If you have been reading about thiol group and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-07-17. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical formula | C10H17N3O6S | For reduced glutathione; the oxidized dimer has two sulfur atoms. |
| Molar mass | 307.32 g/mol | Calculated for the reduced form. |
| Appearance | White to off-white crystalline powder | Typical for solid reagent; solutions are usually colorless. |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar organic solvents. |
| Typical storage | -20 °C, desiccated, protected from light | Limits oxidation, moisture uptake, and degradation. |
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. Its cysteine residue carries a thiol group, which allows the molecule to participate in reduction and oxidation reactions. The compound exists in most living cells, where the reduced form, often abbreviated GSH, is usually more abundant than the oxidized disulfide form, GSSG. Intracellular concentrations are commonly in the millimolar range, while extracellular concentrations are much lower. This uneven distribution supports its role as a major cellular redox buffer.
Cells synthesize glutathione through two ATP-dependent enzymatic steps. The first step combines glutamate and cysteine to form gamma-glutamylcysteine, catalyzed by glutamate-cysteine ligase. The second step adds glycine, producing the complete tripeptide, catalyzed by glutathione synthetase. Glutathione itself can inhibit the first enzyme, providing negative feedback when levels are high. Because cysteine is often limiting, its availability influences how quickly the pathway proceeds. These reactions occur in the cytosol, and the resulting glutathione can be distributed to other compartments.
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.
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.
=== Natural production === Natural vanillin is extracted from the seed pods of Vanilla planifolia, a vining orchid native to Mexico, but now grown in tropical areas around the globe. Madagascar is presently the largest producer of natural vanillin.
==== Secret burial ==== In rare cases, a known person may be buried without identification, perhaps to avoid desecration of the corpse, grave robbing, or vandalism of the burial site. This may be particularly the case with infamous or notorious figures. In other cases, it may be to prevent the grave from becoming a tourist attraction or a destination of pilgrimage. Survivors may cause the deceased to be buried in a secret location or other unpublished place, or in a grave with a false name (or no name at all) on the marker. Following Walt Disney's cremation, his ashes were buried in a secret location in Forest Lawn Memorial Park Cemetery, California. Some burial sites at Forest Lawn, such as those of Humphrey Bogart, Mary Pickford and Michael Jackson, are secluded in private gated gardens or mausoleums with no public access. A number of tombs are also kept from the public eye. Forest Lawn's Court of Honor indicates that some of its crypts have plots which are reserved for individuals who may be "voted in" as "Immortals"; no amount of money can purchase a place. Photographs taken at Forest Lawn are not permitted to be published, and their information office usually refuses to reveal exactly where the remains of famous people are buried.
Intensive insulin therapy or flexible insulin therapy is a therapeutic regimen for diabetes mellitus treatment. This newer approach contrasts with conventional insulin therapy. Rather than minimize the number of insulin injections per day (a technique which demands a rigid schedule for food and activities), the intensive approach favors flexible meal times with variable carbohydrate as well as flexible physical activities. The trade-off is the increase from 2 or 3 injections per day to 4 or more injections per day, which was considered "intensive" relative to the older approach. In North America in 2004, many endocrinologists prefer the term "flexible insulin therapy" (FIT) to "intensive therapy" and use it to refer to any method of replacing insulin that attempts to mimic the pattern of small continuous basal insulin secretion of a working pancreas combined with larger insulin secretions at mealtimes. The semantic distinction reflects changing treatment.
Sources: en.wikipedia.org
Pyrroloquinoline quinone (PQQ), also called methoxatin, is a redox cofactor and antioxidant. Quinoprotein glucose dehydrogenase is used as a glucose sensor in bacteria. PQQ stimulates growth in bacteria.
Philosopher Eric Voegelin stated that Marxism–Leninism is inherently oppressive, writing that the "Marxian vision dictated the Stalinist outcome not because the communist utopia was inevitable but because it was impossible." Criticism like this has itself been criticised for philosophical determinism, i.e. that the negative events in the movement's history were predetermined by their convictions, with historian Robert Vincent Daniels stating that Marxism was used to "justify Stalinism, but it was no longer allowed to serve either as a policy directive or an explanation of reality" during Stalin's rule. In contrast, E. Van Ree wrote that Stalin considered himself to be in "general agreement" with the classical works of Marxism until his death. Graeme Gill stated that Stalinism was "not a natural flow-on of earlier developments; [it was a] sharp break resulting from conscious decisions by leading political actors." Gill added that "difficulties with the use of the term reflect problems with the concept of Stalinism itself. The major difficulty is a lack of agreement about what should constitute Stalinism." Historians such as Michael Geyer and Sheila Fitzpatrick criticised the focus upon the upper levels of society and the use of Cold War concepts, such as totalitarianism, which have obscured the reality of Marxist–Leninist systems, such as that of the Soviet Union. Mervyn Matthews criticized Marxism–Leninism for failing to solve poverty, noting that a large number of people in the Soviet Union were still in poverty despite its planned economy.
GeneReviews/NCBI/NIH/UW entry on Early-Onset Familial Alzheimer Disease Amyloid+Protein+Precursor at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Entrez Gene: APP amyloid beta (A4) precursor protein (peptidase nexin-II, Alzheimer disease) Human APP genome location and APP gene details page in the UCSC Genome Browser.
Sources: en.wikipedia.org
==== 1990s ==== In June 1992, at the time of its initial public offering, Starbucks (ticker symbol: SBUX) had 140 outlets, with revenue of US$73.5 million, up from US$1.3 million in 1987. The company's market value was US$271 million by this time. The 12% portion of the company that was sold raised around US$25 million for the company, which enabled it to double its number of stores over the next two years. In 1994, Starbucks acquired The Coffee Connection, gaining the rights to use, make, market, and sell the "Frappuccino" beverage. The beverage was introduced under the Starbucks name in 1995. In 1999, Starbucks experimented by opening eateries in the San Francisco Bay Area, under the Circadia restaurant brand. At the same time, Starbucks converted its Seattle Circadia restaurant into a Café Starbucks. The same year, Starbucks acquired Pasqua Coffee—a San Francisco-based retail coffee chain that had almost 60 locations in San Francisco, Los Angeles, and New York City.
== Medical career == Farthing began his medical career in New Zealand where he practiced as a dermatologist. After five years, he moved abroad and worked for a year in Riyadh, Saudi Arabia. He then moved to England and joined St. Stephen's Hospital, London in Chelsea. Between 1985 and 1987, the numbers of AIDS patients treated at St Stephen's rose from a dozen to over 1000. From 1985 to 1988, he was involved in clinical trials for the antiretroviral drugs Thymosin, AZT and foscarnet. In 1987, he helped found the Kobler Center at St Stephen's Hospital which specialised in the treatment and research of HIV/AIDS. It was one of the first wards in the United Kingdom to specialise in the area. He was chair of the all-party parliamentary committee on AIDS during the late 1980s, and was instrumental in guiding the governments reaction to the AIDS crisis. In 1988, he was awarded a Churchill fellowship which allowed him to move to the United States of America where he studied AIDS at the Bellevue Hospital in New York. He later became the director of the hospital's AIDS treatment program. In 1994, he moved to Los Angeles where he became the principal investigator of the AIDS Healthcare Foundation, and in 2001, he was promoted to medical director. In 2007, he left the United States for Hong Kong where he joined Merck Sharp & Dohme. At the time of his death, he was director of medical affairs for infectious diseases in the Asia-Pacific.
If the argument holds, then Form 2 could be marketed as generics in 1995 at the expiration of the 1978 patent. Since an additional seven years of exclusive marketing is highly profitable, Glaxo fought back. In order to win the first Glaxo, Inc. v. Novopharm, Ltd case, Glaxo argued successfully that Form 1 could be produced according to the 1978 patent procedure in a carefully quarantined environment, and that Novopharm had been producing Form 2 due to disappearing polymorphs. The organic chemist Jack Baldwin, acting as a witness to Glaxo, had two of his postdoctoral researchers, for three times, produce Form 1 according to the 1978 patent procedure. Consequently, the court ruled that the 1985 patent is valid and covers Form 2. Subsequent to losing the case, Novopharm attempted to bring Form 1 to market, so Glaxo sued them again in the second Glaxo, Inc. v. Novopharm, Ltd case. Glaxo argued that Novopharm could not market generics containing even trace amounts of Form 2. In particular, that means any generic Zantac containing an infrared spectrogram peak at 1045 cm−1 infringes their 1985 patent. However, during the prosecution of the first case, Glaxo had already accepted that the 1985 patent covered only products containing chemicals with a specific, 29-peak infrared (IR) spectrum. This was intended to avoid double patenting—Glaxo had to emphasize the unique aspects of Form 2 to distinguish it from the invention described in the 1978 patent.
Sources: en.wikipedia.org
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.
It is synthesized in the body from amino acids, so it is not classified as an essential dietary nutrient for most people. Dietary and supplemental forms are studied for their effects on tissue levels and health markers. Evidence varies by population and outcome.
The phrase highlights its high intracellular concentration and its role in several antioxidant and detoxification reactions. It is not the only antioxidant, and the term can oversimplify its functions. Scientific descriptions usually specify the pathway or enzyme involved.
Common methods include enzymatic recycling assays, liquid chromatography, and mass spectrometry. Many protocols separate reduced glutathione from its oxidized disulfide form before detection.