birth. The female spotted hyena does not have an external vaginal opening. Instead, the vagina exits through the clitoris, allowing the females to urinate, copulate and give birth through the clitoris. In female canids, the vagina contracts during copulation, forming a copulatory tie. Female cetaceans have vaginal folds that are not found in other mammals. Monotremes, birds, reptiles and amphibians have a cloaca and is the single external opening for the gastrointestinal, urinary, and reproductive tracts. Some of these vertebrates have a part of the oviduct that leads to the cloaca. Chickens have a vaginal aperture that opens from the vertical apex of the cloaca.
Around the elements in the middle of the periodic table, isotopes that are lighter than stable isotopes of the same element tend to decay through electron capture, while isotopes heavier than the stable ones decay by electron emission. Electron capture happens most often in the heavier neutron-deficient elements where the mass change is smallest and positron emission is not always possible. When the loss of mass in a nuclear reaction is greater than zero but less than 2mec2 the process cannot occur by positron emission, but occurs spontaneously for electron capture.
Sources: en.wikipedia.org
Biopharmaceuticals may be produced from microbial cells (e.g., recombinant E. coli or yeast cultures), mammalian cell lines (see Cell culture) and plant cell cultures (see Plant tissue culture) and moss plants in bioreactors of various configurations, including photo-bioreactors. Important issues of concern are cost of production (low-volume, high-purity products are desirable) and microbial contamination (by bacteria, viruses, mycoplasma). Alternative platforms of production which are being tested include whole plants (plant-made pharmaceuticals).
Several aircraft and helicopters were damaged in a storm on 1 July 2017 that struck the air force's main base at N'Djamena International Airport. The severity of the storm was amplified by the use of fabric hangar coverings. Losses or damaged equipment included three helicopters, a PC-12, a MiG-29 fighter, and two Su-25 attack planes. The force shared a base with French forces at N'Djamena International Airport until January 2025 when the French withdrew.
== Appearance and behaviour == Laboratory mice have retained many of the physical and behavioural characteristics of house mice; however, due to many generations of artificial selection, some of these characteristics now vary markedly. Due to the large number of strains of laboratory mice, it is impractical to comprehensively describe the appearance and behaviour of all of them; however, they are described below for two of the most commonly used strains.
=== Performing arts and cinema === Moscow is the heart of Russian performing arts, including ballet and cinema: 68 museums, 103 theaters, 132 cinemas, and 24 concert halls. Among Moscow's theaters and ballet studios are the Bolshoi Theatre, the Malyi Theatre, the Vakhtangov Theatre, and the Moscow Art Theatre. The Moscow International Performance Arts Center, opened in 2003—also called the Moscow International House of Music—is known for classical music performances. This center contains Russia's largest organ, which is installed in Svetlanov Hall. In addition, Moscow contains two large circuses: the Moscow State Circus and the Moscow Circus on Tsvetnoy Boulevard (also called Nikulin's Circus, after Yuri Nikulin). The Mosfilm studio was at the heart of many classic films, as it has been responsible for both artistic and mainstream productions. However, despite the ongoing participation and reputation of internationally known Russian filmmakers, previously prolific domestic studios have become less active. The Salut cinema screens rare and historical films, and films from the Museum of Cinema are regularly shown. International film festivals are held in Moscow, including the Moscow International Film Festival, Stalker (focusing on human rights), Artdocfest (focusing on documentaries), and the Moscow Jewish Film Festival.
== Pathology == The interaction of GPX4 with the autophagic degradation pathway further modulates cell's response to oxidative stress. Impaired GPX4 function plays a role in tumorigenesis, neurodegeneration, infertility, inflammation, immune disorders, and ischemia-reperfusion injury. Additionally, the R152H mutation in GPX4 is involved in the development of Sedaghatian-type spinal metaphyseal dysplasia, a rare and fatal disease in newborn babies.
Sources: en.wikipedia.org
A team led by chemist Gary Rasmusson and biologist Jerry Brooks developed potential 5α-reductase inhibitors based on transition-state inhibitors, using an iterative process of molecular design, testing, and redesign. In 1992, finasteride (5 mg) was approved by the US Food and Drug Administration (FDA) for treatment of BPH, which Merck marketed under the brand name Proscar. Rasmusson and Brooks were awarded IPO's "Inventor of the Year" award in 1993 for their work on finasteride. In 1997, Merck was successful in obtaining FDA approval for a second indication of finasteride (1 mg) for treatment of male pattern hair loss, which was marketed under the brand name Propecia. It was the first 5α-reductase inhibitor to be introduced and was followed by dutasteride in 2001. The first study of finasteride in the treatment of hirsutism in women was published in 1994.
Because a breast implant is a Class III medical device of limited product-life, the principal rupture-rate factors are its age and design; nonetheless, a breast implant device can retain its mechanical integrity for decades in a woman's body. When a saline breast implant ruptures, leaks, and empties, it quickly deflates, and thus can be readily explanted (surgically removed). In some cases, saline implant rupture can result in an infection due to bacteria or mold that had been within the implant, though this is uncommon. The follow-up report, Natrelle Saline-filled Breast Implants: a Prospective 10-year Study (2009) indicated rupture-deflation rates of 3–5 per cent at 3-years post-implantation, and 7–10 per cent rupture-deflation rates at 10-years post-implantation. In a study of his 4761 augmentation mammaplasty patients, Eisenberg reported that overfilling saline breast implants 10-13% significantly reduced the rupture-deflation rate to 1.83% at 8-years post-implantation.
=== The Finke era with ten Bundesliga seasons (1991–2007) === SC Freiburg were promoted to the 2. Bundesliga in 1978–79, which they would compete in for a decade-and-a-half before making the breakthrough to the top-flight Bundesliga in 1993–94 under the management of Volker Finke. In their first Bundesliga season, Freiburg narrowly avoided relegation. They made a third-place finish in their second season at the top level, just three points behind champions Borussia Dortmund. It was at this time that they were first nicknamed Breisgau-Brasilianer (literally Breisgau-Brazilians), due to their attractive style of play. The club reached the UEFA Cup in 1995, where they were knocked out in the first round by Slavia Prague. In 2001 they reached the UEFA Cup for a second time, where they were knocked out by Feyenoord. Freiburg's first Bundesliga relegation was in 1997 after they finished in 17th position. While they have been relegated four times since first making the Bundesliga, they have thrice won immediate promotion back to the top league. It was the first time since 1992 that Freiburg played in the 2. Bundesliga for two consecutive seasons. Freiburg finished the 2006–07 season in fourth place in the 2. Bundesliga, missing out on the third automatic-promotion spot on goal difference to MSV Duisburg, although they won 12 of their last 16 league games. They were knocked out of the DFB-Pokal in the second round by VfL Wolfsburg on 24 October 2006. On 20 May 2007, Volker Finke resigned as the club's coach after 16 years in the job.
The Phoenicians also made a deep blue-coloured dye, sometimes referred to as royal blue or hyacinth purple, which was made from a closely related species of marine snail. The Phoenicians established an ancillary production facility on the Iles Purpuraires at Mogador, in Morocco. The sea snail harvested at this western Moroccan dye production facility was Hexaplex trunculus, also known by the older name Murex trunculus. This second species of dye murex is found today on the Mediterranean and Atlantic coasts of Europe and Africa (Spain, Portugal, Morocco).
Sources: en.wikipedia.org
Common methods include enzymatic recycling assays, liquid chromatography, and mass spectrometry. Many protocols separate reduced glutathione from its oxidized disulfide form before detection.
The ratio compares reduced glutathione with its oxidized dimer. It is used as an indicator of redox status, although the value depends strongly on sample handling and analytical method.
Glutathione can oxidize quickly after a sample is collected. Acidification, cooling, and chelators are often used to reduce artifactual changes before analysis.
GSH is the reduced form with a free thiol group, while GSSG is the oxidized disulfide-linked dimer. Most assays distinguish the two because their balance reflects redox conditions. The names are not interchangeable.