The short version of gamma-glutamyl cycle fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-08-26 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Typical analytical method | LC-MS/MS, HPLC, or enzymatic recycling | Choice depends on whether total, reduced, or oxidized glutathione is measured. |
| Sample stabilization | Acidification or thiol alkylation | Helps limit conversion of GSH to GSSG after collection. |
| Solution stability | Limited at room temperature | Oxidation and pH-dependent degradation can occur. |
| Storage of solid | -20 °C, desiccated, protected from light | Common for research reagents; follow supplier instructions. |
| Common interference | Other thiols and metal ions | Can affect separation or enzymatic detection. |
Glutathione reference materials are sensitive to oxygen, light, and elevated temperature. Solid material is typically stored desiccated at -20 °C or below, while solutions require tighter control because thiol oxidation proceeds faster in liquid form. Aqueous solutions are often prepared fresh, kept cold, and protected from air; some protocols add acid or chelating agents to slow metal-catalyzed oxidation. Repeated freeze-thaw cycles can accelerate degradation and should be avoided. Stability data vary by matrix, so laboratories usually verify performance with their own storage conditions.
Quality control for glutathione measurements includes calibration with authenticated standards, internal standards where available, blank correction, and spike recovery checks. Because glutathione can form during sample processing or degrade before analysis, pre-analytical handling is a major source of variability. Interlaboratory comparisons often show differences in reported values due to method-specific calibration and detection principles. Interpretive thresholds are context-dependent, and no single reference range applies across all tissues or matrices. Researchers generally report both reduced and oxidized forms, along with the method and sample handling details.
Interpreting glutathione measurements requires attention to pre-analytical variables. The GSSG concentration in a sample can rise artificially during storage or processing, making the GSH/GSSG ratio unreliable if not controlled. Reference ranges vary by specimen type, assay, and population, so comparisons across studies are difficult. Plasma glutathione is low and sensitive to hemolysis, while whole blood reflects primarily erythrocyte content. Many studies measure total glutathione rather than the reduced and oxidized forms separately, which limits conclusions about redox status.
Accurate measurement of glutathione begins with careful sample handling. Because GSH oxidizes rapidly to GSSG, samples must be processed quickly or frozen immediately. Acid precipitation with metaphosphoric acid or perchloric acid is common; it lowers pH, precipitates proteins, and helps preserve the reduced form. Chelating agents such as EDTA can limit metal-catalyzed oxidation. For whole blood, hemolysis releases glutathione from erythrocytes, so plasma and serum values differ substantially from whole blood values.
Several analytical methods can quantify glutathione, including high-performance liquid chromatography (HPLC) with UV or fluorescence detection for separating GSH and GSSG. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) offers higher specificity and sensitivity, often detecting nanomolar concentrations. The enzymatic recycling assay, often called the Tietze method, measures total glutathione by coupling reduction of GSSG to a colorimetric or fluorometric readout. Capillary electrophoresis and electrochemical detection are also used in specialized laboratories. Each method has distinct advantages and limitations regarding throughput, cost, and susceptibility to interference.
The Prausnitz–Küstner test (PK test, Prausnitz-Küstner reaction) is an immunologic test formerly used by physicians to determine if a patient has an allergic reaction to a specific antigen. The test has been replaced by the safer skin prick test. The PK test involves transferring serum from the test subject to another healthy person, essentially using the second person as a mixing vessel for antibodies and antigen. This is a pathway for transmission of blood-borne ailments like variant Creutzfeldt–Jakob disease, AIDS, and others, which is why the test is no longer recommended. Or in simple words, a test for the presence of immediate hypersensitivity in humans; test serum from an atopic individual is injected intradermally into a normal subject; the normal subject is challenged 24–48 hours later with the antigen suspected of causing the immediate hypersensitivity reaction in the atopic individual.
Diphtheria toxin is produced by virulent Corynebacterium diphtheriae that infect the mucosal membranes of the throat and nasal cavity causing a gray, thickened lining of the throat, sore throat, weakness, mild fever, swollen glands of the neck, and difficulty breathing. Diphtheria toxin is an ADP-ribosyltransferase that inhibits protein synthesis which causes the symptoms associated with the disease. Diphtheria used to be a leading cause of childhood death until the creation of a vaccine. The diphtheria vaccine contains a diphtheria toxoid, antigenically identical yet inactivated and non-toxic. When the toxoid is introduced to the body in a vaccine, an immune response is mounted without sequelae associated with the toxigenicity.
In 1955, a USAF surgeon who advised the US Surgeon General wrote an article on how to make cars safer for those riding in it. Aside from the usual safety features, such as seat belts and padded dashboards, bumper shocks were introduced. In 1956, Ford tried unsuccessfully to interest Americans in purchasing safer cars with their Lifeguard safety package. (Its attempt nevertheless earns Ford Motor Trend's "Car of the Year" award for 1956.) In 1958, the United Nations established the World Forum for Harmonization of Vehicle Regulations, an international standards body advancing auto safety. Many of the most life saving safety innovations, like seat belts and roll cage construction were brought to market under its auspices. That same year, Volvo engineer Nils Bohlin invented and patented the three-point lap and shoulder seat belt, which became standard equipment on all Volvo cars in 1959. Over the next several decades, three-point safety belts were gradually mandated in all vehicles by regulators throughout the industrialised world. In 1959, American Motors Corporation offered the first optional head rests for the front seat. Also in 1959, the Cadillac Cyclone concept by Harley Earl had "a radar-based crash-avoidance system" located on the nose cones of the vehicle that would make audible and visual signals to the driver if there were obstacles in the vehicle's path.
Sources: en.wikipedia.org
This is the largest division of the Society. It marked its 100th anniversary in 2008. The first Chair of the Division was Edward Curtis Franklin. The Organic Division played a part in establishing Organic Syntheses, Inc. and Organic Reactions, Inc. and it maintains close ties to both organizations. The Division's best known activities include organizing symposia (talks and poster sessions) at the biannual ACS National Meetings, for the purpose of recognizing promising Assistant Professors, talented young researchers, outstanding technical contributions from junior-level chemists, in the field of organic chemistry. The symposia also honor national award winners, including the Arthur C. Cope Award, Cope Scholar Award, James Flack Norris Award in Physical Organic Chemistry, Herbert C. Brown Award for Creative Research in Synthetic Methods. The Division helps to organize symposia at the international meeting called Pacifichem and it organizes the biennial National Organic Chemistry Symposium (NOS) which highlights recent advances in organic chemistry and hosts the Roger Adams Award address. The Division also organizes corporate sponsorships to provide fellowships for PhD students and undergraduates. It also organizes the Graduate Research Symposium and manages award and travel grant programs for undergraduates.
The peptide-mRNA:cDNA fusions can be selected over immobilized selection targets for several rounds (Figure 3). There might be a relatively high background for the first few rounds of selection, and this can be minimized by increasing selection stringency, such as adjusting salt concentration, amount of detergent, and/or temperature during the target/fusion binding period. Following binding selection, those library members that stay bound to the immobilized target are PCR amplified. The PCR amplification step will enrich the population from the mRNA-display library that has higher affinity for the immobilized target. Error-prone PCR can also be done in between each round of selection to further increase the diversity of the mRNA-display library and reduce background in selection. A less time-consuming protocol for mRNA display was recently published.
The National Institute for Health and Clinical Excellence (NICE), UK released updated diabetes recommendations on 30 May 2008, which recommend that self-monitoring of plasma glucose levels for people with newly diagnosed type 2 diabetes must be integrated into a structured self-management education process. The recommendations have been updated in August 2015 for children and young adults with type 1 diabetes. The American Diabetes Association (ADA), which produces guidelines for diabetes care and clinical practice recommendations, recently updated its "Standards of Medical Care" in January 2019 to acknowledge that routine self-monitoring of blood glucose in people who are not using insulin is of limited additional clinical benefit. A randomized controlled trial evaluated once-daily self-monitoring that included tailored patient messaging and did not show that this strategy led to significant changes in A1C after a year. Media related to Blood glucose monitoring at Wikimedia Commons
Activated carbon, in 50% w/w combination with celite, is used as stationary phase in low-pressure chromatographic separation of carbohydrates (mono-, di-, tri-saccharides) using ethanol solutions (5–50%) as mobile phase in analytical or preparative protocols. Activated carbon is useful for extracting the direct oral anticoagulants (DOACs) such as dabigatran, apixaban, rivaroxaban and edoxaban from blood plasma samples. For this purpose it has been made into "minitablets", each containing 5 mg activated carbon for treating 1ml samples of DOAC. Since this activated carbon has no effect on blood clotting factors, heparin or most other anticoagulants this allows a plasma sample to be analyzed for abnormalities otherwise affected by the DOACs. Carbon adsorption has numerous applications in removing pollutants from air or water streams both in the field and in industrial processes such as:
Sources: en.wikipedia.org
The reaction catalyzed by 1-aminocyclopropane-1-carboxylic acid synthase (ACS) is the committed and rate-limiting step in the biosynthesis of ethylene [20], a gaseous plant hormone that is responsible for the initiation of fruit ripening, shoot and root growth and differentiation, leaf and fruit abscission, flower opening, and flower and leaf senescence. (source) It is a pyridoxal phosphate (PLP) dependent gamma-elimination (?). In the gamma elimination, PLP acts as a sink twice (absorbing electrons from two deprotonations). Proposed steps of the reaction mechanism: Formation of the ACS-PLP Schiff Base Imine Exchange Formation of the Quinonoid Intermediate Tyrosine and PLP stabilized 3C-Ring formation Formation of the ACS-PLP Schiff Base The aldehyde of coenzyme PLP reacts to form an imine (Schiff base) linkage with the catalytic domain lysine (278) residue of ACS. Imine exchange An imine exchange occurs, and the amine nitrogen of the substrate, S-Adenosyl methionine, replaces Lys (278) in the imine linkage. (Stabilized by H bonding).
The ABCB subfamily is composed of four full transporters and two half transporters. This is the only human subfamily to have both half and full types of transporters. ABCB1 was discovered as a protein overexpressed in certain drug resistant tumor cells. It is expressed primarily in the blood–brain barrier and liver and is thought to be involved in protecting cells from toxins. Cells that overexpress this protein exhibit multi-drug resistance.
Cholecystokinin tetrapeptide (CCK-4, tetragastrin, Trp-Met-Asp-Phe-NH2) is a peptide fragment derived from the larger peptide hormone cholecystokinin. Unlike cholecystokin which has a variety of roles in the gastrointestinal system as well as central nervous system effects, CCK-4 acts primarily in the brain as an anxiogenic, although it does retain some GI effects, but not as much as CCK-8 or the full length polypeptide CCK-58. CCK-4 reliably causes severe anxiety symptoms when administered to humans in a dose of as little as 50 μg, and is commonly used in scientific research to induce panic attacks for the purpose of testing new anxiolytic drugs. Since it is a peptide, CCK-4 must be administered by injection, and is rapidly broken down once inside the body so has only a short duration of action, although numerous synthetic analogues with modified properties are known. Pentagastrin
The tertiary structure and topology of TMEM125 was predicted and visualized through Phyre2. TMEM125 has 1 predicted phosphorylation site (CK2 Phos), 5 predicted N-myristoylation sites (N-myr), 2 predicted palmitoylation sites (Pal), and 1 predicted amidation site (Amid). It also contains the domain of unknown function 66 (DUF66). TMEM125 is predicted to be subcellularly localized in the plasma membrane. It is secondarily predicted to be localized in the endoplasmic reticulum. There were no scientifically-verified protein interactions identified for TMEM125. String Protein Interaction predicted 10 functional protein partners for TMEM125, but all were determined through textmining. TMEM125 is conserved in species as distantly related to humans as cartilaginous fish, that’s most recent common ancestor to humans existed 465 million years ago. TMEM125 is highly conserved in primates, mammals, birds, reptiles, bony fish, and cartilaginous fish, but is not observed in invertebrates. TMEM125 does not have any paralogs.
Alfred Stracher (1931-2013) was an American biochemist and the founder and editor-in-chief of Drug Delivery. During his lifetime, he was Distinguished Professor of Biochemistry at SUNY Downstate Medical Center. Alfred Stracher was born in Albany, New York in 1931. He graduated from Rensselaer Polytechnic Institute in 1952 with a Bachelor of Science in Chemistry. He received his PhD in Chemistry from Columbia University in 1956.
Sources: en.wikipedia.org
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.
These assays typically measure total glutathione after oxidizing or reducing steps convert GSSG to GSH. A colorimetric or fluorometric signal is proportional to the recycling reaction. They generally do not report GSH and GSSG separately unless additional steps are used.
Solutions are often prepared fresh and kept cold, with protection from light and oxygen exposure. Chelating agents may reduce metal-catalyzed oxidation. Storage recommendations vary by buffer, pH, and concentration, so protocol-specific guidance should be followed.
Glutathione is built from three amino acids: glutamate, cysteine, and glycine. The linkage involves the gamma-carboxyl group of glutamate rather than the alpha-carboxyl group, which is unusual for peptides. This structure protects the bond from some common peptidases.