If you have been reading about Tietze assay 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 2026-04-16. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| 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. |
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.
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.
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.
Laboratory measurement of glutathione requires attention to oxidation before analysis. Blood, tissue, or cell samples can lose reduced glutathione as it converts to GSSG or forms mixed disulfides with proteins. Acid extraction, rapid freezing, and thiol-blocking reagents are common strategies to preserve the original distribution. Reported concentrations therefore depend on collection protocol, extraction method, and the time between sampling and analysis. Comparisons across studies are most reliable when these pre-analytical variables are described.
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.
Glutathione is most stable as a dry powder stored cool and dry, but its thiol group is readily oxidized in solution. Aqueous preparations at neutral or alkaline pH lose GSH faster because the thiolate form reacts with dissolved oxygen and metal ions. Acidic conditions, chelating agents, and oxygen exclusion can slow oxidation, while repeated freeze-thaw cycles promote degradation. Light exposure and trace metals also contribute to loss. Laboratories typically validate stability for their own matrices because degradation rates depend on pH, temperature, concentration, and container materials.
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.
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.
2-Hydroxy-4,5-methylenedioxymethamphetamine (6-hydroxy-3,4-methylendioxymethamphetamine) It is a non-neurotoxic metabolite of the drug 3,4-methylenedioxymethamphetamine, structurally related to 2-hydroxy-4,5-methylenedioxyamphetamine; it is detected in the brains and plasma of rats but not in their urine. It did not alter the levels of norepinephrine, glutathione, glial fibrillary acidic protein, or serotonin.
). The question raised but not answered by this study was whether the illness caused subtle immune deficiency that led to reactivation of HHV-6, or whether reactivation of HHV-6 led to the symptoms of the illness. Subsequent studies employing only serological techniques that do not distinguish active from latent infection have produced mixed results: most, but not all, have found an association between CFS and HHV-6 infection. Other studies have employed assays that can detect active infection: primary cell culture, PCR of serum or plasma, or IgM early antigen antibody assays. The majority of these studies have shown an association between CFS and active HHV-6 infection, although a few have not. In summary, active infection with HHV-6 is present in a substantial fraction of patients with CFS. Moreover, HHV-6 is known to infect cells of the nervous system and immune system, organ systems with demonstrable abnormalities in CFS. Despite this association, it remains unproven that reactivated HHV-6 infection is a cause of CFS.
de novo synthesis The assembly of a synthetic nucleic acid sequence from free nucleotides without relying on an existing template strand, i.e. de novo, by any of a variety of laboratory methods. De novo synthesis makes it theoretically possible to construct completely artificial molecules with no naturally occurring equivalent, and no restrictions on size or sequence. It is performed routinely in the commercial production of customized, made-to-order oligonucleotide sequences such as primers.
Sources: en.wikipedia.org
=== Subclinical hypothyroidism === There is no evidence of a benefit from treating subclinical hypothyroidism in those who are not pregnant, and there are potential risks of unnecessary overtreatment. Untreated subclinical hypothyroidism may be associated with a modest increase in the risk of coronary artery disease when the TSH is over 10 mIU/L. There may be an increased risk for cardiovascular death. A 2007 review found no benefit of thyroid hormone replacement except for "some parameters of lipid profiles and left ventricular function". There is no association between subclinical hypothyroidism and an increased risk of bone fractures, nor is there a link with cognitive decline. American guidelines recommend that treatment should be considered in people with symptoms of hypothyroidism, detectable antibodies against thyroid peroxidase, a history of heart disease, or are at an increased risk for heart disease if the TSH is elevated but below 10 mIU/L. American guidelines further recommend universal treatment (independent of risk factors) in those with TSH levels that are markedly elevated; above 10 mIU/L because of an increased risk of heart failure or death due to cardiovascular disease. NICE recommends that those with a TSH above 10 mIU/L should be treated in the same way as overt hypothyroidism. Those with an elevated TSH but below 10 mIU/L who have symptoms suggestive of hypothyroidism should have a trial of treatment but intend to stop this if the symptoms persist despite normalization of the TSH.
=== Modern sex determination methods === Recent developments in bioarchaeological methods have introduced more accurate and standardized techniques for sex estimation, especially when skeletal preservation is poor. Metric analyses of pelvic morphology using tools such as the Diagnose Sexuelle Probabiliste (DSP) method have achieved over 95% accuracy in adult individuals when analyzing the os coxae, using discriminant functions based on population-specific reference data. Geometric morphometric analyses of cranial and pelvic landmarks, particularly when paired with statistical classifiers or machine learning algorithms, have also shown high success rates in identifying sex across both forensic and archaeological samples. Molecular techniques have also become integrated into bioarchaeological practice. Ancient DNA (aDNA) shotgun sequencing enables near-perfect sex determination by quantifying X- and Y-chromosome reads, proving especially valuable when osteological indicators are absent or ambiguous. Where DNA preservation is insufficient, dental proteomics as detected amelogenin peptides in tooth enamel provide a minimally destructive and highly reliable alternative for sex estimation.
On May 20, 2008, Merck settled for $58 million with 30 states alleging that Merck engaged in deceptive marketing tactics to promote Vioxx. All its new television pain-advertisements must be vetted by the Food and Drug Administration and changed or delayed upon request until 2018.
As the head group forms such compact bicycle structure, the head group area is quite small relative to the big tail region consisting of 4 acyl chains. Based on this special structure, the fluorescent mitochondrial indicator, nonyl acridine orange (NAO) was introduced in 1982, and was later found to target mitochondria by binding to CL. NAO has a very large head and small tail structure which can compensate with cardiolipin's small head and large tail structure, and arrange in a highly ordered way. Several studies were published utilizing NAO both as a quantitative mitochondrial indicator and an indicator of CL content in mitochondria. However, NAO is influenced by membrane potential and/or the spatial arrangement of CL, so it's not proper to use NAO for CL or mitochondria quantitative studies of intact respiring mitochondria. But NAO still represents a simple method of assessing CL content.
Sources: en.wikipedia.org
== Extraction == β-glucan extraction from oat can be difficult due to tendency of depolymerization – which often occurs in high pH. Thus β-glucan extraction is usually performed under a more neutral pH and generally at temperatures of 60–100 °C (140–212 °F). Usually β-glucan is solubilized in the extraction process with residual starch, which is then removed by hydrolysis with alpha-amylase. The residual solution usually contains coextracts of hemicelluloses and proteins which can then be separated through selective precipitation. Through wet milling, sieving, and solvent-extraction, oat beta-glucans can achieve up to 95% extraction purity.
=== Christianised forms === Most of the Grail romances do not differ much from Perceval. The two pieces that hold particularly stronger Christian themes than prior works are the influential Vulgate and Post-Vulgate versions of the Queste del Saint Graal (featured in Malory's compilation) and the Sone de Nausay. The Queste del Saint Graal is heavily Christian not only in terms of the tone but also the characters and significant objects. The Grail maidens become angels, there is a constant relationship between the knights and religious symbolism; most importantly, the Fisher King is replicated as a priest-like figure. In the case of Sone de Nausay, Bron (the Fisher King) is part of a tale in which the story makes a constant correlation between the Gospel narrative and the history of the Grail.
Dorries eventually resigns on 26 August., 78 days after her initial announcement of "immediate effect". Boris Johnson's Resignation Honours are published. Highlights include knighthoods for Jacob Rees-Mogg and Simon Clarke, and a damehood for Priti Patel. The decision to award a life peerage to former special adviser Charlotte Owen is criticised due to her young age (29) and perceived lack of experience or contributions to British society. Johnson announces he will stand down as an MP with immediate effect after receiving the Commons Select Committee of Privileges's report into the Partygate scandal, triggering a by-election. 10 June Nigel Adams becomes the third Conservative MP in quick succession to stand down from Parliament with immediate effect, triggering a by-election. Temperatures reach above 30 °C for the first time since 24 August 2022, marking the hottest day of the year so far. Three guardsmen collapse during a military parade in London, due to the heat. Manchester City beat Inter Milan in the 2023 UEFA Champions League Final 1–0, with Rodri scoring the only goal to win the UEFA Champions League for the first time in their history. They become the second English team ever to win the Continental Treble after Manchester United in the 1998-99 Manchester United F.C. season, winning the FA Cup and the Premier League alongside the UEFA Champions League. 11 June Energy Secretary Grant Shapps, speaking on Sunday with Laura Kuenssberg, declares that the country "wants to move on" from Boris Johnson and dismisses claims the ex-PM was the victim of a "witch hunt".
1942: Native American aerospace engineer Mary Golda Ross became employed at Lockheed Aircraft Corporation, where she provided troubleshooting for military aircraft. She went on to work for NASA, developing operational requirements, flight plans, and a Planetary Flight Handbook for spacecraft missions such as the Apollo program. 1943: British geologist Eileen Guppy was promoted to the rank of assistant geologist, therefore becoming the first female geology graduate appointed to the scientific staff of the British Geological Survey. 1943: American geologist and crystallographer Elizabeth A. Wood became the first female to be hired as a member of the technical staff (MTS) at Bell Telephone Laboratories in Murray Hill, New Jersey. 1944: Indian chemist Asima Chatterjee became the first Indian woman to receive a doctorate of science, completing her studies at the University of Calcutta. She went on to establish the Department of Chemistry at Lady Brabourne College. 1945: American physicists and mathematicians Frances Spence, Ruth Teitelbaum, Marlyn Meltzer, Betty Holberton, Jean Bartik and Kathleen Antonelli programmed the electronic general-purpose computer ENIAC, becoming some of the world's first computer programmers.
The manufacture of immunoglobulins requires recombinase enzymes derived from the recombination activating genes RAG-1 and RAG-2. These enzymes are involved in the first stage of V(D)J recombination, the process by which segments of a B cell or T cell's DNA are rearranged to create a new T cell receptor or B cell receptor (and, in the B cell's case, the template for antibodies).Certain mutations of the RAG-1 or RAG-2 genes prevent V(D)J recombination, causing SCID.
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.
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.