If you have been reading about mass spectrometry 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 2026-05-10. Where a claim depends on a specific study, the study is described rather than over-claimed.
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, and it is the most abundant non-protein thiol in most living cells. The reduced form, GSH, carries a sulfhydryl group that can donate electrons, while the oxidized form, GSSG, forms when two GSH molecules link via a disulfide bond. The balance between these two forms helps define the cellular redox environment, and their ratio is often used as an indicator of oxidative stress. Because the sulfhydryl group is reactive, glutathione participates in many cellular processes, including detoxification and protein regulation.
Stability depends on pH, temperature, oxygen exposure, and trace metals. Aqueous solutions of reduced glutathione are susceptible to oxidation, especially when neutral or alkaline and exposed to air. Transition metal ions can catalyze thiol oxidation, so chelators and inert atmospheres are sometimes used in research settings. Standards are typically stored cold and desiccated, with limited freeze-thaw cycles. Questions remain about how closely in vitro stability data reflect the behavior of glutathione within intact cells and tissues.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical formula | C10H17N3O6S | Reduced form (GSH) |
| Molar mass | 307.32 g/mol | For GSH; GSSG is 612.63 g/mol |
| Appearance | White crystalline powder | Usually lyophilized |
| Solubility in water | Freely soluble (≥100 mg/mL) | pH dependent |
| Typical storage | -20 °C, desiccated | Protect from light and oxygen |
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.
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.
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.
Enzymatic recycling assays provide a complementary approach for total glutathione. In these methods, glutathione reductase reduces oxidized glutathione while a thiol-reactive reagent, such as 5,5'-dithiobis(2-nitrobenzoic acid), produces a colored product. The reaction cycles between reduced and oxidized forms, amplifying the signal. Spectrophotometric or fluorometric detection can then estimate concentration. Distinguishing reduced glutathione from glutathione disulfide often requires separate aliquots, masking agents, or chromatographic separation, and the choice affects reported values.
Storage conditions strongly influence glutathione stability. The solid reduced form is commonly kept desiccated at or below minus twenty degrees Celsius, protected from light and moisture. Aqueous solutions are less stable because the thiol group reacts with dissolved oxygen, and oxidation accelerates at neutral or alkaline pH. Acidic solutions and oxygen-free handling can slow degradation, but repeated freeze-thaw cycles should be avoided. Researchers often verify concentration before use, because apparent losses can arise from oxidation or water uptake.
Measuring glutathione in biological samples requires attention to oxidation and matrix effects. High-performance liquid chromatography with ultraviolet or fluorescence detection can separate reduced and oxidized forms after derivatization. Liquid chromatography with tandem mass spectrometry offers higher specificity and can quantify glutathione alongside related thiols. Because glutathione can oxidize during sample handling, many protocols use rapid acidification with metaphosphoric acid or sulfosalicylic acid. Internal standards help correct for losses during extraction and analysis.
Commercial glutathione is available in research-grade, food-grade, and supplement-grade forms, and purity specifications differ accordingly. Certificates of analysis commonly report identity by nuclear magnetic resonance or mass spectrometry, purity by HPLC, residual solvents, and heavy metals. Reference standards with assigned purity support calibration, while isotopically labeled glutathione can serve as an internal standard for mass spectrometry. For supplements, label claims may not be independently verified, and regulatory oversight varies by country. Verification often involves third-party testing for identity, potency, and contaminants.
Quantifying glutathione requires distinguishing GSH from GSSG and preventing oxidation during sample preparation. Common approaches include the enzymatic recycling assay, often called the Tietze method, which measures total glutathione after converting GSSG to GSH. HPLC with ultraviolet or fluorescence detection and LC-MS/MS can separate and quantify both forms, sometimes after derivatization of the thiol group. Blood, plasma, and tissue samples differ in matrix and baseline concentrations, so method validation must account for recovery, linearity, and interference. No single assay is universally standard.
=== Walter Bennett === Dr. Walter Bennett (voiced by Harry S. Robins) is a Black Mesa scientist. He is seen in Half-Life: Blue Shift. In Blue Shift, Dr. Bennett is seen fixing a battery in Dr. Rosenberg's office, along with Dr. Simmons. The three scientists soon get it fixed with the help of Barney Calhoun, and they start their teleportation out of Black Mesa. The four successfully make it out of the facility, making Dr. Bennett one of the few known survivors of the incident. They open the gates and start their journey to the outside world with an SUV. Dr. Bennett is briefly mentioned in Half-Life: Opposing Force. As Adrian Shephard traverses within Sector E of Black Mesa, he enters a testing laboratory where Xen specimens were being experimented on prior to the Resonance Cascade. He opens up a transmission intended for Dr. Bennett, revealing a hologram of a scientist talking about the results of an experiment conducted on a Barnacle, which was one of the Xen creatures being examined. Following the transmission, Shephard takes a nearby Barnacle specimen that was intended for Dr. Bennett to experiment on before the Resonance Cascade. Dr. Bennett's final fate is unknown.
In boosted fission weapons a mix of 2H and 3H is heated until there is thermonuclear fusion to produce helium and free neutrons. These fast neutrons then cause further fission, creating "boosting". In 1951, in Operation Greenhouse, a prototype named George, validated the proof of concept for such a weapon. However, the first true boosted fission bomb, Greenhouse Item, was successfully tested in 1952, giving a 45.5-kiloton yield, nearly double that of an unboosted bomb. The United States stopped producing tritium in nuclear reactors in 1988, but nuclear tests in the 1950s added large spikes of radionuclides to the air, especially carbon-14 and 3H. This complicated measurements for geologists using carbon dating. However, some oceanographers benefited from the 3H increase, using the signal in the water to trace physical mixing of water masses.
An overview of the history was published in 2012. In 1934, the Hungarian physician Paul György discovered a substance that was able to cure a skin disease in rats (dermatitis acrodynia). He named this substance vitamin B6, as numbering of the B vitamins was chronological, and pantothenic acid had been assigned vitamin B5 in 1931. In 1938, Richard Kuhn was awarded the Nobel Prize in Chemistry for his work on carotenoids and vitamins, specifically B2 and B6. Also in 1938, Samuel Lepkovsky isolated vitamin B6 from rice bran. A year later, Stanton A. Harris and Karl August Folkers determined the structure of pyridoxine and reported success in chemical synthesis, and then in 1942 Esmond Emerson Snell developed a microbiological growth assay that led to the characterization of pyridoxamine, the aminated product of pyridoxine, and pyridoxal, the formyl derivative of pyridoxine. Further studies showed that pyridoxal, pyridoxamine, and pyridoxine have largely equal activity in animals and owe their vitamin activity to the ability of the organism to convert them into the enzymatically active form pyridoxal-5-phosphate. Following a recommendation of IUPAC-IUB in 1973, vitamin B6 is the official name for all 2-methyl,3-hydroxy,5-hydroxymethylpyridine derivatives exhibiting the biological activity of pyridoxine. Because these related compounds have the same effect, the word "pyridoxine" should not be used as a synonym for vitamin B6.
. The Burnett equations include additional second-order derivatives of velocity, temperature, and density, representing more subtle effects of non-equilibrium gas dynamics. The Burnett equations can be expressed as:
Levothyroxine, also known as L-thyroxine, is a synthetic form of the thyroid hormone thyroxine (T4). It is used to treat thyroid hormone deficiency (hypothyroidism), including a severe form known as myxedema coma. It may also be used to treat and prevent certain types of thyroid tumors. It is not indicated for weight loss. Levothyroxine is taken orally (by mouth) or given by intravenous injection. Levothyroxine has a half-life of 7.5 days when taken daily, so about six weeks is required for it to reach a steady level in the blood. Side effects from excessive doses include weight loss, trouble tolerating heat, sweating, anxiety, trouble sleeping, tremor, and fast heart rate. Use is not recommended in people who have had a recent heart attack. Use during pregnancy has been found to be safe. Dosing should be based on regular measurements of thyroid-stimulating hormone (TSH) and T4 levels in the blood. Much of the effect of levothyroxine is following its conversion to triiodothyronine (T3). Levothyroxine was first made in 1927. It is on the World Health Organization's List of Essential Medicines. Levothyroxine is available as a generic medication. In 2024, it was the second most commonly prescribed medication in the United States, with more than 80 million prescriptions.
Sources: en.wikipedia.org
Distal stabilisation of muscles is often performed. This allows effective muscle contraction which reduces atrophy, allows functional use of the stump and maintains soft tissue coverage of the remnant bone. The preferred stabilisation technique is myodesis where the muscle is attached to the bone or its periosteum. In joint disarticulation amputations tenodesis may be used where the muscle tendon is attached to the bone. Muscles are attached under similar tension to normal physiological conditions. An experimental technique known as the "Ewing amputation" aims to improve post-amputation proprioception. Another technique with similar goals, which has been tested in a clinical trial, is Agonist-antagonist Myoneural Interface (AMI). In 1920, Dr. Janos Ertl Sr. of Hungary, developed the Ertl procedure in order to return a high number of amputees to the workforce. The Ertl technique, an osteomyoplastic procedure for transtibial amputation, can be used to create a highly functional residual limb. Creation of a tibiofibular bone bridge provides a stable, broad tibiofibular articulation that may be capable of some distal weight bearing. Several different modified techniques and fibular bridge fixation methods have been used; however, no current evidence exists regarding comparison of the different techniques.
In Australia, iced coffee may include syrup, cream, cocoa powder or coffee beans. The café style is something like an unblended milkshake, and may be made from espresso coffee or only coffee flavoring. Bushells has marketed a Coffee and Chicory Essence since the late 19th century, as has Bickfords since 1910. There are many brands of packaged iced coffee consisting of coffee, milk, and sweetener. In South Australia, Farmers Union Iced Coffee has outsold Coca-Cola and is one of the state's biggest brands. Pauls "Territory's Own" Iced Coffee is popular in the Northern Territory and Norco Real Iced Coffee is prominent in Northern New South Wales and South East Queensland. Other brands include Breaka, Big M, Brownes Chill, Moove, Masters, Dare, Max, Fleurieu, Rush, Oak and Ice Break.
=== Spin transport === Graphene is considered an ideal material for spintronics due to its minimal spin–orbit interaction, the near absence of nuclear magnetic moments in carbon, and weak hyperfine interaction. Electrical injection and detection of spin current have been demonstrated up to room temperature, with spin coherence length exceeding 1 micrometer observed at this temperature. Control of spin current polarity via electrical gating has been achieved at low temperatures.
Restoration In nasal reconstruction, the plastic surgeon's ultimate goal is recreating the shadows, the contours, the skin color, and the skin texture that define the patient's "normal nose", as perceived at conversational distance (c. 1.0 metre). Yet, such an aesthetic outcome suggests the application of a more complex surgical approach, which requires that the surgeon balance the patient's required rhinoplasty, with the patient's aesthetic ideal (body image). In the context of surgically reconstructing the patient's physiognomy, the "normal nose" is the three-dimensional (3-D) template for replacing the missing part(s) of a nose (aesthetic nasal subunit, aesthetic nasal segment), which the plastic surgeon re-creates using firm, malleable, modelling materials—such as bone, cartilage, and flaps of skin and of tissue. In repairing a partial nasal defect (wound), such as that of the alar lobule (the dome above the nostrils), the surgeon uses the undamaged, opposite (contralateral) side of the nose as the 3-D model to fabricate the anatomic template for recreating the deformed nasal subunit, by molding the malleable template material directly upon the normal, undamaged nasal anatomy. To effect a total nasal reconstruction, the template might derive from quotidian observations of the "normal nose" and from photographs of the patient before they sustained the nasal damage.
=== History === In January 2009, the U.S. Department of Defense announced the largest RFID award in history, a $429 million contract for DASH7 devices, to four prime contractors, namely Savi Technology, Northrop Grumman Information Technology, Unisys and Systems & Processes Engineering Corporation (SPEC). In March 2009, the DASH7 Alliance, a non-profit industry consortium to promote interoperability among DASH7-compliant devices, was announced, and as of July 2010 has more than 50 participants in 23 countries. It was meant to be similar to what the Wi-Fi Alliance does for IEEE 802.11, for wireless sensor networking. In April 2011, the DASH7 Alliance announced adoption of DASH7 Mode 2, based on the ISO 18000-7 standard that makes better use of modern silicon to achieve faster throughput, multi-hop, lower latency, better security, sensor support, and a built-in query protocol. In March 2012, the DASH7 Alliance announced that it was making the DASH7 Mode 2 specification available to non-members. In July 2013, the DASH7 Alliance announced the DASH7 Alliance Protocol Draft 0.2. In May 2015, the DASH7 Alliance publicly released v1.0 of the DASH7 Alliance Protocol. In January 2017, the DASH7 Alliance publicly released the v1.1 of the DASH7 Alliance Protocol. The version constitutes a major update of v1.0, in particular in the area of security and interoperability.
Sources: en.wikipedia.org
Secondary food processing is the everyday process of creating food from ingredients that are ready to use. Baking bread, regardless of whether it is made at home, in a small bakery, or in a large factory, is an example of secondary food processing. Fermenting fish and making wine, beer, and other alcoholic products are traditional forms of secondary food processing. Sausages are a common form of secondary processed meat, formed by comminution (grinding) of meat that has already undergone primary processing. Most of the secondary food processing methods known to humankind are commonly described as cooking methods.
Ro64-6198 is an opioid drug used in scientific research. It acts as a potent and selective agonist for the nociceptin receptor, also known as the ORL-1 (opiate receptor like-1) receptor, with over 100x selectivity over the other opioid receptors. It produces anxiolytic effects in animal studies equivalent to those of benzodiazepine drugs, but has no anticonvulsant effects and does not produce any overt effects on behaviour. However it does impair short-term memory, and counteracts stress-induced anorexia. It also has antitussive effects, and reduces the rewarding and analgesic effects of morphine, although it did not prevent the development of dependence. It has been shown to reduce alcohol self-administration in animals and suppressed relapses in animal models of alcoholism, and ORL-1 agonists may have application in the treatment of alcoholism. Ro64-6198 was able to be recognised as a discriminative stimulus by rats distinct from other opioid receptor ligands, but was not able to produce the conditioned place preference thought to be indicative of addictive potential. Consequently, while the role of ORL-1 receptors in the body is complex and remains poorly understood, Ro64-6198 has demonstrated multiple pharmacological actions and has been very useful in the study of the ORL-1 receptor system, especially in relation to anxiety and anorexia; however, due to poor oral bioavailability, Ro 64-6198 will most likely not be pursued clinically. Studies in primates showed it to have analgesic effects but without producing respiratory depression or reinforcing effects.
== Career == In December 1986, Cameron joined the Department of Chemical Engineering at the University of Wisconsin—Madison, as an assistant professor and advanced to full professor. The focus of his research was metabolic engineering (a field now more commonly known as synthetic biology) and industrial microbiology. One of his first projects was the engineering of the microbial pathway for 1,3-propanediol in Escherichia coli. This work was an early step in a process that was eventually commercialized by DuPont and Tate & Lyle. He is also the inventor of a process for the microbial production of 3-hydroxypropionic acid, which provides a bio-based route to industrial chemicals such as acrylic acid. In 1996 he did a sabbatical at the ETH Zurich (Switzerland) in the laboratory of James (Jay) E. Bailey. In 1998 he took a leave of absence to start the Biotechnology Development Center (BioTDC) at Cargill, Inc. in Minneapolis. In 2000 he officially left the University of Wisconsin. Cameron was at Cargill, Inc. from 1998 to 2006, where he was Director of Biotechnology and chief scientist. While at Cargill he worked closely with NatureWorks on the development of a low-pH process for lactic acid as a feedstock for polylactic acid. He and his team also worked with Cargill Ventures on deal-sourcing and due-diligence. In June 2006, Cameron moved from Cargill to join the newly formed Silicon Valley venture capital firm, Khosla Ventures, as chief scientific officer. In 2008, Cameron returned to the Midwest to help Piper Jaffray build and grow its clean tech investment business.
== Further reading == Hoffman, D.C., Ghiorso, A., Seaborg, G. T. The transuranium people: the inside story, (2000), 201–229 Morss, L. R., Edelstein, N. M., Fuger, J., The chemistry of the actinide and transactinide element, 3, (2006), 1630–1636 A Guide to the Elements – Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
For services to the community in Radley, Oxfordshire. Robert Frank Earl. For services to the community in Radley, Oxfordshire. Christopher Harry Wrenn Eaton. For services to the community in Wakes Colne, Essex. Euros Hefin Edwards. Watch Manager, Mid and West Wales Fire and Rescue Service. For services to Fire and Rescue. Greta Edwards. Cleaner and Kitchen Assistant, North Shore Academy, Stockton-on-Tees. For services to Education. Llinos Edwards. Lately Nurse Team Leader, The Looked After Children Team, Betsi Cadwaladr University Health Board. For services to Vulnerable Children in North Wales. Stephen David Elsden. Chief Executive, Compaid Trust. For services to Charity and to People with Disabilities. Robert Felix Erith TD DL. For services to the Environment in Dedham Vale, Essex and Suffolk. Sandra Mary Esqulant. For services to the community in Spitalfields, London Borough of Tower Hamlets. Annabel Whyte Evans. For services to the community in Chesham, Buckinghamshire. Lyndsey Claire Evans. For services to the community in South Wye, Herefordshire. Marian Louise Evans. For services to Business. Edward Everett. Member, Friends of Bridgwater Canal. For services to the Environment in Sale, Metropolitan Borough of Trafford. John Fielding. Scout Leader, 2nd Rishton Baptist Scout Group, Lancashire. For services to Young People and to the community in Lancashire. Mabel Elsie Finnigan. County Captain, Shropshire Ladies Bowls Team. For services to Bowls. Mary Margaret Rose Fisher. Lately Lollipop Crossing Patrol, Darley and Summerbridge Community Primary School, Harrogate.
Sources: en.wikipedia.org
Glutathione is a tripeptide of three amino acids: glutamate, cysteine, and glycine. The cysteine residue provides the sulfhydryl group that gives the molecule its reducing properties.
GSH is the reduced form, which contains a free sulfhydryl group. GSSG is the oxidized form, formed when two GSH molecules join through a disulfide bond. The ratio of GSH to GSSG is often used to assess cellular redox status.
No, glutathione is synthesized endogenously in most cells. It is not classified as an essential nutrient because the body can produce it from amino acid precursors. Dietary sources exist, but they are not required to maintain life.
Common methods include enzymatic recycling assays, liquid chromatography, and mass spectrometry. Many protocols separate reduced glutathione from its oxidized disulfide form before detection.