A practical reference on thiol group: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-02-07 and is reviewed periodically as new material appears.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. Its glutamate-cysteine linkage uses the gamma-carboxyl group of glutamate, a feature that resists standard peptidases. The cysteine residue provides a thiol group, which gives the molecule its reducing character. In cells, glutathione is often the most abundant small-molecule thiol, with concentrations varying widely by tissue and compartment. It exists mainly in a reduced form called GSH, while oxidation produces a disulfide-linked dimer called GSSG.
Biosynthesis proceeds in two ATP-dependent steps. First, glutamate-cysteine ligase joins glutamate and cysteine. Second, glutathione synthetase adds glycine to the intermediate. The pathway is regulated by cysteine availability, enzyme expression, and feedback inhibition by glutathione itself. Liver tissue has a particularly high capacity for synthesis and export. Because the molecule is made inside cells, circulating glutathione reflects a balance of release, uptake, and breakdown rather than simple dietary supply.
Functionally, glutathione supports redox balance by donating electrons and becoming oxidized. It also serves as a cofactor for enzymes such as glutathione peroxidases and glutathione S-transferases. These enzymes participate in peroxide reduction and in conjugation reactions that help process reactive molecules. Separate from antioxidant roles, glutathione can modify protein cysteines through S-glutathionylation, influencing enzyme activity and signaling. Research continues to examine how these chemical roles translate into whole-organism effects.
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.
| Property | Value | Notes |
|---|---|---|
| Common name | Glutathione (reduced form) | Often abbreviated GSH |
| Chemical class | Tripeptide | Contains glutamate, cysteine, and glycine |
| Molecular formula | C10H17N3O6S | Refers to the reduced form |
| Molar mass | 307.32 g/mol | Calculated for C10H17N3O6S |
| Appearance | White to off-white powder | Typical laboratory-grade solid |
Glutathione functions in redox balance, detoxification, and sulfur amino acid storage. It participates in reactions that help maintain ascorbate and protein thiol status. The molecule serves as a cofactor for several enzymes, including glutathione peroxidases and glutathione S-transferases. These enzymes reduce peroxides and conjugate electrophiles, respectively. Glutathione also contributes to the metabolism of xenobiotics and to the transport of cysteine between tissues. How interorgan transport and tissue-specific regulation shape whole-body pools remains an active area of study.
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.
Samples for glutathione analysis require careful handling because the compound oxidizes readily and can be consumed by enzymes after collection. Blood is often treated with acid or thiol-blocking agents soon after draw, and plasma should be separated quickly from red blood cells. Tissues are usually snap-frozen or extracted immediately. Aqueous solutions of glutathione are less stable than dry powder and degrade faster at neutral or alkaline pH, in light, or with dissolved oxygen. Repeated freeze-thaw cycles also reduce reliability.
Quality control for glutathione materials checks identity, assay, purity, water content, and disulfide content. Commercial products vary from research-grade powder to dietary supplements, and labels may not distinguish reduced from oxidized forms. In the United States, oral glutathione is commonly sold as a dietary supplement rather than an approved drug, while injectable forms fall under different rules and may require a prescription. Regulatory status differs by country. Analytical certificates, when available, help verify what a material contains, but independent testing remains important for interpretation.
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.
The Port of Hong Kong, located by the South China Sea, is a deepwater seaport dominated by trade in containerised manufactured products. A key factor in the economic development of Hong Kong, the natural shelter and deep waters of Victoria Harbour provide ideal conditions for berthing and the handling of all types of vessels. It is one of the busiest ports in the world, in the three categories of shipping movements, cargo handled, and passengers carried. This makes Hong Kong a Large-Port Metropolis. The Star Ferry operates two lines across Victoria Harbour for its 53,000 daily passengers. Ferries also serve outlying islands inaccessible by other means. Smaller kai-to boats serve the most remote coastal settlements. Ferry travel to Macau and mainland China is also available. Junks, once common in Hong Kong waters, are no longer widely available and are used privately and for tourism. The large size of the port gives Hong Kong the classification of Large-Port Metropolis.
== Folk medicine == Cannabis tea was used for centuries in folk medicine as it was thought to be a treatment for rheumatism, cystitis, and various urinary diseases. In an article in Nature, it is projected that cannabis has been used medicinally for nearly 12,000 years. The oldest confirmed reference to medicinal cannabis is ~2700 BC, in Ancient China. There is ~190AD evidence that a Chinese physician, Hua T'o, used an emulsion of tea and wine to anesthetize a patient for surgery. According to a short communication published in the Journal of Ethnopharmacology, based on the research of Zias et al. regarding cannabis use in ancient childbirth, cannabis is said to have been used to assist women during childbirth. The communication is regarding an anthropological find of a birthing mother, dated to the 4th century AD., "We assume that the ashes found in the tomb were cannabis, burned in a vessel and administered to the young girl as an inhalant to facilitate the birth process." Cannabis tea has been traditionally used by Jamaican women as a remedy for morning sickness associated with pregnancy. There is no evidence that cannabis is an abortive medicine."
=== Evaluation of a technique === The technique being evaluated uses voltammetric sensors combined in an electronic tongue (ET) to observe the antioxidant capacity in red wines. These electronic tongues (ETs) consist of multiple sensing units like voltammetric sensors, which will have unique responses to certain compounds. This approach is optimal to use since samples of high complexity can be analyzed with high cross-selectivity. Thus, the sensors can be sensitive to pH and antioxidants. As usual, the voltage in the cell was monitored using a working electrode and a reference electrode (silver/silver chloride electrode). Furthermore, a platinum counter electrode allows the current to continue to flow during the experiment. The Carbon Paste Electrodes sensor (CPE) and the Graphite-Epoxy Composite (GEC) electrode are tested in a saline solution before the scanning of the wine so that a reference signal can be obtained. The wines are then ready to be scanned, once with CPE and once with GEC. While cyclic voltammetry was successfully used to generate currents using the wine samples, the signals were complex and needed an additional extraction stage. It was found that the ET method could successfully analyze wine's antioxidant capacity as it agreed with traditional methods like TEAC, Folin-Ciocalteu, and I280 indexes. Additionally, the time was reduced, the sample did not have to be pretreated, and other reagents were unnecessary, all of which diminished the popularity of traditional methods.
Carbohydrates are compounds made up of types of sugar. Carbohydrates are classified according to their number of sugar units: monosaccharides (such as glucose and fructose), disaccharides (such as sucrose and lactose), oligosaccharides, and polysaccharides (such as starch, glycogen, and cellulose). Proteins are organic compounds that consist of amino acids joined by peptide bonds. Since the body cannot manufacture some of the amino acids (termed essential amino acids), the diet must supply them. Through digestion, proteins are broken down by proteases back into free amino acids. Fats consist of a glycerin molecule with three fatty acids attached. Fatty acid molecules contain a -COOH group attached to unbranched hydrocarbon chains connected by single bonds alone (saturated fatty acids) or by both double and single bonds (unsaturated fatty acids). Fats are needed for construction and maintenance of cell membranes, to maintain a stable body temperature, and to sustain the health of skin and hair. Because the body does not manufacture certain fatty acids (termed essential fatty acids), they must be obtained through one's diet.
Sources: en.wikipedia.org
By September 2017, the club had reached out-of-court compensation deals with all players, covering potential and actual loss of earnings and mental anguish; the sizes of the deals were confidential, but the largest payouts were understood to have gone to Jobe Watson, who was stripped of the Brownlow Medal, and Stewart Crameri, who missed the Western Bulldogs' 2016 premiership. Despite the top-up players, the weakened Essendon team was mostly uncompetitive during 2016, finishing last on the ladder with just three wins to win the wooden spoon for the first time since 1933. The club's win–loss record of 3–19 was, at the time, the second-worst in club history, and included a club-record seventeen-game losing streak (since equalled between 2025–26). Financially, the club posted a $9.8 million uninsured operating loss for the season, with roughly half of the cost in legal fees and compensation payments to the guilty players, and with reduced receipts and the payments to top-up players also having a significant effect. Ten of the twelve suspended players re-signed with Essendon for 2017; the two who departed were Michael Hibberd, who was traded to Melbourne, and Tayte Pears, who retired. There was speculation that the players could have left the club en masse, with lawyers arguing that Essendon's role in the scandal could have been considered a breach of contract, allowing the players to get out of their playing contracts and bypass other AFL player movement restrictions to qualify as delisted free agents, but no players sought this option.
=== Radiological scope === Contrast agents with therapeutic properties have been under development for several years. One example is the design of contrast agents capable of releasing a chemotherapeutic agent locally at the target site, triggered by a stimulus provided by the operator. This localized approach aims to increase treatment efficacy and minimize side effects. For instance, ultrasound-based contrast media, such as microbubbles, can accumulate in hypervascularized tissues and release the active ingredient in response to ultrasound waves, thus targeting a specific area chosen by the sonographer. Another approach involves linking monoclonal antibodies (capable of targeting different molecular targets) to nanoparticles. This strategy enhances the drug's affinity and specificity towards the target and enables visualization of the treatment area, such as using superparamagnetic iron oxide particles detectable by magnetic resonance imaging. Additionally, these particles can be designed to release chemotherapy agents specifically at the site of binding, producing a local synergistic effect with antibody action. Integrating these methods with medical-nuclear techniques, which offer greater imaging sensitivity, may aid in target identification and treatment monitoring.
On 19 June 2024, she received an honorary doctorate from the University of Cambridge in recognition of her achievements in chemistry. In 2024, she was inducted into the National Academy of Inventors. She has been awarded 13 honorary doctorates including the Weizmann Institute of Science, Aarhus University Denmark, University of Kent, the University of York, and the University of Bristol. On 10 August 2025, Robinson appeared on BBC Radio 4's Desert Island Discs.
Food and Beverage Electronics and High-Tech Healthcare and Pharma Fast Moving Consumer Goods (FMCG) Retail E-commerce and Parcels Automotive Industrial and Manufacturing Fashion and Lifestyle Agricultural Cosmetics and Hygiene Chemicals
=== Separation Processes === King wrote the book Separation Processes in 1971. In the book, King presented that each of the separation processes (distillation, extraction, absorption, etc.) is a special case of a unified technology that can be described by a general set of quantitative principles. Before that, the standard separation operations were considered to be separate topics within the category of unit operations, with separate methodologies. The book was revised for a second edition in 1980. After the book went out of print, King secured the copyright back from McGraw-Hill and put it on eScholarship, where it is available open-access.
Sources: en.wikipedia.org
Glutathione is a sulfur-containing tripeptide made from glutamate, cysteine, and glycine. It is found in most cells and participates in redox balance and detoxification reactions.
No. It is a tripeptide assembled from three amino acids. The term amino acid applies to the individual building blocks, not to the assembled molecule.
It is present in many tissues, with especially high amounts in liver. Intracellular concentrations are generally much higher than those found in blood plasma.
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.