GSSG is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2025-11-25. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
Commercial glutathione is available in research-grade, food-grade, and supplement-grade forms, and purity specifications differ accordingly. Certificates of analysis commonly report identity by nuclear magnetic resonance or mass spectrometry, purity by HPLC, residual solvents, and heavy metals. Reference standards with assigned purity support calibration, while isotopically labeled glutathione can serve as an internal standard for mass spectrometry. For supplements, label claims may not be independently verified, and regulatory oversight varies by country. Verification often involves third-party testing for identity, potency, and contaminants.
Quantifying glutathione requires distinguishing GSH from GSSG and preventing oxidation during sample preparation. Common approaches include the enzymatic recycling assay, often called the Tietze method, which measures total glutathione after converting GSSG to GSH. HPLC with ultraviolet or fluorescence detection and LC-MS/MS can separate and quantify both forms, sometimes after derivatization of the thiol group. Blood, plasma, and tissue samples differ in matrix and baseline concentrations, so method validation must account for recovery, linearity, and interference. No single assay is universally standard.
Glutathione is most stable as a dry powder stored cool and dry, but its thiol group is readily oxidized in solution. Aqueous preparations at neutral or alkaline pH lose GSH faster because the thiolate form reacts with dissolved oxygen and metal ions. Acidic conditions, chelating agents, and oxygen exclusion can slow oxidation, while repeated freeze-thaw cycles promote degradation. Light exposure and trace metals also contribute to loss. Laboratories typically validate stability for their own matrices because degradation rates depend on pH, temperature, concentration, and container materials.
| 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 |
Commercial glutathione is produced by microbial fermentation or chemical synthesis, then purified. Reduced and oxidized grades are offered separately, with purity specifications often exceeding 98 percent. The compound appears in foods such as fresh fruits, vegetables, and meats, although cooking and processing can lower amounts. Oral, topical, and inhaled forms are discussed in research and consumer contexts, but absorption and tissue delivery remain active areas of study. Regulatory status varies by country and intended use.
Glutathione is a small sulfur-containing peptide built from glutamic acid, cysteine, and glycine. Its distinctive feature is a gamma-glutamyl bond between glutamate's side-chain carboxyl group and cysteine's amino group. This linkage resists ordinary peptidases and helps the molecule remain stable inside cells. The reduced thiol form, often abbreviated GSH, is the dominant intracellular species. The oxidized disulfide dimer, GSSG, forms when two reduced molecules link through their cysteine sulfur atoms. The balance between these forms is a common redox indicator.
In living systems, glutathione occurs in millimolar concentrations in many cell types, while extracellular levels are generally much lower. The liver holds a substantial share of the body's total pool, and the molecule participates in reduction, detoxification, and amino acid transport. It also serves as a cofactor for enzymes such as glutathione peroxidase and glutathione S-transferase. Because the cysteine residue supplies a reactive thiol, glutathione can donate electrons and become oxidized. Cells regenerate reduced glutathione through glutathione reductase using NADPH.
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.
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.
John James Rickard Macleod (6 September 1876 – 16 March 1935), was a Scottish biochemist and physiologist. He devoted his career to diverse topics in physiology and biochemistry, but was chiefly interested in carbohydrate metabolism. He is noted for his role in the discovery and isolation of insulin during his tenure as a lecturer at the University of Toronto, for which he and Frederick Banting received the 1923 Nobel prize in Physiology or Medicine. Awarding the prize to Macleod was controversial at the time, because according to Banting's version of events, Macleod's role in the discovery was negligible. It was not until decades after the events that an independent review acknowledged a far greater role than was attributed to him at first.
The 82nd Airborne division returned to the United States on 3 January 1946 on the RMS Queen Mary. The 82nd initially was staged at Camp Shanks, New York, where they drilled for the coming Victory Parade, to be held in New York City on 12 January 1946. In 1947 the 555th Parachute Infantry Battalion was assigned to the 82nd and was reflagged as the 3d Battalion, 505th Parachute Infantry Regiment, redesignated as the 505th Airborne Infantry Regiment effective 15 December 1947. Instead of being demobilized, the 82nd found a permanent home at Fort Bragg, North Carolina, designated a Regular Army division on 15 November 1948. The 82nd was not sent to the Korean War, as both presidents Truman and Eisenhower chose to keep it in strategic reserve in the event of a Soviet ground attack anywhere in the world. Life in the 82nd in the 1950s and 1960s consisted of intensive training exercises in all environments and locations, including Panama, the Far East, and the continental United States.
=== Nutritional sources of selenium === Dietary selenium comes from meat (including some fish and seafood), some nuts, cereals, mushrooms, and eggs. Brazil nuts are the richest dietary source (although this is soil-dependent since the Brazil nut does not require high levels of the element for its own needs), and the content is high enough that an excessive daily consumption of Brazil nuts may lead to a toxic level even though one a day may be nutritious and, quite helpful in certain health circumstances. In descending order of concentration, high levels of selenium in meat are found in kidney, tuna, crab, and lobster. The US Recommended Dietary Allowance (RDA) of selenium for teenagers and adults is 55 μg/day. Selenium as a dietary supplement is available in many forms, including multi-vitamins/mineral supplements, which typically contain 55 or 70 μg/serving. Selenium-specific supplements typically contain either 100 or 200 μg/serving. In June 2015, the US Food and Drug Administration (FDA) published its final rule establishing a requirement for minimum and maximum levels of selenium in infant formula.
== Valuation == The nature of a drug development project is characterised by high attrition rates, large capital expenditures, and long timelines. This makes the valuation of such projects and companies a challenging task. Not all valuation methods can cope with these particularities. The most commonly used valuation methods are risk-adjusted net present value (rNPV), decision trees, real options, or comparables. The most important value drivers are the cost of capital or discount rate that is used, phase attributes such as duration, success rates, and costs, and the forecasted sales, including cost of goods and marketing and sales expenses. Less objective aspects like quality of the management or novelty of the technology should be reflected in the cash flows estimation.
RNA editing through the addition and deletion of uracil has been found in kinetoplasts from the mitochondria of Trypanosoma brucei. Because this may involve a large fraction of the sites in a gene, it is sometimes called "pan-editing" to distinguish it from topical editing of one or a few sites. Pan-editing starts with the base-pairing of the unedited primary transcript with a guide RNA (gRNA), which contains complementary sequences to the regions around the insertion/deletion points. The newly formed double-stranded region is then enveloped by an editosome, a large multi-protein complex that catalyzes the editing. The editosome opens the transcript at the first mismatched nucleotide and starts inserting uridines. The inserted uridines will base-pair with the guide RNA, and insertion will continue as long as A or G is present in the guide RNA and will stop when a C or U is encountered. The inserted nucleotides cause a frameshift, and result in a translated protein that differs from its gene. The mechanism of the editosome involves an endonucleolytic cut at the mismatch point between the guide RNA and the unedited transcript. The next step is catalyzed by one of the enzymes in the complex, a terminal U-transferase, which adds Us from UTP at the 3' end of the mRNA. The opened ends are held in place by other proteins in the complex. Another enzyme, a U-specific exoribonuclease, removes the unpaired Us. After editing has made mRNA complementary to gRNA, an RNA ligase rejoins the ends of the edited mRNA transcript.
Sources: en.wikipedia.org
Facelift was certified gold by the Recording Industry Association of America (RIAA) for selling 500,000 copies on September 11, 1991, becoming the first album from Seattle's grunge movement to be certified gold. The band continued to hone its audience, opening for such artists as Iggy Pop, Van Halen, Poison, and Extreme. Facelift has since been certified triple-platinum by the RIAA, for shipments of 3,000,000 copies in the US. The concert at the Moore Theatre in Seattle on December 22, 1990, was recorded and released on VHS in mid-1991, as Live Facelift. It features five live songs and three music videos. The home video has been certified gold by the RIAA for sales exceeding 50,000 copies. In early 1991, Alice in Chains landed the opening slot for the Clash of the Titans tour with Anthrax, Megadeth, and Slayer, exposing the band to a wide metal audience but receiving mainly poor reception. Alice in Chains was nominated for a Best Hard Rock Performance Grammy Award in 1992 for "Man in the Box". Following the tour, Alice in Chains entered the studio to record demos for its next album, but ended up recording five acoustic songs instead. While in the studio, drummer Sean Kinney had a dream about "making an EP called Sap". The band decided "not to mess with fate", and on February 4, 1992, Alice in Chains released their second EP, Sap. The EP was released while Nirvana's Nevermind was at the top of the Billboard 200 charts, resulting in a rising popularity of Seattle-based bands, and of the term "grunge music". Sap was certified gold within two weeks.
== Cost == Prices can vary depending on location, but the average cost of cricket flour is around $40 per pound ($88/kg) (4,200 to 4,800 crickets). This price is inflated due to limited commercialization and few processors.
== Awards and honors == 2017, "From Discovery to Precision Medicine: Mass Spectrometry Through the Years and Beyond" at Pittcon 2017, a session focused on the contributions of Robert E. Finnigan 2008, Selected for "Legends of Environmental Chemistry" by American Chemical Society, ACS annual meeting, New York 1999, Instrumentation Hall of Fame (Charter Member) by Pittcon, American Chemical Society and Chemical Heritage Foundation 1994, Selected as a Pioneer in Development of Analytical Instrumentation by Pittsburgh Conference (Pittcon) and American Chemical Society 1980, Distinguished Service in Engineering, College of Engineering, University of Illinois 1975, Distinguished Alumni Award, Electrical and Computer Engineering Department, University of Illinois
74 totally occluded vessels and 47 subtotally occluded vessels were identified in this study, and the presence of total occlusion was the most significant predictor of the existence of collaterals. 63 of 74 (85%) of the "totalled" vessels were accompanied by evidence of collaterals, compared to 8 of 47 (17%) of the subtotalled vessels (p=0.001). Collaterals were completely absent beside arteries with less than 90% stenosis. Totally occluded arteries were found in 29 of 57 patients in the group without Q-wave myocardial infarctions, and all 29 showed collaterals. In comparison, 76% of those who lacked totally occluded arteries showed collaterals (p is less than 0.005). In contrast, all 24 of those 57 patients without Q-wave MI's who did not have collaterals had subtotal stenosis of their diseased vessel. Though smoking, cholesterol levels, and the presence of angina did not differ between the groups, the presence of subendocardial infarction was significantly greater in those with collaterals, suggesting either that subendocardial infarction precipitates the formation of collaterals to an extent comparable to Q-wave infarcts, or that preexisting collaterals prevent subendocardial infarctions from becoming transmural infarctions. Among several Japanese studies utilizing the ergovine-provocative spasm test to simulate ischemia in man and beast, including those of Takeshita and Tada, one by Yamagishi found that spasm in the LAD resulted in (1) ST segment elevation more commonly in those without collaterals than in those with them (8 of 9 vs.
Broad proteomic and transcriptomic profiling has led to innumerable advances in the biomedical space, but the characterization of RNA and protein expression is limited in its ability to inform on the functional characteristics of proteins. Given that transcript and protein expression information leave gaps in knowledge surrounding the effects of post-translational modifications and protein-protein interactions on enzyme activity, and that enzyme activity varies across cell types, disease states, and physiological conditions, specialized tools are required to profile enzyme activity across contexts. Additionally, many identified enzymes have not been sufficiently characterized to yield actionable mechanisms on which to base functional assays. Without a basis for a functional biochemical readout, chemical tools are required to detect drug-protein interactions.
Sources: en.wikipedia.org
According to the 2015–2016 Association of Research Libraries' "Spending by University Research Libraries" report, UA libraries are ranked as the 37th overall university library in North America (out of 114) for university investment. As of 2012, the UA's library system contains over six million print volumes, 1.1 million electronic books, and 74,000 electronic journals. The Main Library, opened in 1976, serves as the library system's reference, periodical, and administrative center; most of the main collections are housed here. The Main Library is on the southeast quadrant of campus near McKale Center and Arizona Stadium. In 2002, the Integrated Learning Center (ILC) was completed as a $20 million, 100,000-square-foot (10,000 m2) computer facility intended for use by incoming students. The ILC features classrooms, auditoriums, a courtyard with vending machines, and an expanded computer lab with several dozen workstations and 3D printing. Computers and 3D printing are available for use by the general public (with some restrictions) as well as by UA students, faculty and staff. The Arizona Health Sciences Library, built in 1996, is on the Health Sciences Center on the north end of campus and on the Phoenix Biomedical Campus, in the Health Sciences Education Building (HSEB). The library serves the Colleges of Medicine, Nursing, Pharmacy, Public Health, and Veterinary Medicine, the University of Arizona Health Network, and is a resource for health professionals and citizens across the state. An important part of the Main Library is the Special Collections library.
=== Legal status === The FDA granted the application for pegcetacoplan orphan drug designation. In October 2021, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Aspaveli, intended for the treatment of adults with paroxysmal nocturnal hemoglobinuria. The applicant for this medicinal product is Swedish Orphan Biovitrum AB (publ). Pegcetacoplan was approved for the treatment of paroxysmal nocturnal hemoglobinuria in the European Union in December 2021. FDA approved Syfovre for the treatment of geographic atrophy secondary to age-related macular degeneration (ARMD) in February 2023. In June 2024, the CHMP recommended the refusal of a marketing authorization for Syfovre, a medicine intended for the treatment of geographic atrophy caused by age-related macular degeneration. The manufacturer requested a re-examination in July 2024. In September 2024, the CHMP continued to refuse a marketing authorization after a re-examination.
Following Charles Darwin's 1859 On the Origin of Species, Fuhlrott and Schaaffhausen argued that Neanderthal 1 represents a primitive lower human form, aligning more closely with non-human apes as well as Negroids, Eskimos, and Aboriginal Australians (which were variably classified as separate species or subspecies of human at the time). The binomial name Homo neanderthalensis was first proposed by William King in a paper read to the 33rd British Science Association in 1863, formally recognising it as distinct from modern humans. However, in 1864 he recommended that Neanderthals and modern humans be classified in different genera as he compared the Neanderthal braincase to that of a chimpanzee and argued that they were "incapable of moral and [theistic] conceptions". The uniqueness of Neanderthal Man met opposition namely from the pathologist Rudolf Virchow, who argued against defining new species based on only a single find. In 1872, Virchow erroneously interpreted Neanderthal characteristics as evidence of senility, disease, and malformation instead of archaicness, which stalled Neanderthal research until the end of the century. By the early 20th century, numerous other Neanderthal discoveries were made, establishing H. neanderthalensis as a legitimate species. At first, many palaeontologists considered Neanderthals to be an intermediary phase between modern humans and more apelike ancestors, as suggested by German anatomist Gustav Albert Schwalbe.
== See also == André Michaux, introduced the ginkgo to North America Bartheletia paradoxa, a unique species of fungus that grows exclusively on Ginkgo leaves Ginkgo Petrified Forest State Park in central Washington, United States Herbalism List of edible seeds
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.
The ratio depends on rapid separation or blocking of GSH before oxidation occurs. GSSG can be formed ex vivo if samples are not processed quickly in cold, acidic conditions. Even small delays can shift the apparent ratio, making standardized protocols essential.