If you have been reading about Redox buffer 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.
Updated 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Measuring glutathione requires attention to sample preparation because the molecule oxidizes readily. Blood, tissue, and cell samples are often treated with acid to precipitate proteins and stabilize the thiol. Without such steps, GSH can convert to GSSG or form mixed disulfides during storage. Analytical methods include spectrophotometric assays, high-performance liquid chromatography, and mass spectrometry. Each approach has different sensitivity, specificity, and susceptibility to interference from related compounds in complex matrices.
| 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 |
Glutathione supports detoxification by conjugating reactive electrophiles through glutathione S-transferases. The resulting conjugates are processed and exported, often after further metabolism. It also stores cysteine, transports amino acids across membranes through the gamma-glutamyl cycle, and assists in the maturation of iron-sulfur clusters and some prostaglandins. In plants, animals, and many microbes, the molecule appears in similar roles, but concentrations vary enormously between tissues. Liver, kidney, and red blood cells tend to contain high amounts, while blood plasma contains much less.
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.
Glutathione is synthesized in two ATP-dependent steps. First, gamma-glutamylcysteine synthetase links glutamate and cysteine; second, glutathione synthetase adds glycine to form the complete tripeptide. The pathway is feedback-inhibited by GSH itself, which helps maintain steady intracellular levels. Tissues vary widely in glutathione content, with the liver typically containing the highest concentrations, followed by the kidneys, lungs, and erythrocytes. Because cysteine is often limiting, its availability influences synthesis rates, and regulation of this pathway varies by cell type.
Glutathione serves as a cofactor for several enzymes, including glutathione peroxidase and glutathione S-transferase. These enzymes help reduce hydrogen peroxide and lipid peroxides, and they conjugate reactive electrophiles for excretion. The molecule also acts as a reservoir for cysteine, an amino acid that is prone to oxidation. In addition, glutathione participates in the metabolism of nitric oxide, leukotrienes, and prostaglandins. Its roles extend to cell signaling, apoptosis, and the regulation of protein function through S-glutathionylation.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. The peptide bond between glutamate and cysteine uses the gamma-carboxyl group of glutamate rather than the alpha-carboxyl group. This unusual linkage protects the molecule from many common peptidases. The cysteine side chain carries a thiol group that can undergo reversible oxidation. Because of this thiol, glutathione participates in redox reactions and helps maintain the reducing environment inside most cells in living systems.
In cells, glutathione exists mainly in a reduced form called GSH. When two GSH molecules react, they form oxidized glutathione, or GSSG, which contains a disulfide bond. The ratio of GSH to GSSG is often used as an indicator of oxidative stress. Enzymes such as glutathione peroxidase and glutathione reductase help cycle the molecule between these two states. This cycling supports antioxidant defense, detoxification of reactive molecules, and regulation of certain signaling pathways.
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.
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.
=== Physical === Physical deterioration of waterlogged wood can happen immediately through the evaporation of the water. If this happens rapidly, the cells in the wood can shrink and collapse. This damage might be inevitable depending on accessibility to treatment. Additionally waterlogged wood should never be handled extensively or put on exhibit for long periods of time. Most waterlogged wood is such that decayed wood cells in the material fill with water. Depending on the wood type and how long the wood has been in water, removal of the water from the cells too rapidly (in the form of natural drying or other) could apply major stress to the cell walls and cause them to collapse. Improperly dried waterlogged irreversibly shrinks, warps, cracks and there is risk of loss to the original surface.
=== Genetics === Type 1 diabetes is partially caused by genetics, and family members of type 1 diabetics have a higher risk of developing the disease themselves. In the general population, the risk of developing type 1 diabetes is around 1 in 250. For someone whose parent has type 1 diabetes, the risk rises to 1–9%. If a sibling has type 1 diabetes, the risk is 6–7%. If someone's identical twin has type 1 diabetes, they have a 30–70% risk of developing it themselves. About half of the disease's heritability is due to variations in three HLA class II genes involved in antigen presentation: HLA-DRB1, HLA-DQA1, and HLA-DQB1. The variation patterns associated with increased risk of type 1 diabetes are called HLA-DR3 and HLA-DR4-HLA-DQ8, and are common in people of European descent. A pattern associated with reduced risk of type 1 diabetes is called HLA-DR15-HLA-DQ6. Large genome-wide association studies have identified dozens of other genes associated with type 1 diabetes risk, mostly genes involved in the immune system.
=== Skin === The rheumatoid nodule, which is sometimes in the skin, is the most common non-joint feature and occurs in 30% of people who have RA. It is a type of inflammatory reaction known as a "necrotizing granuloma". The initial pathologic process in nodule formation is unknown but may be essentially the same as the synovitis, since similar structural features occur in both. The nodule has a central area of fibrinoid necrosis that may be fissured and which corresponds to the fibrin-rich necrotic material found in and around an affected synovial space. Surrounding the necrosis is a layer of palisading macrophages and fibroblasts, corresponding to the intimal layer in synovium and a cuff of connective tissue containing clusters of lymphocytes and plasma cells, corresponding to the subintimal zone in synovitis. The typical rheumatoid nodule may be a few millimetres to a few centimetres in diameter and is usually found over bony prominences, such as the elbow, the heel, the knuckles, or other areas that sustain repeated mechanical stress. Nodules are associated with a positive RF (rheumatoid factor) titer, ACPA, and severe erosive arthritis. Rarely, these can occur in internal organs or at diverse sites on the body. Several forms of vasculitis occur in RA, but are mostly seen with long-standing and untreated disease. The most common presentation is due to involvement of small- and medium-sized vessels. Rheumatoid vasculitis can thus commonly present with skin ulceration and vasculitic nerve infarction known as mononeuritis multiplex.
=== EC 1.6.5 With a quinone or similar compound as acceptor === EC 1.6.5.1: deleted EC 1.6.5.2: NAD(P)H dehydrogenase (quinone) EC 1.6.5.3: now EC 7.1.1.2 NADH:ubiquinone reductase (H+-translocating) EC 1.6.5.4: monodehydroascorbate reductase (NADH) EC 1.6.5.5: NADPH:quinone reductase EC 1.6.5.6: p-benzoquinone reductase (NADPH) EC 1.6.5.7: 2-hydroxy-1,4-benzoquinone reductase EC 1.6.5.8: Now EC 7.2.1.1, NADH:ubiquinone reductase (Na+-transporting) EC 1.6.5.9: NADH:ubiquinone reductase (non-electrogenic) EC 1.6.5.10: NADPH dehydrogenase (quinone) EC 1.6.5.11: Identical to EC 1.6.5.9, NADH:quinone reductase (non-electrogenic) EC 1.6.5.12: demethylphylloquinone reductase
Sources: en.wikipedia.org
Depolarization opens both the sodium and potassium channels in the membrane, allowing the ions to flow into and out of the axon, respectively. If the depolarization is small (say, increasing Vm from −70 mV to −60 mV), the outward potassium current overwhelms the inward sodium current and the membrane repolarizes back to its normal resting potential around −70 mV. However, if the depolarization is large enough, the inward sodium current increases more than the outward potassium current and a runaway condition (positive feedback) results: the more inward current there is, the more Vm increases, which in turn further increases the inward current. A sufficiently strong depolarization (increase in Vm) causes the voltage-sensitive sodium channels to open; the increasing permeability to sodium drives Vm closer to the sodium equilibrium voltage ENa≈ +55 mV. The increasing voltage in turn causes even more sodium channels to open, which pushes Vm still further towards ENa. This positive feedback continues until the sodium channels are fully open and Vm is close to ENa. The sharp rise in Vm and sodium permeability correspond to the rising phase of the action potential. The critical threshold voltage for this runaway condition is usually around −45 mV, but it depends on the recent activity of the axon. A cell that has just fired an action potential cannot fire another one immediately, since the Na+ channels have not recovered from the inactivated state. The period during which no new action potential can be fired is called the absolute refractory period.
A few days later, on December 7, Webb engaged two hobbyists, Edgar Van Horn and Ernest Howatt, to photograph the carcass for posterity. At least two photographs were taken, one of the lateral view and one of the anterior view, showing the apparent arm stumps. The latter also included a man, likely DeWitt Webb himself, for scale. As the images were over-exposed, they were never published. These photographs were for a long time considered lost, and only drawings based on them, made by Alpheus Hyatt Verrill and published in the American Naturalist of April 1897, were known. However, one of the original images, showing the lateral view, was obtained by Gary Mangiacopra in 1994. It is clear that one of Verrill's drawings was based on this photograph. A simplified drawing of this image also appeared in the Hartford Daily Running of February 18, 1897. Around the same time, a certain Mr. Wilson wrote a memorandum to Webb, communicating the results of his observations made after having dug around the corpse. It read:
NFEPP (N-(3-fluoro-1-phenethylpiperidin-4-yl)-N-phenylpropionamide) is an analgesic opioid chemical, similar in structure to fentanyl, designed in 2016 by Spahn et al. from Free University of Berlin to avoid the standard negative side effects of opiates, including opioid overdose, by only targeting inflamed tissue.
== Oldest biochemistry department in the world == The current department is directly descended from the original Biochemistry Department, the world's first and oldest, which was created in 1902 at the University of Liverpool through a philanthropic donation. The early years of Liverpool biochemistry (1902–1971) are discussed in depth in official archives and the 100th anniversary was officially celebrated in 2002. The original Biochemistry building in the university quadrangle remains the site of occasional 'pilgrimages' from other long-established Biochemistry Departments such as those affiliated with the University of Toronto and the Indian Institute of Science in Bengaluru, whose Department of Biochemistry was created in 1921 and remains an official partner, as part of the University of Liverpool campus in Bengaluru, India announced in 2025
The common krait (Bungarus caeruleus) is often considered to be the most dangerous snake species in India. Its venom consists mostly of powerful neurotoxins which induce muscle paralysis. Clinically, its venom contains presynaptic and postsynaptic neurotoxins. Due to the fact that krait venom contains many presynaptic neurotoxins, patients bitten will often not respond to antivenom because once paralysis has developed it is not reversible. This species causes an estimated 10,000 fatalities per year in India alone. There is a 70–80% mortality rate in cases where there is no possible or poor and ineffective treatment (e.g., no use of mechanical ventilation, low quantities of antivenom, poor management of possible infection). Average venom yield per bite is 10 mg (Brown, 1973), 8 to 20 mg (dry weight) (U.S. Dept. Navy, 1968), and 8 to 12 mg (dry weight) (Minton, 1974). The lethal adult human dose is 2.5 mg. In mice, the LD50 values of its venom are 0.365 mg/kg SC, 0.169 mg/kg IV and 0.089 mg/kg IP.
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.
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.