thiol group comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-03-16. Numbers and descriptions here follow the published literature rather than marketing material.
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 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.
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.
| 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 small tripeptide built from glutamate, cysteine, and glycine. The peptide bond between glutamate and cysteine uses the gamma-carboxyl group, a linkage that resists ordinary peptidases. Cells make it in two ATP-dependent steps: gamma-glutamylcysteine synthetase joins glutamate and cysteine, then glutathione synthetase adds glycine. The pathway is feedback-inhibited by glutathione itself, so intracellular levels tend to stay within a narrow range. Because cysteine is often limiting, sulfur amino acid supply influences how much glutathione a cell can produce.
In its reduced form, glutathione carries a sulfhydryl group that can donate electrons. This property lets it act as a major cellular antioxidant and redox buffer. Glutathione peroxidase uses it to reduce hydrogen peroxide and lipid peroxides, while glutathione reductase regenerates the reduced form using NADPH. The ratio of reduced glutathione to glutathione disulfide is widely used as an indicator of oxidative stress, though the ratio changes with compartment, cell type, and sample handling. Oxidized glutathione can also form mixed disulfides with proteins, affecting their activity.
Laboratory measurement of glutathione typically starts with rapid acid extraction to prevent oxidation and enzymatic degradation. Common methods include enzymatic recycling assays, high-performance liquid chromatography, and liquid chromatography coupled with mass spectrometry. The recycling assay uses glutathione reductase and a thiol-reactive colorimetric or fluorescent reagent, measuring total glutathione after converting disulfide forms. Chromatographic methods can separate reduced and oxidized forms, which helps when the redox ratio is the target. Choice of method affects sensitivity, specificity, and the amount of sample needed.
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.
====== Rosiglitazone ====== A combination of metformin and rosiglitazone was released in 2002, and sold as Avandamet by GlaxoSmithKline, or as a generic medication. Formulations are 500/1, 500/2, 500/4, 1000/2, and 1000 mg/4 mg of metformin/rosiglitazone. In 2009, it was the most popular metformin combination. In 2005, the stock of Avandamet was removed from the market, after inspections showed the factory where it was produced was violating good manufacturing practices. The medication pair continued to be prescribed separately, and Avandamet was again available by the end of that year. A generic formulation of metformin/rosiglitazone from Teva received tentative approval from the FDA and reached the market in early 2012. However, following a meta-analysis in 2007, that linked the medication's use to an increased risk of heart attack, concerns were raised over the safety of medicines containing rosiglitazone. In September 2010, the European Medicines Agency recommended that the medication be suspended from the European market because the benefits of rosiglitazone no longer outweighed the risks. It was withdrawn from the market in the UK and India in 2010, and in New Zealand and South Africa in 2011. From November 2011 until November 2013 the FDA did not allow rosiglitazone or metformin/rosiglitazone to be sold without a prescription; moreover, makers were required to notify patients of the risks associated with its use, and the drug had to be purchased by mail order through specified pharmacies.
==== Blood pressure ==== In the short term, nicotine causes a transient increase in blood pressure. Long term, epidemiological studies generally show increased blood pressure and hypertension among nicotine users.
==== Other optical imaging ==== For in vivo fluorescence-based optical imaging, dyes that emit near infrared (NIR) wavelengths >700 nm are most effective, such as indocyanine green, but encounter limitations with reduced circulation time and nonspecific interactions with other biological factors that affect the fluorescence. pH-sensitive nanogels with functionalized surface receptors to target cancer cells were loaded with a fluorescent dye that was only released upon endocytosis. These nanogels successfully generated a fluorescent signal from within the cancer cells and many other groups have developed similar technologies.
Sources: en.wikipedia.org
== History == Following World War II, Sonic founder Troy N. Smith Sr., returned to his hometown of Seminole, Oklahoma, where he became employed as a milkman. He then decided to work delivering bread, because bread is lighter than milk. Soon afterwards, Smith purchased the Cottage Cafe, a little diner in Shawnee, Oklahoma. Before long, he sold it and opened a fast-food service, Troy's Pan Full of Chicken, on the edge of town. In 1953, Smith joined with a business partner to purchase a five-acre parcel of land that had a log house and a walk-up root beer stand named the Top Hat. The two continued operating the root beer stand and converted the log house into a steak restaurant. After realizing that the stand was averaging $700 a week in the sale of root beer, hamburgers, and hot dogs, Smith decided to focus on the more-profitable root beer stand. He bought out his business partner. Initially, Top Hat customers parked their automobiles anywhere on the gravel parking lot and walked up to place orders. In Louisiana, Smith saw a drive-in that used speakers for ordering. He suspected that he could increase his sales by controlling the parking and having the customers order from speakers at their cars, with carhops delivering the food to the cars. Smith borrowed several automobiles from a friend who owned a used-car lot to establish a layout for controlled parking. He also had some so-called "jukebox boys" wire an intercom system in the parking lot. Sales immediately tripled. Charles Woodrow Pappe, an entrepreneur, was impressed by the Shawnee drive-in.
As early as 1996, dextromethorphan hydrobromide powder could be purchased in bulk from online retailers, allowing users to avoid consuming dextromethorphan in syrup preparations. FDA panels considered moving dextromethorphan to prescription status due to its potential for abuse, but voted against the recommendation in September 2010, citing lack of evidence that making it prescription-only would curb abuse. Some states have restricted the sale of dextromethorphan to adults or put other restrictions on its purchase in place, similar to those for pseudoephedrine. As of 1 January 2012, dextromethorphan is prohibited for sale to minors in the State of California and in the State of Oregon as of 1 January 2018, except with a doctor's prescription. Several other states have also begun regulating sales of dextromethorphan to minors. In Indonesia, the National Agency of Drug and Food Control (BPOM-RI) prohibited single-component dextromethorphan drug sales with or without prescription. Indonesia is the only country that makes single-component dextromethorphan illegal over the counter and by prescription and violators may be prosecuted by law. National Anti-Narcotics Agency (BNN RI) has threatened to revoke pharmacies' and drug stores' licenses if they still stock dextromethorphan, and will notify the police for criminal prosecution. As a result of this regulation, 130 medications have been withdrawn from the market, but those containing multicomponent dextromethorphan can still be sold over the counter.
== External links == "Parathyroid Hormone Receptors: PTH1". IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology. Archived from the original on 2011-05-16. Retrieved 2008-12-09. Receptor,+Parathyroid+Hormone,+Type+1 at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
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.
Preanalytical factors such as sample type, time to processing, and stabilization method can change GSH and GSSG amounts. Analytical method and calibration also contribute to variation. Comparing absolute values across studies requires caution.