This is a working overview of LC-MS/MS, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-06-16. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
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.
| 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 |
Common analytical approaches include enzymatic recycling assays, high-performance liquid chromatography, and mass spectrometry. The enzymatic recycling assay uses glutathione reductase and a colorimetric or fluorometric reagent to amplify signal, which gives good sensitivity for total glutathione. Chromatographic methods can separate GSH from GSSG and related thiols, while mass spectrometry offers structural confirmation and multiplexing. Each approach has different requirements for calibration, internal standards, and validation. No single method captures every form of glutathione in every matrix.
Storage recommendations for glutathione reagents usually specify a cool, dry, dark environment because the thiol oxidizes in air and light. Solid material is often kept desiccated at low temperature, while solutions are prepared fresh or stored frozen in aliquots. Repeated freeze-thaw cycles can accelerate degradation, and metal ions can catalyze oxidation. Quality control may include purity assays, water content, and identity confirmation. Stability limits are method-specific, so a stated shelf life applies only to defined conditions and packaging.
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.
Glutathione reference materials are sensitive to oxygen, light, and elevated temperature. Solid material is typically stored desiccated at -20 °C or below, while solutions require tighter control because thiol oxidation proceeds faster in liquid form. Aqueous solutions are often prepared fresh, kept cold, and protected from air; some protocols add acid or chelating agents to slow metal-catalyzed oxidation. Repeated freeze-thaw cycles can accelerate degradation and should be avoided. Stability data vary by matrix, so laboratories usually verify performance with their own storage conditions.
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.
Samples for glutathione analysis require careful handling because the compound oxidizes readily and can be consumed by enzymes after collection. Blood is often treated with acid or thiol-blocking agents soon after draw, and plasma should be separated quickly from red blood cells. Tissues are usually snap-frozen or extracted immediately. Aqueous solutions of glutathione are less stable than dry powder and degrade faster at neutral or alkaline pH, in light, or with dissolved oxygen. Repeated freeze-thaw cycles also reduce reliability.
Quality control for glutathione materials checks identity, assay, purity, water content, and disulfide content. Commercial products vary from research-grade powder to dietary supplements, and labels may not distinguish reduced from oxidized forms. In the United States, oral glutathione is commonly sold as a dietary supplement rather than an approved drug, while injectable forms fall under different rules and may require a prescription. Regulatory status differs by country. Analytical certificates, when available, help verify what a material contains, but independent testing remains important for interpretation.
Laboratory measurement of glutathione typically starts with rapid acid extraction to prevent oxidation and enzymatic degradation. Common methods include enzymatic recycling assays, high-performance liquid chromatography, and liquid chromatography coupled with mass spectrometry. The recycling assay uses glutathione reductase and a thiol-reactive colorimetric or fluorescent reagent, measuring total glutathione after converting disulfide forms. Chromatographic methods can separate reduced and oxidized forms, which helps when the redox ratio is the target. Choice of method affects sensitivity, specificity, and the amount of sample needed.
Archaeological evidence from sites in the United States, Mexico, and Peru indicates that mescaline-containing cacti have been used for over 6,000 years. Europeans recorded use of peyote in Native American religious ceremonies upon early contact with the Huichol people in Mexico. Other mescaline-containing cacti such as the San Pedro cactus have a long history of use in South America, from Peru to Ecuador. While religious and ceremonial peyote use was widespread in the Aztec Empire and northern Mexico at the time of the Spanish conquest, religious persecution confined it to areas near the Pacific coast and up to southwest Texas. However, by 1880, peyote use began to spread north of South-Central America with "a new kind of peyote ceremony" inaugurated by the Kiowa and Comanche people. These religious practices, incorporated legally in the United States in 1920 as the Native American Church, have since spread as far as Saskatchewan, Canada.
== Exposure == People may be exposed to PCP in occupational settings through the inhalation of contaminated workplace air and dermal contact with wood products treated with PCP. Also, general population exposure may occur through contact with contaminated environment media, particularly in the vicinity of wood-treatment facilities and hazardous-waste sites. In addition, some other important routes of exposure seem to be the inhalation of contaminated air, ingestion of contaminated ground water used as a source of drinking water, ingestion of contaminated food, and dermal contact with soils or products treated with the chemical.
In fungi, AAA is reduced to α‑aminoadipate-semialdehyde via AAA reductase (E.C 1.2.1.95) in a unique process involving both adenylation and reduction that is activated by a phosphopantetheinyl transferase (E.C 2.7.8.7). Once the semialdehyde is formed, saccharopine reductase (E.C 1.5.1.10) catalyses a condensation reaction with glutamate and NAD(P)H, as a proton donor, and the imine is reduced to produce the penultimate product, saccharopine. The final step of the pathway in fungi involves the saccharopine dehydrogenase (SDH) (E.C 1.5.1.8) catalysed oxidative deamination of saccharopine, resulting in L-lysine. In a variant AAA pathway found in some prokaryotes, AAA is first converted to N‑acetyl-α-aminoadipate, which is phosphorylated and then reductively dephosphorylated to the ε-aldehyde. The aldehyde is then transaminated to N‑acetyllysine, which is deacetylated to give L-lysine. However, the enzymes involved in this variant pathway need further validation.
Sources: en.wikipedia.org
250No In 2003, scientists at the FLNR reported that they had been able to synthesise 249No, which decayed by SF with a half-life of 54 μs. Further work in 2006 by scientists at the ANL showed that the activity was actually due to a K-isomer in 250No. The ground state isomer was also detected with a very short half-life of 3.7 μs.
==== Umeko ==== Koume Kodou (胡堂 小梅, Kodō Koume), also known as "Umeko" (ウメコ), is a ditzy, yet kind-hearted and perky, member of the team who serves as Deka Pink (デカピンク, Deka Pinku), though she frequently claims to be the field leader. Throughout the series, she spends every moment she can in a bubble bath with her three rubber ducks, Umeyo, Umenosuke, and Umegoro. After learning of Sen-chan's feelings for her, she moves in with him, as of the crossover film Mahō Sentai Magiranger vs. Dekaranger. As Deka Pink, Umeko wields the D-Knuckle and D-Stick, which can combine to form the D-Shot and allow her to perform the Twin Cam Shot alongside Jasmine. Using the SP License's Masquerade Mode (マスカレイドモード, Masukareido Mōdo), she can instantaneously change her outfit for disguise purposes. Umeko is portrayed by Mika Kikuchi (菊地 美香, Kikuchi Mika).
Nearly half a million speak other ancestral Southern varieties of Chinese, mainly Hokkien, Teochew, and Cantonese, as their home language, although the use of these is declining in favour of Mandarin or just English. Singapore Chinese characters are simplified characters. Singaporean English is largely based on British English, owing to the country's status as a former crown colony. However, forms of English spoken in Singapore range from Standard Singapore English to a colloquial form known as Singlish, which is discouraged by the government as it claims it to be a "bad language" that handicaps Singaporeans, presenting an obstacle to learning standard English and rendering the speaker incomprehensible to everyone except to another Singlish speaker. Standard Singapore English is fully understandable to all Standard English speakers, while most English-speaking people do not understand Singlish. Nevertheless, Singaporeans have a strong sense of identity and connection to Singlish, whereby the existence of Singlish is recognised as a distinctive cultural marker for many Singaporeans. As such, in recent times, the government has tolerated the diglossia of both Singlish and Standard English (only for those who are fluent in both), whilst continuously reinforcing the importance of Standard English amongst those who speak only Singlish (which is not mutually intelligible with the Standard English of other English-speaking countries).
Svarthöna, Bohuslän-Dals svarthöna, or Swedish Black Chicken is a Swedish landrace of domestic chickens that is considered to have originated from Ayam Cemani/Kadaknath breeds of chickens transported from Mozambique to Norway by sailors sometime in the 17th century. The Svarthöna has since adapted to a northerly climate, it but has retained the rare quality of black skin and connective tissue. The current form of Svarthöna has been given the status of a landrace. All Swedish entries in gene banks can be traced to a group of chickens that came to Sweden around the turn of the 19th century. In 1956, this flock was bought by two brothers in Bullarebygd. The Swedish Association for Landrace Breeds has preserved the Svarthöna in a gene bank since 1991. A rooster can weigh up to 2 kg, whilst hens do not exceed 1.5 kg. The eggs are small (38-48 g) with a large yolk. The Svarthöna has some flight ability. The black pigmentation found in skin and connective tissue has been shown to be caused by a variant of the gene EDN3, a trait shared with the Chinese Silkie, Indonesian Ayam Cemani, and Vietnamese Black H'Mong.
Sources: en.wikipedia.org
== Medical use == Tyrosine is a precursor to neurotransmitters and increases plasma neurotransmitter levels (particularly dopamine and norepinephrine), but has little if any effect on mood in normal subjects. A 2015 systematic review found that "tyrosine loading acutely counteracts decrements in working memory and information processing that are induced by demanding situational conditions such as extreme weather or cognitive load" and therefore "tyrosine may benefit healthy individuals exposed to demanding situational conditions".
== Landmark designations == Bryant Park and the New York Public Library Main Branch were jointly listed on the National Register of Historic Places (NRHP) in 1966. Its listing on the NRHP is distinct from the "New York Public Library" on the same day, which covered just the main branch building. In addition, in 1974, the New York City Landmarks Preservation Commission designated the park as a New York City scenic landmark.
Ramelteon, sold under the brand name Rozerem among others, is a melatonin agonist medication which is used in the treatment of insomnia. It is indicated specifically for the treatment of insomnia characterized by difficulties with sleep onset. It reduces the time taken to fall asleep, but the degree of clinical benefit is small. The medication is approved for long-term use. Ramelteon is taken by mouth. Side effects of ramelteon include somnolence, dizziness, fatigue, nausea, exacerbated insomnia, and changes in hormone levels. Ramelteon is an analogue of melatonin and is a selective agonist of the melatonin MT1 and MT2 receptors. The half-life and duration of ramelteon are much longer than those of melatonin. Ramelteon is not a benzodiazepine or Z-drug and does not interact with GABA receptors, instead having a distinct mechanism of action. Ramelteon was first described in 2002 and was approved for medical use in 2005. Unlike certain other sleep medications, ramelteon is not a controlled substance in nearly every country and has no known potential for misuse.
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.
Chromatographic methods can separate the two forms before detection. Enzymatic assays often measure total glutathione first and then use a separate procedure to estimate the oxidized fraction. The difference between total and oxidized amounts provides an indirect estimate of the reduced form.