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 2025-11-04. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C10H17N3O6S | Reduced glutathione (GSH) |
| Molar mass | 307.32 g/mol | Oxidized dimer GSSG is 612.63 g/mol |
| Appearance | White to off-white crystalline powder | Typical purified solid |
| Solubility | Freely soluble in water; practically insoluble in ethanol | Polarity reflects multiple ionizable groups |
| Common synonyms | GSH; L-glutathione; γ-glutamylcysteinylglycine | 'Reduced' distinguishes it from GSSG |
A study skin is a taxidermic zoological specimen prepared in a minimalistic fashion that is concerned only with preserving the animal's skin, not the shape of the animal's body. As the name implies, study skins are used for scientific study (research), and are housed mainly by museums. A study skin's sole purpose is to preserve data, not to replicate an animal in a lifelike state. Museums keep large collections of study skins in order to conduct comparisons of physical characteristics to other study skins of the same species. Study skins are also kept because DNA can be extracted from them when needed at any point in time. A study skin's preparation is extremely basic. After the animal is skinned, fat is methodically scraped off the underside of the hide. The underside of the hide is then rubbed with borax or cedar dust to help it dry faster. The animal is then stuffed with cotton and sewn up. Mammals are laid flat on their belly. Birds are prepared lying on their back. Study skins are dried in these positions to keep the end product as slender and streamlined as possible so large numbers of specimens can be stored side-by-side in flat file drawers, while occupying a minimum amount of space. Since study skins are not prepared with aesthetics in mind they do not have imitation eyes like other taxidermy, and their cotton filling is visible in their eye openings.
Sodium thiopental is a member of the barbiturate class of drugs, which are relatively non-selective compounds that bind to an entire superfamily of ligand-gated ion channels, of which the GABAA receptor channel is one of several representatives. This superfamily of ion channels includes the neuronal nicotinic acetylcholine receptor (nAChR), the 5-HT3 receptor, the glycine receptor and others. Surprisingly, while GABAA receptor currents are increased by barbiturates (and other general anesthetics), ligand-gated ion channels that are predominantly permeable for cationic ions are blocked by these compounds. For example, neuronal nAChR are blocked by clinically relevant anesthetic concentrations of both sodium thiopental and pentobarbital. Such findings implicate (non-GABAergic) ligand-gated ion channels, e.g. the neuronal nAChR, in mediating some of the (side) effects of barbiturates. The GABAA receptor is an inhibitory channel that decreases neuronal activity, and barbiturates enhance the inhibitory action of the GABAA receptor.
The poor taste and lack of sugar in modern garden and commercial tomato varieties resulted from breeding tomatoes to ripen uniformly red. This change occurred after the discovery of a mutant "u" phenotype in the mid-20th century, so named because the fruits ripened uniformly. This was widely cross-bred to produce red fruit without the typical green ring around the stem on un-crossbred varieties. Before this, most tomatoes produced more sugar during ripening, and were sweeter and more flavorful. 10–20% of the total carbon fixed in the fruit can be produced by photosynthesis in the developing fruit of the normal U phenotype. The u mutation encodes a factor that produces defective chloroplasts with lower density in developing fruit, making them a lighter green, and reducing sugar in the resulting ripe fruit by 10–15%. Perhaps more importantly, the fruit chloroplasts are remodelled during ripening into chlorophyll-free chromoplasts that synthesize and accumulate the carotenoids lycopene, β-carotene, and other metabolites that are sensory and nutritional assets of the ripe fruit. The potent chloroplasts in the dark-green shoulders of the "U" phenotype are beneficial here, but have the disadvantage of leaving green shoulders near the stems of the ripe fruit, and even cracked yellow shoulders. This is apparently because of oxidative stress due to overload of the photosynthetic chain in direct sunlight at high temperatures. Hence, genetic design of a commercial variety that combines the advantages of types "u" and "U" requires fine-tuning, but may be feasible.
=== Locations === Stumptown operates five cafes in Portland. They are located on SE 45th & Division St., SE 34th & Belmont, downtown at SW 3rd & Ash St., inside the Ace Hotel at 1022 SW Stark Street, and at the Portland International Airport. The company also owns a roasting facility and a retail annex inside their headquarters at 100 SE Salmon St. The original location on SE Division was previously a hair salon called "The Hair Bender," whose name Stumptown adopted for one of their signature espresso blends. In November 2007, Stumptown opened two cafes in Seattle. In September 2009, the company also launched a cafe in New York's Ace Hotel. A temporary "pop-up" location appeared in Amsterdam's De Pijp neighborhood in May 2010. Opened by Sorenson, he claimed it was never intended to be permanent and closed its doors that same year. In 2013, Stumptown opened a second New York City café and a café/roaster in Los Angeles. Additional cafes have also opened in Chicago and New Orleans. Stumptown opened their third New York cafe in a historic Brooklyn firehouse in the summer of 2018. A location at the Portland International Airport opened in 2024.
Sources: en.wikipedia.org
The Gibbs phase rule states that, under most thermodynamic conditions (fixed temperature, pressure, chemical potential, and other intensive thermodynamic properties), for each chemical species, only one phase is thermodynamically stable (i.e. have the lowest Gibbs free energy per volume), except on certain boundaries, such as the coexistence of ice and water right at the freezing point. In particular, since each crystal morph is a phase of matter, this implies that under normal circumstances, there exists only a single crystal morph at thermodynamic equilibrium. However, some phases may be kinetically stable, even if not energetically so. Disappearing polymorphs occur when there are two morphs of a substance, and one morph has lower Gibbs free energy, but is kinetically slower to form. Thus, when the crystal is first formed, the kinetically faster morph occurs first. Eventually, by accident or catalysis, the other morph occurs, which can then serve as seed crystal. More abstractly stated, disappearing polymorphs are morphs that are kinetically stable but not thermodynamically stable.
In pharmacology, bioavailability is a subcategory of absorption and is the fraction (%) of an administered drug that reaches the systemic circulation. By definition, when a medication is administered intravenously, its bioavailability is 100%. However, when a medication is administered via routes other than intravenous, its bioavailability is lower due to intestinal epithelium absorption and first-pass metabolism. Thereby, mathematically, bioavailability equals the ratio of comparing the area under the plasma drug concentration curve versus time (AUC) for the extravascular formulation to the AUC for the intravascular formulation. AUC is used because AUC is proportional to the dose that has entered the systemic circulation. Bioavailability of a drug is an average value; to take population variability into account, deviation range is shown as ±. To ensure that the drug taker who has poor absorption is dosed appropriately, the bottom value of the deviation range is employed to represent real bioavailability and to calculate the drug dose needed for the drug taker to achieve systemic concentrations similar to the intravenous formulation. To dose without knowing the drug taker's absorption rate, the bottom value of the deviation range is used in order to ensure the intended efficacy, unless the drug is associated with a narrow therapeutic window. For dietary supplements, herbs and other nutrients in which the route of administration is nearly always oral, bioavailability generally designates simply the quantity or fraction of the ingested dose that is absorbed.
While there are multiple proposed explanations for how SARS-CoV-2 was introduced into and evolved adaptations suited to human populations, there is significant evidence and agreement that the most likely original viral reservoir for SARS-CoV-2 is horseshoe bats. The closest known viral relatives of SARS-CoV-2 are BANAL-52 and RaTG13, sampled from horseshoe bat droppings in Feuang, Laos, and Yunnan province in China respectively. The evolutionary distance between SARS-CoV-2 and RaTG13 is estimated to be about 50 years (between 38 and 72 years). Bats are a significant reservoir species for a diverse range of coronaviruses, and humans have been found with antibodies for them suggesting that direct infection by bats is common. The zoonotic transmission of SARS-CoV-2 virus to humans took place in the context of exacerbating factors that could make such spillovers more likely. Human contact with bats has increased as human population centers encroach on bat habitats. Several social and environmental factors including climate change, natural ecosystem destruction and wildlife trade have also increased the likelihood for the emergences of zoonosis. One study made with the support of the European Union found climate change increased the likelihood of the pandemic by influencing distribution of bat species. The earliest human cases of SARS-CoV-2 were identified in Wuhan, but the index case remains unknown.
Sources: en.wikipedia.org
It is a tripeptide rather than a full protein. Proteins generally contain many amino acids joined by alpha-peptide bonds, while glutathione has three residues and an unusual gamma-glutamyl linkage. That structure affects how enzymes recognize and break it down.
GSH is the reduced form with a free thiol group. GSSG is the oxidized disulfide dimer formed when two GSH molecules react. The GSH-to-GSSG ratio is used in research as one indicator of cellular redox conditions.
Yes, it is present in many animal and plant tissues, including meats, some vegetables, and fruits. Heat, storage, and processing can reduce its content, so measured amounts vary widely.
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.