The short version of Tietze assay fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-07-22. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common analytical method | LC-MS/MS or HPLC | Separation of GSH and GSSG |
| Limit of detection | Nanomolar range | Method dependent |
| Typical sample storage | -80 °C | For biological matrices |
| Common reducing agent | TCEP or DTT | Prevents oxidation during processing |
| Common synonym | Gamma-glutamylcysteinylglycine | Systematic name |
=== Surgery === The decision to observe or treat a nevus may depend on a number of factors, including cosmetic concerns, irritative symptoms (e.g., pruritus), ulceration, infection, and concern for potential malignancy.
Alternatives to the above closed-channel continuous-flow systems include novel open structures, where discrete, independently controllable droplets are manipulated on a substrate using electrowetting. Following the analogy of digital microelectronics, this approach is referred to as digital microfluidics. Le Pesant et al. pioneered the use of electrocapillary forces to move droplets on a digital track. The "fluid transistor" pioneered by Cytonix also played a role. The technology was subsequently commercialised by Duke University. By using discrete unit-volume droplets, a microfluidic function can be reduced to a set of repeated basic operations, i.e., moving one unit of fluid over one unit of distance. This "digitisation" method facilitates the use of a hierarchical and cell-based approach for microfluidic biochip design. Therefore, digital microfluidics offers a flexible and scalable system architecture as well as high fault-tolerance capability. Moreover, because each droplet can be controlled independently, these systems also have dynamic reconfigurability, whereby groups of unit cells in a microfluidic array can be reconfigured to change their functionality during the concurrent execution of a set of bioassays. Although droplets are manipulated in confined microfluidic channels, since the control on droplets is not independent, it should not be confused as "digital microfluidics". One common actuation method for digital microfluidics is electrowetting-on-dielectric (EWOD).
Political observers have called Xi the most powerful Chinese leader since Chairman Mao Zedong, especially since the ending of presidential two-term limits in 2018. Xi has departed from the CCP's previous collective leadership practices. Observers have said that Xi has seriously diluted the influence of the once-dominant Tuanpai, also called the Youth League Faction, which were CCP officials who rose through the Communist Youth League (CYLC). Xi has had a cult of personality constructed around himself since entering office with books, cartoons, pop songs and dance routines honouring his rule. Xi's cult of personality has been especially pronounced in Xinjiang. In 2016, the sixth plenary session of the 18th Central Committee officially announced Xi as the leadership core, making him the fourth leader to have been given this designation after Mao Zedong, Deng Xiaoping and Jiang Zemin; Hu Jintao was never given this designation.
== Lifetime == According to Vladimir Uglev, who headed a group that worked on the development of the Novichok agents, at least one liquid form of Novichok is very stable with a slow evaporation rate and can remain potent for possibly up to 50 years. Insufficient research has been conducted to fully understand its persistence in various situations in the environment.
Sources: en.wikipedia.org
=== Cellulose nanocrystals === Cellulose nanocrystals (CNC) are rod like particles formed by the acid hydrolysis of native cellulose fibers, most commonly using sulfuric or hydrochloric acid. Disordered sections of native cellulose are hydrolysed and after careful timing, the remaining crystalline sections can be retrieved from the acid solution by centrifugation and dialysis against water. Their final dimensions depend on the cellulose source, its history, the hydrolysis conditions and the purification procedures. CNCs are commercialised by various companies that use different sources and processes, leading to a range of available products.
Similarly, some theories of well-being are species-relative, proposing that the essential features of well-being vary across distinct species, for example, that the well-being of humans differs from the well-being of non-human animals.
=== Patent === Toward the end of January 1922, tensions mounted between the four "co-discoverers" of insulin and Collip briefly threatened to separately patent his purification process. John G. FitzGerald, director of the non-commercial public health institution Connaught Laboratories, therefore stepped in as peacemaker. The resulting agreement of 25 January 1922 established two key conditions: 1) that the collaborators would sign a contract agreeing not to take out a patent with a commercial pharmaceutical firm during an initial working period with Connaught; and 2) that no changes in research policy would be allowed unless first discussed among FitzGerald and the four collaborators. It helped contain disagreement and tied the research to Connaught's public mandate.
The origins of the present international illegal heroin trade can be traced back to laws passed in many countries in the early 1900s that closely regulated the production and sale of opium and its derivatives including heroin. At first, heroin flowed from countries where it was still legal into countries where it was no longer legal. By the mid-1920s, heroin production had been made illegal in many parts of the world. An illegal trade developed at that time between heroin labs in China (mostly in Shanghai and Tianjin) and other nations. The weakness of the government in China and conditions of civil war enabled heroin production to take root there. Chinese triad gangs eventually came to play a major role in the illicit heroin trade. The French Connection route started in the 1930s. Heroin trafficking was virtually eliminated in the US during World War II because of temporary trade disruptions caused by the war. Japan's war with China had cut the normal distribution routes for heroin and the war had generally disrupted the movement of opium. After World War II, the Mafia took advantage of the weakness of the postwar Italian government and set up heroin labs in Sicily which was located along the historic route opium took westward into Europe and the United States. Large-scale international heroin production effectively ended in China with the victory of the communists in the civil war in the late 1940s. The elimination of Chinese production happened at the same time that Sicily's role in the trade developed.
=== Paul trap === A Paul trap (also known as a quadrupole ion trap) uses static direct current (DC) and radio frequency (RF) oscillating electric fields to trap ions. Paul traps are commonly used as components of mass spectrometers. Wolfgang Paul invented the Paul trap, hence its name. For this work he shared the 1989 Nobel Prize in Physics.
Sources: en.wikipedia.org
=== Nuclear testing and Use of Outer-Space treaties === The Partial Nuclear Test Ban Treaty was signed on August 5, 1963, by the United States, the Soviet Union, and over 100 other nations. This treaty banned nuclear weapons tests in the atmosphere, outer space, and underwater, restricting such tests to underground environments. The treaty followed heightened concerns over the militarization of space, amplified by the United States' Starfish Prime test in 1962, which involved the detonation of a nuclear device in the upper atmosphere. To further delineate the peaceful use of outer space, the United Nations facilitated the drafting of the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, commonly known as the Outer Space Treaty. Signed on January 27, 1967, by the United States, the Soviet Union, and the United Kingdom, it entered into force on October 10, 1967. The treaty established space as a domain to be used exclusively for peaceful purposes, prohibiting the placement of nuclear weapons or any other weapons of mass destruction in orbit or on celestial bodies.
=== February === February 13, 2009: Netherlands The Dutch Statistics agency confirms the Netherlands are in recession since April 2008; with updated figures showing minor economic reductions in the 2nd and 3rd quarters of 2008, and a 0.9% reduction in the 4th quarter
Charles Dickens, a keen observer, described possible bilateral optic neuritis with reduced contrast vision and Uhthoff's phenomenon in the main female character of Bleak House (1852–1853), Esther Summerson.
Secondary-ion mass spectrometry (SIMS) is a technique used to analyze the composition of solid surfaces and thin films by sputtering the surface of the specimen with a focused primary ion beam and collecting and analyzing ejected secondary ions. The mass/charge ratios of these secondary ions are measured with a mass spectrometer to determine the elemental, isotopic, or molecular composition of the surface to a depth of 1 to 2 nm. Due to the large variation in ionization probabilities among elements sputtered from different materials, comparison against well-calibrated standards is necessary to achieve accurate quantitative results. SIMS is the most sensitive elemental surface analysis technique, with elemental detection limits ranging from parts per million to parts per billion.
Sources: en.wikipedia.org
Glutathione oxidizes quickly when cells are disrupted or when samples sit at room temperature. Rapid processing or immediate freezing minimizes the conversion of GSH to GSSG. This step helps ensure that the measured ratio reflects the original biological state.
The Tietze assay is an enzymatic recycling method that measures total glutathione. It uses glutathione reductase to reduce GSSG back to GSH, which then reacts with a chromogen or fluorophore. The reaction cycles repeatedly, amplifying the signal for detection.
Yes, but the choice of blood fraction matters. Plasma or serum contains low glutathione levels and is easily affected by hemolysis. Whole blood mainly reflects the high glutathione content of erythrocytes, so results from different fractions are not directly comparable.
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.