If you have been reading about derivatization 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 2026-07-04. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Recommended storage | −20 °C, desiccated | For dry powder; limit light and air exposure |
| Solution stability | Hours to days at neutral pH | Faster loss at warm, alkaline, or oxygen-rich conditions |
| Routine measurement | LC-MS/MS or HPLC | Enzymatic recycling assays measure total glutathione |
| Thiol pKa | About 8.7 | The thiolate form reacts with oxidants and electrophiles |
| Common abbreviations | GSH and GSSG | GSSG is the disulfide-linked dimer |
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.
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.
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.
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.
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.
In January 2001, Lee, Lifeson, and Peart came together to attempt to reassemble the band. According to Peart, "We laid out no parameters, no goals, no limitations, only that we would take a relaxed, civilized approach to the project." With the help of producer Paul Northfield, the band produced seventy-four minutes of music for their new album Vapor Trails, which was written and recorded in Toronto. Vapor Trails marked the first Rush studio recording to not include any keyboards or synthesizers since Caress of Steel. According to the band, the album's developmental process was extremely taxing and took approximately 14 months to finish, the longest they had ever spent writing and recording a studio album. Vapor Trails was released on May 14, 2002; to herald the band's comeback, the single and lead track from the album, "One Little Victory", was designed to grab the attention of listeners with its rapid guitar and drum tempos. The album was supported by the band's first tour in six years, including first-ever concerts in Brazil and Mexico City, where they played to some of the largest crowds of their career. The largest was a capacity crowd of 60,000 in São Paulo. Vapor Trails peaked at No. 3 in Canada and No. 6 in the US, while selling disappointingly in the UK, where it peaked at No. 38.
== Academic career == In 1974, Candace Pert earned a Ph.D. in pharmacology from Johns Hopkins University School of Medicine, where she worked in the laboratory of Solomon Snyder and discovered the brain's opiate receptor. Pert conducted a National Institutes of Health Postdoctoral Fellowship with the Department of Pharmacology at the Johns Hopkins University School of Medicine from 1974 to 1975. She conducted research at the National Institute of Mental Health from 1975 to 1987. In 1983, she became the Chief of the Section on Brain Biochemistry of the Clinical Neuroscience Branch, the only female chief at NIMH. She left to found and direct a private biotech laboratory in 1987. Pert was a research professor in the department of physiology and biophysics at Georgetown University School of Medicine in Washington, D.C. In her latter years, she was with RAPID Pharmaceuticals. In 1997 she published her book Molecules of Emotion. She appeared as one of the experts in Bill Moyers 1993 PBS video production, "Healing and the Mind", and in the 2004 film What the #$*! Do We Know!?. She died on September 12, 2013, in Potomac, Maryland.
The gallbladder is a hollow pear-shaped organ located posterior to the inferior middle part of the right lobe of the liver. It is variable in shape and size. It stores bile before it is released into the small intestine via the common bile duct to help with digestion of fats. It receives bile from the liver via the cystic duct, which connects to the common hepatic duct to form the common bile duct. The gallbladder gets its blood supply from the cystic artery, which in most people, emerges from the right hepatic artery. Gallstone is a common disease in which one or more stones form in the gallbladder or biliary tract. Most people are asymptomatic but if a stone blocks the biliary tract, it causes a gallbladder attack; symptoms may include sudden pain in the upper right abdomen or center of the abdomen. Nausea and vomiting may also occur. Typical treatment is removal of the gallbladder through a procedure called a cholecystectomy. Having gallstones is a risk factor for gallbladder cancer, which, although quite uncommon, is rapidly fatal if not diagnosed early.
=== Discontinued === Alniditan (R-91274) – serotonin 5-HT1B and 5-HT1D receptor agonist – migraine [72] Avitriptan (BMS-180048) – serotonin 5-HT1B and 5-HT1D receptor agonist and triptan – migraine [73] Bezisterim (HE-3286; NE-3107; Triolex; 17α-ethynyl-5-androstene-3β,7β,17β-triol) – undefined mechanism of action (synthetic androstenetriol analogue and anti-inflammatory) – migraine [74] BI-44370 (BI44370) – calcitonin gene-related peptide receptor (CGRPR) antagonist – migraine [75] Botulinum toxin A topical (RT-001) – acetylcholine release inhibitor and neuromuscular blocking agent – migraine [76] Carisbamate (Comfyde; JNJ-10234094; RWJ-333369; YKP-509) – unknown mechanism of action – migraine [77] Dasolampanel (NGX-426) – ionotropic glutamate AMPA and kainate receptor antagonist – migraine [78] Dextromethorphan/quinidine (DXM/Q; AVP-923; Neurodex; Nuedexta; Zenvia) – combination of dextromethorphan (various actions) and quinidine (various actions) – migraine [79] Dihydroergocryptine (SRN-001) – non-selective monoamine receptor modulator and ergoline – migraine [80] Donitriptan (F-11356) – serotonin 5-HT1B and 5-HT1D receptor agonist and triptan – migraine [81] Dotarizine (Dotaricin; FI-6026) – calcium channel blocker and serotonin 5-HT1A, 5-HT2A, and 5-HT2C receptor antagonist – migraine [82] Dronabinol (Δ9-THC; Δ9-tetrahydrocannabinol; Deltanyne; Elevat; Marinol) – cannabinoid CB1 and CB2 receptor agonist – migraine [83] Ergotamine inhalation (Tempo-ergotamine) – non-selective monoamine receptor modulator and ergoline – migraine [84] Esprolol ((S)-ACC-9369) – beta blocker (β-adrenergic receptor antagonist) (amoxolol prodrug) – migraine [85] Ethinylestradiol/levonorgestrel (DP3; DR-103; DR-105; LoSeasonique; Seasonique) – combination of ethinylestradiol (an estrogen) and levonorgestrel (a progestogen) and a combined oral contraceptive – menstrual migraine [86] (S)-Ethylisothiouronium diethylphosphate (Difetur; MTR-104; MTR-105; MTR-106; MTR-107; MTR-108; Raviclust; Ravimig; Raviten) – nitric oxide synthase (NOS) inhibitor [87] Fremanezumab (Ajovy; LBR-101; PF-04427429; PF-4427429; RN-307; TEV-48125) – monoclonal antibody against calcitonin gene-related peptide (CGRP) – cluster headache, headache [88] Gabapentin (CI-945; Gabapen; GOE-3450; Neurontin) – gabapentinoid (α2δ subunit-containing voltage-gated calcium channel ligand) – migraine [89] Gabapentin enacarbil (1838262; ASP8825; GSK-1838262; Horizant; Regnite; Solzira; XP13512) – gabapentinoid (α2δ subunit-containing voltage-gated calcium channel ligand) – migraine [90] Ganaxolone (CCD-1042; Ztalmy) – GABAA receptor positive allosteric modulator and neurosteroid – migraine [91] HTL-0022562 (BHV-3100; HTL-22562) – calcitonin gene-related peptide receptor (CGRPR) antagonist – migraine [92] IS-159 – serotonin 5-HT1B and 5-HT1D receptor agonist – migraine [93] Lacosamide (ADD-234037; Erlosamide; Harkoseride; SPM-927; SPM-929; Vimpat; Vimpato) – various actions – migraine [94] Lanepitant (LY-303870) – neurokinin NK1 receptor antagonist – migraine [95] Lidocaine transdermal patch (ADL-87223; LidoPAIN) – sodium channel blocker – headache [96] Lornoxicam (Bosporon; Chlortenoxicam; HN-10000; RO-139297; Safem; TS-110; Xefo) – COX inhibitor/NSAID – migraine [97] LY-2300559 – metabotropic glutamate receptor 2 (mGluR2) positive allosteric modulator and cysteinyl leukotriene receptor 1 (CysLTR1) antagonist – migraine [98] LY-334370 – serotonin 5-HT1F receptor agonist and triptan – migraine [99] MEDI-0618 – monoclonal antibody against protease-activated receptor 2 (PAR2) – migraine [100] Olcegepant (BIBN-4096; BIBN-4096BS) – calcitonin gene-related peptide receptor (CGRPR) antagonist – migraine [101] Oxytocin (TI-001; TI-114; TNX-1900; TNX-2900) – oxytocin receptor agonist – migraine [102] Perampanel (E-2007; ER-155055-90; Fycompa) – AMPA receptor antagonist – migraine [103] PF-5180999 (PF-05180999) – phosphodiesterase PDE2 inhibitor – migraine [104] PNU-142633 (PNU-142633F) – serotonin 5-HT1D receptor agonist – cluster headache, headache, migraine [105] Prochlorperazine inhalation (AZ-001) – typical antipsychotic (non-selective monoamine receptor modulator) – migraine [106] Propisergide (ergalgin) – serotonin receptor modulator and ergoline – migraine Propofol phosphate (Neuprox; propofol prodrug) – GABAA receptor positive allosteric modulator (propofol prodrug) – migraine [107] Research programme: migraine therapy - Orexo (OX-40; OX641) – undefined mechanism of action – migraine [108] Selurampanel (BGG-492; BGG-492A) – ionotropic glutamate AMPA and kainate receptor antagonist – migraine [109] Sergolexole (LY-281067) – serotonin 5-HT2 receptor antagonist and ergoline – migraine [110] Telcagepant (MK-0974) – calcitonin gene-related peptide receptor (CGRPR) antagonist – migraine [111] Tezampanel (LY-293558; NGX-424; PRN-001-01) – ionotropic glutamate AMPA and kainate receptor antagonist – migraine [112] Tizanidine (AN-021A; AN-021; DS-103282; Sirdalud; Ternelin; Zanaflex) – α2-adrenergic receptor agonist – migraine [113] Tonabersat (SB-220453; USL-260; Xiflam) – connexin 43 (GJA1) inhibitor – migraine [114] Zolmitriptan inhalation (CVT-427) – serotonin 5-HT1B and 5-HT1D receptor agonist and triptan – migraine [115] Zonisamide (AD-810; CI-912; Excegran; Kinaplase; PD-110843; Tremode; Trerief; Zonegran) – calcium channel blocker, sodium channel blocker, and other actions – migraine [116]
Sources: en.wikipedia.org
=== 15 December === President Zelenskyy stated that Russia should start to withdraw their troops by Christmas as a step to end the conflict. Russia responded that there would be "No Christmas Ceasefire" until Ukraine accepted its loss of territory. The Kyiv School of Economics published a report estimating that, as of November 2022, Russia's invasion had caused $136 billion in direct damage to Ukraine's infrastructure. Energy infrastructure, industry, public, and private enterprises were impacted the most. USAID delivered four excavators and over 130 generators to Kyiv for use in "boiler houses and heat supply stations" according to mayor Vitali Klitschko. The recently liberated city of Kherson was entirely without power following Russian shelling, which killed at least two people. The Kherson military administration stated that the city was hit 86 times with "artillery, MLRS, tanks, mortars and UAVs," in the past 24 hours. In the Donbas, Ukrainian forces bombarded Donetsk in the largest wave of shelling seen since 2014, according to mayor Alexey Kulemzin. Volker Türk, the United Nations High Commissioner for Human Rights, published a detailed summary of 441 killings including 8 girls during the conflict. The United States expanded its training to 500 Ukrainians each month at Germany.
Hematocrit measurements had previously been described in the literature, but Wintrobe's method differed in that it used a large tube that could be mass-produced to precise specifications, with a built-in scale. The fraction of red blood cells in the tube was measured after centrifugation to determine the hematocrit. The invention of a reproducible method for determining hematocrit values allowed Wintrobe to define the red blood cell indices.
=== From aldehydes === The Tishchenko reaction involves disproportionation of an aldehyde in the presence of an anhydrous base to give an ester. Catalysts are aluminium alkoxides or sodium alkoxides. Benzaldehyde reacts with sodium benzyloxide (generated from sodium and benzyl alcohol) to generate benzyl benzoate. The method is used in the production of ethyl acetate from acetaldehyde.
Sources: en.wikipedia.org
== History == The first acknowledged case of obesity-related non-alcoholic fatty liver was observed in 1952 by Samuel Zelman. Zelman started investigating after observing a fatty liver in a hospital employee who drank more than twenty bottles of Coca-Cola a day. He then went on to design a trial for a year and a half on 20 people with obesity who did not have alcohol use disorder, finding that about half of them had substantially fatty livers. Fatty liver was, however, linked to diabetes since at least 1784 — an observation picked up again in the 1930s. Studies in experimental animals implicated choline inadequacy in the 1920s and excess sugar consumption in 1949. The name "non-alcoholic steatohepatitis" (NASH) was later defined in 1980 by Jurgen Ludwig and his colleagues from the Mayo Clinic to raise awareness of the existence of this pathology, as similar reports previously were dismissed as "patients' lies". This paper was mostly ignored at the time but eventually came to be seen as a landmark paper, and starting in the mid-1990s, the condition began to be intensively studied, with a series of international meetings being held on the topic since 1998. The broader NAFLD term started to be used around 2002. Diagnostic criteria began to be worked out, and in 2005 the Pathology Committee of the NIH NASH Clinical Research Network proposed the NAS scoring system. In 2023, a global consensus panel composed mostly of hepatology researchers and clinicians recommended a change of name to metabolic dysfunction–associated steatotic liver disease (MASLD).
3,4-Ethylenedioxythiophene (EDOT) is an organosulfur compound with the formula C2H4O2C4H2S. The molecule consists of thiophene, substituted at the 3 and 4 positions with an ethylene glycolyl unit. It is a colorless viscous liquid. EDOT is the precursor to the polymer PEDOT, which is found in electrochromic displays, photovoltaics, electroluminescent displays, printed wiring, and sensors.
Although all anabolic steroids have androgenic effects, some of them paradoxically results in feminization, such as breast tissue in males, a condition called gynecomastia. These side effects are caused by the natural conversion of testosterone into estrogen and estradiol by the action of aromatase enzyme, encoded by the CYP19A1 gene. Prolonged use of androgenic-anabolic steroids by men results in temporary shut down of their natural testosterone production due to an inhibition of the hypothalamic–pituitary–gonadal axis. This manifests in testicular atrophy, inhibition of the production of sperm, sexual function and infertility. A short (1–2 months) use of androgenic-anabolic steroids by men followed by a course of testosterone-boosting therapy (e.g. clomifene and human chorionic gonadotropin) usually results in return to normal testosterone production.)
ABRF 2025, 23–28 March 2025, Las Vegas, NV ABRF 2024, 21–24 April 2024, Minneapolis, MN ABRF 2023, 7–10 May 2023, Boston, MA ABRF 2022, 27–30 March 2022, Palm Springs, CA ABRF 2021, 7–11 March 2021, virtual meeting due to COVID-19 ABRF 2020, 29 February – 3 March 2020, Palm Springs, CA ABRF 2019, 23–26 March, San Antonio, Texas; 30 Years of Challenging the Limits of Science and Technology, Opening Doors for the Future ABRF 2018, 22–25 April, Myrtle Beach, South Carolina; The Premier Conference for Core Services ABRF 2017, 25–28 March, San Diego, California; A Forum for Advancing Today's Core Technologies to Enable Tomorrow's Innovations ABRF 2016, 20–23 February, Ft. Lauderdale, Florida; Innovative Technologies Accelerating Discovery ABRF 2015, 28–31 March, St.
Sources: en.wikipedia.org
Common approaches include enzymatic recycling assays, HPLC, and LC-MS/MS. Acid extraction and rapid processing limit oxidation before analysis.
Reduced glutathione oxidizes easily and can change after collection. Delays, warmth, light, and repeated freezing can alter measured values.
Labels may state total glutathione without specifying reduced and oxidized content. Purity, counterions, and actual assay can vary between products.
Pre-analytical handling, extraction chemistry, and detection method all influence reported glutathione values. Oxidation during sample processing can shift the measured GSH/GSSG ratio. Standardized protocols and reference materials help reduce, but do not eliminate, these differences.