This is a working overview of thiol, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-04-01. Anything still debated is marked as such rather than presented as settled.
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.
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.
In living systems, glutathione occurs in millimolar concentrations in many cell types, while extracellular levels are generally much lower. The liver holds a substantial share of the body's total pool, and the molecule participates in reduction, detoxification, and amino acid transport. It also serves as a cofactor for enzymes such as glutathione peroxidase and glutathione S-transferase. Because the cysteine residue supplies a reactive thiol, glutathione can donate electrons and become oxidized. Cells regenerate reduced glutathione through glutathione reductase using NADPH.
Commercial glutathione is produced by microbial fermentation or chemical synthesis, then purified. Reduced and oxidized grades are offered separately, with purity specifications often exceeding 98 percent. The compound appears in foods such as fresh fruits, vegetables, and meats, although cooking and processing can lower amounts. Oral, topical, and inhaled forms are discussed in research and consumer contexts, but absorption and tissue delivery remain active areas of study. Regulatory status varies by country and intended use.
| 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. |
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.
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.
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.
In September 2019, Taco Bell revamped its menu for the fall season. In July 2020, Taco Bell announced the Grilled Cheese Burrito. The burrito is a recurring menu item that occasionally reappears for a limited time.
=== Megamolecules === Most recently, Mrksich's group has focused on developing a technique for assembling large molecular structures with perfectly defined structures and orientations, known as Megamolecules. This is primarily done through use of fusion proteins and irreversible inhibitor linkers that assemble stable intermediates. Structure-function relationships, including synthesis of cyclic and antibody-mimic structures have been investigated for potential therapeutic application.
== Susceptibility to infection == Pandemics such as COVID-19 show that people dramatically differ in their susceptibility to infection. This may be because of general health, age, or their immune status, e.g. when they have been infected previously. However, it also has become clear that there are genetic factors which determine susceptibility to infection. For instance, up to 40% of SARS-CoV-2 infections may be asymptomatic, suggesting that many people are naturally protected from disease. Large genetic studies have defined risk factors for severe SARS-CoV-2 infections, and genome sequences from 659 patients with severe COVID-19 revealed genetic variants that appear to be associated with life-threatening disease. One gene identified in these studies is type I interferon (IFN). Autoantibodies against type I IFNs were found in up to 13.7% of patients with life-threatening COVID-19, indicating that a complex interaction between genetics and the immune system is important for natural resistance to Covid. Similarly, mutations in the ERAP2 gene, encoding endoplasmic reticulum aminopeptidase 2, seem to increase the susceptibility to the plague, the disease caused by an infection with the bacteria Yersinia pestis. People who inherited two copies of a complete variant of the gene were twice as likely to have survived the plague as those who inherited two copies of a truncated variant. Susceptibility also determined the epidemiology of infection, given that different populations have different genetic and environmental conditions that affect infections.
Auxotrophy (Ancient Greek: αὐξάνω "to increase"; τροφή "nourishment") is the inability of an organism to synthesize a particular organic compound required for its growth (as defined by IUPAC). An auxotroph is an organism that displays this characteristic; auxotrophic is the corresponding adjective. Auxotrophy is the opposite of prototrophy, which is characterized by the ability to synthesize all the compounds needed for growth. Prototrophic cells are self-sufficient producers of all required metabolites (e.g. amino acids, lipids, cofactors), while auxotrophs require to be on medium with the metabolite that they cannot produce. For example, a methionine auxotrophic cell could only grow on a medium that contained methionine; otherwise, it would starve. In this example, this is because it is unable to produce its own methionine. However, a methionine prototrophic cell would be able to function and replicate on a medium with or without methionine. Replica plating is a technique that transfers colonies from one plate to another in the same spot as the last plate so the different media plates can be compared side by side. It is used to compare the growth of the same colonies on different plates of media to determine which environments the bacterial colony can or cannot grow in (this gives insight to possible auxotrophic characteristics). The method of replica plating implemented by Joshua Lederberg and Esther Lederberg included auxotrophs that were temperature-sensitive; that is, their ability to synthesize was temperature-dependent.
Sources: en.wikipedia.org
Many hormones and their structural and functional analogs are used as medication. The most commonly prescribed hormones are estrogens and progestogens (as methods of hormonal contraception and as HRT), thyroxine (as levothyroxine, for hypothyroidism) and steroids (for autoimmune diseases and several respiratory disorders). Insulin is used by many diabetics. Local preparations for use in otolaryngology often contain pharmacologic equivalents of adrenaline, while steroid and vitamin D creams are used extensively in dermatological practice. A "pharmacologic dose" or "supraphysiological dose" of a hormone is a medical usage referring to an amount of a hormone far greater than naturally occurs in a healthy body. The effects of pharmacologic doses of hormones may be different from responses to naturally occurring amounts and may be therapeutically useful, though not without potentially adverse side effects. An example is the ability of pharmacologic doses of glucocorticoids to suppress inflammation.
Viable yellow (Avy/a) and lethal yellow (Ay/a) heterozygotes have shortened life spans and increased risks for developing early onset obesity, type II diabetes mellitus and various tumors. The increased risk of developing obesity is due to the dysregulation of appetite, as agouti agonizes the agouti-related protein (AGRP), responsible for the stimulation of appetite via hypothalamic NPY/AGRP orexigenic neurons. Agouti also promotes obesity by antagonizing melanocyte-stimulating hormone (MSH) at the melanocortin receptor (MC4R), as MC4R is responsible for regulating food intake by inhibiting appetite signals. The increase in appetite is coupled to alterations in nutrient metabolism due to the paracrine actions of agouti on adipose tissue, increasing levels of hepatic lipogenesis, decreasing levels of lipolysis and increasing adipocyte hypertrophy. This increases body mass and leads to difficulties with weight loss as metabolic pathways become dysregulated. Hyperinsulinemia is caused by mutations to agouti, as the agouti protein functions in a calcium dependent manner to increase insulin secretion in pancreatic beta cells, increasing risks of insulin resistance. Increased tumor formation is due to the increased mitotic rates of agouti, which are localized to epithelial and mesenchymal tissues.
The tropical crown-of-thorns starfish (Acanthaster planci) is a voracious predator of coral throughout the Indo-Pacific region, and the Northern Pacific seastar is on a list of the Worst Invasive Alien Species. The fossil record for starfish is ancient, dating back to the Ordovician period around 450 million years ago, but it is rather sparse, as starfish tend to disintegrate after death. Only the ossicles and spines of the animal are likely to be preserved, making remains hard to locate. With their appealing symmetrical shape, starfish have played a part in literature and legend. They are sometimes collected as curios, used in design or as logos, and in some cultures they are eaten.
Sources: en.wikipedia.org
==== Victoria College fine arts ==== On 1 January 1992 further expansion of the college took place when the fine arts programs of the former Faculty of Art and Design, Victoria College (formerly Prahran College of Advanced Education), were incorporated into the School of Art.
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to form images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from computed tomography (CT) and positron emission tomography (PET) scans. MRI is a medical application of nuclear magnetic resonance (NMR) , which can also be used for imaging in other NMR applications, such as NMR spectroscopy. MRI is widely used in hospitals and clinics for medical diagnosis, staging and follow-up of disease. In the early 1970s, it was demonstrated by R. Damadian, C.F. Hazlewood and D.C. Chang that measurement of NMR relaxation times can be used to detect cancer. Soon after that, P.C. Lauterbur proposed to use a magnetic field gradient to generate the NMR image in a 2-D plane. Compared to CT, MRI provides better contrast in images of soft tissues, e.g. in the brain or abdomen. However, it may be perceived as less comfortable by patients, due to the usually longer and louder measurements with the subject in a long, confining tube, although "open" MRI designs mostly relieve this. Additionally, implants and other non-removable metal in the body can pose a risk and may exclude some patients from undergoing an MRI examination safely. MRI was originally called NMRI (nuclear magnetic resonance imaging), but "nuclear" was dropped to avoid negative associations.
Following the country's independence as Zimbabwe, Towsey became chargé d'affaires at the new embassy. The High Commission in London, known as Rhodesia House, continued to function until it was closed in 1969 following the decision by white Rhodesians in a referendum to make the country a republic, along with the "British Residual Mission" in Salisbury. Prior to its closure, the mission flew the newly adopted Flag of Rhodesia, considered illegal by the Foreign Office, prompting calls by Labour MP Willie Hamilton for its removal. In Australia, the federal government sought to close the Rhodesia Information Centre in Sydney, but it remained open, operating under the jurisdiction of the state of New South Wales. In 1973, the Labor government of Gough Whitlam cut post and telephone links to the centre, but this was ruled illegal by the High Court. An office was also established in Paris, but this was closed down by the French government in 1977. Similarly, the United States recalled its consul-general from Salisbury, and reduced consular staff, but did not move to close its consulate until the declaration of a republic in 1970. South Africa, however, retained its "Accredited Diplomatic Representative" after UDI, which allowed it to continue to recognise British sovereignty as well as to deal with the de facto authority of the government of Ian Smith. The South African Diplomatic Mission in Salisbury became the only such mission remaining in the country after 1975, when Portugal downgraded its mission to consul level, having recalled its consul-general in Salisbury in May 1970.
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.
It is a tripeptide rather than a full protein. Proteins generally contain many amino acids joined by alpha-peptide bonds, while glutathione has three residues and an unusual gamma-glutamyl linkage. That structure affects how enzymes recognize and break it down.