If you have been reading about liquid chromatography 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 2026-06-26. Where a claim depends on a specific study, the study is described rather than over-claimed.
Within cells, glutathione serves as a cofactor for glutathione peroxidases and glutathione S-transferases. These enzymes reduce hydrogen peroxide and organic peroxides or conjugate electrophilic compounds to the thiol group. The resulting conjugates can be exported and processed through mercapturic acid pathways. Glutathione also contributes to protein thiol homeostasis and to recycling of other antioxidants such as ascorbate. Its precise roles vary by tissue, and many regulatory effects observed in laboratory systems remain difficult to quantify in whole organisms.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. It occurs in nearly all living cells, with highest concentrations in liver, kidney, and red blood cells, and exists in reduced (GSH) and oxidized disulfide (GSSG) forms. The cysteine thiol group enables reversible oxidation and reduction reactions. This property makes glutathione a central participant in cellular redox balance. The balance between these forms is often used as an indicator of oxidative stress.
Glutathione synthesis proceeds in two ATP-dependent steps catalyzed by glutamate-cysteine ligase and glutathione synthetase. The first step joins glutamate and cysteine to form gamma-glutamylcysteine and is generally rate-limiting. The second step adds glycine to complete the tripeptide. Cysteine availability, feedback inhibition by glutathione, and oxidative conditions influence flux through this pathway. The pathway is conserved across many organisms, and degradation by gamma-glutamyl transpeptidase and related peptidases recycles amino acids for new synthesis.
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.
Quantification of glutathione in biological or food samples commonly uses liquid chromatography coupled to ultraviolet, fluorescence, electrochemical, or mass spectrometric detection. Because the thiol group oxidizes readily, samples are often acidified or derivatized immediately after collection to stabilize reduced glutathione. Enzymatic recycling assays and colorimetric kits offer higher throughput but generally lower specificity than chromatographic methods. Mass spectrometry can distinguish glutathione from related thiols and allow simultaneous measurement of oxidized forms. Reported concentrations depend strongly on sample type, extraction procedure, and analytical platform.
| Property | Value | Notes |
|---|---|---|
| Common name | Glutathione | Reduced form is abbreviated GSH |
| Chemical class | Tripeptide | Composed of glutamate, cysteine, and glycine |
| Molar mass | 307.32 g/mol | For reduced glutathione |
| CAS Registry Number | 70-18-8 | For reduced L-glutathione |
| Appearance | White crystalline powder | Typical solid reference material |
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.
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.
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.
After Harrison Stanford Martland (1883-1954), chief medical examiner in Essex County, detected the radioactive noble gas radon (a decay product of radium) in the breath of the Radium Girls, he turned to Charles Norris (1867-1935) and Alexander Oscar Gettler (1883-1968). In 1928, Gettler was able to detect a high concentration of radium in the bones of Amelia Maggia, one of the young women, even five years after her death. In 1931, a method was developed for determining radium dosage using a film dosimeter. A standard preparation is irradiated through a hardwood cube onto an X-ray film, which is then blackened. For a long time, the cube minute was an important unit of radium dosage. It was calibrated by ionometric measurements. The radiologists Hermann Georg Holthusen (1886-1971) and Anna Hamann (1894-1969) found a calibration value of 0.045 r/min in 1932/1935. The calibration film receives the y-ray dose of 0.045 r per minute through the wooden cube from the preparation of 13.33 mg. In 1933, the physicist Robley D. Evans (1907-1995) made the first measurements of radon and radium in the excretions of female workers. On this basis, the National Bureau of Standards, the predecessor to the National Institute of Standards and Technology (NIST), set the limit for radium at 0.1 microcuries (about 3.7 kilobecquerels) in 1941. A Radium Action Plan 2015-2019 aims to solve the problem of radiological contamination in Switzerland, mainly in the Jura Mountains, due to the use of radium luminous paint in the watch industry until the 1960s.
==== Protease-specific Arrays ==== A protease specific protein array based on immobilized antibodies designed to capture specific proteases from biological samples offers a step up in analysis of protein levels beyond transcript expression. Capture antibodies spotted to nitrocellulose membranes can bind proteases in complex mixtures which have been pre-incubated and bound by detection antibodies allowing for parallel analysis of relative protease levels. These arrays offer parallelization of protein levels over traditional western blot. Unfortunately, these assays fail to provide insight on enzymatic function for proteases and suffer similar drawbacks to western blots regarding reliable quantification.
Martin Fleischmann of the University of Southampton and Stanley Pons of the University of Utah hypothesized that the high compression ratio and mobility of deuterium that could be achieved within palladium metal using electrolysis might result in nuclear fusion. To investigate, they conducted electrolysis experiments using a palladium cathode and heavy water within a calorimeter, an insulated vessel designed to measure process heat. Current was applied continuously for many weeks, with the heavy water being renewed at intervals. Some deuterium was thought to be accumulating within the cathode, but most was allowed to bubble out of the cell, joining oxygen produced at the anode. For most of the time, the power input to the cell was equal to the calculated power leaving the cell within measurement accuracy, and the cell temperature was stable at around 30 °C. But then, at some point (in some of the experiments), the temperature rose suddenly to about 50 °C without changes in the input power. These high temperature phases would last for two days or more and would repeat several times in any given experiment once they had occurred. The calculated power leaving the cell was significantly higher than the input power during these high temperature phases. Eventually the high temperature phases would no longer occur within a particular cell. In 1988, Fleischmann and Pons applied to the United States Department of Energy for funding towards a larger series of experiments. Up to this point they had been funding their experiments using a small device built with $100,000 out-of-pocket.
== Etymology == The word water comes from Old English wæter, from Proto-Germanic *watar (source also of Old Saxon watar, Old Frisian wetir, Dutch water, Old High German wazzar, German Wasser, vatn, Gothic 𐍅𐌰𐍄𐍉 (wato)), from Proto-Indo-European *wod-or, suffixed form of root *wed- ('water'; 'wet'). Also cognate, through the Indo-European root, with Greek ύδωρ (ýdor; from Ancient Greek ὕδωρ (hýdōr), whence English 'hydro-'), Russian вода́ (vodá), Irish uisce, and Albanian ujë.
Several trials have attempted dietary interventions with the hope of reducing the autoimmunity that leads to type 1 diabetes. Trials that withheld cow's milk or gave infants formula free of bovine insulin decreased the development of β-cell-targeted antibodies, but did not prevent the development of type 1 diabetes. Similarly, trials that gave high-risk individuals injected insulin, oral insulin, or nicotinamide did not prevent diabetes development. Other strategies under investigation for the prevention of type 1 diabetes include gene therapy, stem cell therapy, and modulation of the gut microbiome. Gene therapy approaches are still in early stages. They aim to alter genetic factors that contribute to beta-cell destruction by editing immune responses. Stem cell therapies are also being researched, with the hope that they can either regenerate insulin-producing beta cells or protect them from immune attack. Trials using stem cells to restore beta cell function or regulate immune responses are ongoing. Modifying the gut microbiota through the use of probiotics, prebiotics, or specific diets has also gained attention. Some evidence suggests that the gut microbiome plays a role in immune regulation, and researchers are investigating whether altering the microbiome could reduce the risk of autoimmunity and, subsequently, type 1 diabetes. Tolerogenic therapies, which seek to induce immune tolerance to beta-cell antigens, are another area of interest.
Sources: en.wikipedia.org
Workers exposed to high air levels of copper (resulting in an estimated intake of 200 mg Cu/d) developed signs suggesting copper toxicity (e.g., elevated serum copper levels, hepatomegaly). However, other co-occurring exposures to pesticidal agents or in mining and smelting may contribute to these effects. Effects of copper inhalation are being thoroughly investigated by an industry-sponsored program on workplace air and worker safety. This multi-year research effort is expected to be finalized in 2011.
==== Deal brokered ==== The Gulf Co-operation Council applied no small amount of pressure on Saleh to negotiate an end to the uprising by stepping down. Weeks after returning from Saudi Arabia, Saleh finally agreed on 23 November to resign in exchange for immunity. As part of the deal, the opposition agreed to allow Hadi to stand unopposed for the presidency in 2012.
In both males and females, FSH stimulates the maturation of primordial germ cells. In males, FSH induces Sertoli cells to secrete androgen-binding proteins (ABPs), regulated by inhibin's negative feedback mechanism on the anterior pituitary. Specifically, activation of Sertoli cells by FSH sustains spermatogenesis and stimulates inhibin B secretion. In females, FSH initiates follicular growth, specifically affecting granulosa cells. With the concomitant rise in inhibin B, FSH levels then decline in the late follicular phase. This seems to be critical in selecting only the most advanced follicle to proceed to ovulation. At the end of the luteal phase, there is a slight rise in FSH that seems to be of importance to start the next ovulatory cycle. Control of FSH release from the pituitary gland is unknown. Low frequency gonadotropin-releasing hormone (GnRH) pulses increase FSH mRNA levels in the rat, but is not directly correlated with an increase in circulating FSH. GnRH has been shown to play an important role in the secretion of FSH, with hypothalamic–pituitary disconnection leading to a cessation of FSH. GnRH administration leads to a return of FSH secretion. FSH is subject to oestrogen feed-back from the gonads via the hypothalamic pituitary gonadal axis.
== Side effects == The most common adverse effects in studies were upper respiratory tract infection, headache, nausea, and diarrhea. The most common side effects in clinical trials were nasopharyngitis, nausea, headaches, herpes simplex (including oral herpes, ophthalmic herpes, herpes dermatitis and genital herpes), and increase in blood creatine phosphokinase. Abrocitinib can cause serious infections, malignancy, major cardiac events, thrombosis and other laboratory abnormalities including thrombocytopenia, lymphopenia, and lipid elevations. However, according to clinical data, Abrocitinib is well tolerated. The total adverse reactions were not statistically different between the placebo and the dose of 100 mg of abrocitinib. However, it was slightly higher for the dose of 200 mg of abrocitinib. Symptoms such as acne, headache, and nausea, appeared in the first two weeks of starting abrocitinib, and it was not necessary to interrupt the treatment. In general, the AE frequency of abrocitinib was the same or a little bit higher than in case of placebo or dupilumab.
Sources: en.wikipedia.org
This process is extremely painful and can traumatize the animal. Freeze branding gained popularity in the middle of the 20th century as a less painful way to permanently mark and identify animals. There has been debate as to whether freeze branding is truly less painful than hot branding, but scientific studies conducted to compare the relative pain of the two methods have concluded that freeze branding is indeed less distressing to the animal being marked. Freeze brands are made for a variety of purposes. For example, they are used to indicate that an animal belongs to a particular herd, all members of which are marked with the same brand. They are also used to indicate via a unique pattern that an individual animal is a particular person's or ranch's property. Freeze branding is also used to tag wild animals that will be recaptured for later research.
== Pathology == Abnormally elevated levels of glucagon may be caused by pancreatic tumors, such as glucagonoma, symptoms of which include necrolytic migratory erythema, reduced amino acids, and hyperglycemia. It may occur alone or in the context of multiple endocrine neoplasia type 1. Elevated glucagon is the main contributor to hyperglycemic ketoacidosis in undiagnosed or poorly treated type 1 diabetes. As the beta cells cease to function, insulin and pancreatic GABA are no longer present to suppress the freerunning output of glucagon. As a result, glucagon is released from the alpha cells at a maximum, causing a rapid breakdown of glycogen to glucose and fast ketogenesis. It was found that a subset of adults with type 1 diabetes took 8 hours longer on average (18 hours vs 10 hours) to approach ketoacidosis when given somatostatin (inhibits glucagon production) with no insulin. Inhibiting glucagon has been a popular idea of diabetes treatment, however, some have warned that doing so will give rise to brittle diabetes in patients with adequately stable blood glucose. The absence of alpha cells (and hence glucagon) is thought to be one of the main influences in the extreme volatility of blood glucose in the setting of a total pancreatectomy.
Water is released, and the second o-quinone product is formed together with the restoration of the initial Cu(II)-Cu(II) state to complete the catalytic cycle. This proposed catalytic cycle is supported by the experimental observation that stoichiometric amounts of o-quinone form after catechol addition to the enzyme, even when dioxygen is absent. Furthermore, both the oxidized Cu(II)-Cu(II) state and the reduced Cu(I)-Cu(I) state were the two states identified by the crystal structure of Ipomoea batatas. The monodentate binding of catechol to the copper center was supported by the crystal structure of catechol oxidase bound with the bound-substrate analogue inhibitor phenylthiourea, which also binds to the copper center in a monodentate fashion. However, one issue with this catalytic cycle is that the charge of the active site changes during the catalytic cycle from +1 to +3. This necessitates the presence of nearby bases that can store the protons; however, the X-ray crystal structure does not indicate the presence of any such bases as the histidine residues are coordinated with the copper centers. Other catalytic cycles elucidated with DFT calculations and crystal structures have been proposed which maintain the same charge in the active site throughout the cycle and thus do not require nearby bases. However, certain intermediates in the proposed cycle are not consistent with experimental findings such as that stoichiometric amounts of o-quinone can form after catechol addition in the absence of oxygen.
Sources: en.wikipedia.org
GSH is the reduced thiol form, while GSSG is the disulfide-linked oxidized dimer. The GSH:GSSG ratio is used as a redox indicator, though the ratio can vary with sample handling and cell type.
Glutathione is present in many foods, including meats, poultry, fish, some vegetables, and fruits. Cooking, storage, and digestion affect the amounts available for absorption.
Yes, both enzymatic steps in glutathione synthesis consume ATP. The first step, catalyzed by glutamate-cysteine ligase, is usually rate-limiting.
Acidification lowers pH and helps prevent oxidation of the thiol group during extraction and storage. It can also precipitate proteins and stabilize the reduced form before analysis.