Tietze assay is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-05-13. Where a claim depends on a specific study, the study is described rather than over-claimed.
Interpreting glutathione measurements requires attention to pre-analytical variables. The GSSG concentration in a sample can rise artificially during storage or processing, making the GSH/GSSG ratio unreliable if not controlled. Reference ranges vary by specimen type, assay, and population, so comparisons across studies are difficult. Plasma glutathione is low and sensitive to hemolysis, while whole blood reflects primarily erythrocyte content. Many studies measure total glutathione rather than the reduced and oxidized forms separately, which limits conclusions about redox status.
Accurate measurement of glutathione begins with careful sample handling. Because GSH oxidizes rapidly to GSSG, samples must be processed quickly or frozen immediately. Acid precipitation with metaphosphoric acid or perchloric acid is common; it lowers pH, precipitates proteins, and helps preserve the reduced form. Chelating agents such as EDTA can limit metal-catalyzed oxidation. For whole blood, hemolysis releases glutathione from erythrocytes, so plasma and serum values differ substantially from whole blood values.
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.
| Property | Value | Notes |
|---|---|---|
| Common analytical method | LC-MS/MS or HPLC | Separation of GSH and GSSG |
| Limit of detection | Nanomolar range | Method dependent |
| Typical sample storage | -80 °C | For biological matrices |
| Common reducing agent | TCEP or DTT | Prevents oxidation during processing |
| Common synonym | Gamma-glutamylcysteinylglycine | Systematic name |
Cells synthesize glutathione through two ATP-dependent steps: glutamate-cysteine ligase joins glutamate and cysteine, and glutathione synthetase adds glycine to form the complete tripeptide. Breakdown occurs through gamma-glutamyl transpeptidase and subsequent peptidase reactions, forming the gamma-glutamyl cycle. Within cells, glutathione also forms a disulfide-linked dimer called GSSG when two GSH molecules react. The balance between GSH and GSSG is widely used as an indicator of oxidative conditions, although the ratio can vary by compartment and tissue.
Glutathione supports several cellular processes beyond direct antioxidant action. It serves as a cofactor for glutathione peroxidase and glutathione S-transferase enzymes, which reduce peroxides and conjugate electrophiles, respectively. The molecule also acts as a reservoir of cysteine, an amino acid that can limit protein synthesis and redox signaling. In human nutrition, oral glutathione is sold as a supplement, but how much intact glutathione reaches tissues after ingestion remains an active research question. Clinical claims about supplementation are not uniformly supported by controlled trials.
Glutathione is a small tripeptide built from glutamic acid, cysteine, and glycine. Its peptide bond between glutamate and cysteine involves the gamma-carboxyl group rather than the usual alpha-carboxyl group. This structure gives the molecule a reactive thiol on the cysteine residue. The reduced form, often abbreviated GSH, is the predominant intracellular species in many cell types. Because the thiol can donate electrons, glutathione participates in redox chemistry and in the conjugation of reactive molecules.
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.
Biosynthesis proceeds in two ATP-dependent steps. First, glutamate-cysteine ligase joins glutamate and cysteine. Second, glutathione synthetase adds glycine to the intermediate. The pathway is regulated by cysteine availability, enzyme expression, and feedback inhibition by glutathione itself. Liver tissue has a particularly high capacity for synthesis and export. Because the molecule is made inside cells, circulating glutathione reflects a balance of release, uptake, and breakdown rather than simple dietary supply.
Functionally, glutathione supports redox balance by donating electrons and becoming oxidized. It also serves as a cofactor for enzymes such as glutathione peroxidases and glutathione S-transferases. These enzymes participate in peroxide reduction and in conjugation reactions that help process reactive molecules. Separate from antioxidant roles, glutathione can modify protein cysteines through S-glutathionylation, influencing enzyme activity and signaling. Research continues to examine how these chemical roles translate into whole-organism effects.
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.
== History == Evidence for periostitis found in the fossil record is studied by paleopathologists, specialists in ancient disease and injury. Periostitis has been seen in the late Cretaceous-Eocene crocodile Borealosuchus formidabilis, once known as Leidyosuchus. In one study, periostitis was the most common pathology in this species, with 134 instances of the condition out of 7,154 bones the scientists examined showing evidence for the condition. Periostitis has also been documented in dinosaurs, including a forelimb referred to as the long-necked Camarasaurus grandis, as well as the shoulder blade of a horned dinosaur.
Boron neutron capture therapeutics are pharmaceuticals intended for use to deliver boron-10 to cancerous cells as part of boron neutron capture therapy (BNCT). Boron-10 atoms strongly absorb neutrons to form a metastable state of boron-11, which undergoes α-decay. By accumulating boron-10 in cancerous cells and subjecting the tumor to neutron radiation, high-energy α particles are selectively delivered only to the target cells. This neutron bombardment results in the selective destruction of the tumor cells that the boron-10 was absorbed into. As of 2023, the technology is available in Japan only, and even there few implementations have been reported.
Molybdenum is a chemical element; it has symbol Mo and atomic number 42. The name is derived from Ancient Greek μόλυβδος mólybdos, meaning lead, since its ores were sometimes confused with those of lead. Molybdenum minerals have been known throughout history, but the element was discovered (in the sense of differentiating it as a new entity from the mineral salts of other metals) in 1778 by Carl Wilhelm Scheele. The metal was first isolated in 1781 by Peter Jacob Hjelm. Molybdenum does not occur naturally as a free metal on Earth; in its minerals, it is found only in oxidized states. The free element, a silvery metal with a grey cast, has the sixth-highest melting point of any element. It readily forms hard, stable carbides in alloys, and for this reason most of the world production of the element (about 80%) is used in steel alloys, including high-strength alloys and superalloys. Most molybdenum compounds have low solubility in water. Heating molybdenum-bearing minerals under oxygen and water affords molybdate ion MoO2−4, which forms quite soluble salts. Industrially, molybdenum compounds (about 14% of world production of the element) are used as pigments and catalysts. Molybdenum-bearing enzymes are by far the most common bacterial catalysts for breaking the chemical bond in atmospheric molecular nitrogen in the process of biological nitrogen fixation. At least 50 molybdenum enzymes are now known in bacteria, plants, and animals, although only bacterial and cyanobacterial enzymes are involved in nitrogen fixation.
On 10 January 1973, negotiations broke down when Kissinger demanded the release of all American POWs in North Vietnam once a peace agreement was signed, but offered no guarantees about Viet Cong prisoners being held in South Vietnam. Tho stated: "I cannot accept your proposal. I completely reject it". Tho wanted the release of all prisoners once a peace agreement was signed, which led Kissinger to say this was an unreasonable demand. Tho, who had been tortured as a young man by the French colonial police for advocating Vietnamese independence, shouted: "You have never been a prisoner. You don't understand suffering. It's unfair". Kissinger finally offered the concession that the United States would use "maximum influence" to pressure the South Vietnamese government to release all Viet Cong prisoners within sixty days of a peace agreement being signed. Thiệu once again rejected the peace agreement, only to receive an ultimatum from Nixon: "You must decide now whether you desire to continue our alliance or whether you want me to seek a settlement with the enemy which serves U.S. interests alone". Nixon told Kissinger: "Brutality is nothing. You have never seen it if this son-of-a-bitch doesn't go along, believe me". Nixon's threat served its purpose, and Thiệu reluctantly accepted the peace agreement. On 23 January 1973, at 12:45 pm, Kissinger and Tho signed a peace agreement in Paris that called for the complete withdrawal of all U.S. forces from Vietnam by March in exchange for North Vietnam freeing all the U.S. POWs.
The expected results for external quality assessment samples are not disclosed to the laboratory. External quality assessment programs have been widely adopted in North America and western Europe, and laboratories are often required to participate in these programs to maintain accreditation. Logistical issues may make it difficult for laboratories in under-resourced areas to implement external quality assessment schemes.
Sources: en.wikipedia.org
=== Pharmacodynamics === The 3,6-diesters of morphine are drugs with more rapid and complete central nervous system penetration due to increased lipid solubility and other structural considerations. The prototype for this subgroup of semi-synthetic opiates is heroin and the group also includes dipropanoylmorphine, diacetyldihydromorphine, disalicylmorphine and others. Whilst this produces an enhanced "bang", i.e. a faster and more sudden onset of action when the drug is administered intravenously, it cannot be distinguished from morphine via other routes, although the different side effect profile, including lower incidence of nausea, is very apparent.
3,4-Dimethoxybenzaldehyde (veratraldehyde) → 3,4-Dimethoxycinnamic acid → 3,4-Dimethoxyphenylpropionic acid → 3,4-Dimethoxyphenylpropionamide → 3,4-Dimethoxyphenethylamine A much shorter synthesis is given by Shulgin and Shulgin.
H. Lundbeck Novo LEO Pharma Coloplast Dansac (owner Hollister Inc) Novozymes Pharma Nord Pharmacosmos ALK-Abelló Genmab RosePharma Santaris Pharma A/S Veloxis Pharmaceuticals Zealand Pharma Retail Salling Group (retail business) Coop Danmark, (part of the multi-sector Coop amba, formerly known as FDB until 2013) Dagrofa Transport A. P. Moller-Maersk Group (Maersk – conglomerate: shipping) Blue Water Shipping DFDS DSV Scan Global Logistics USTC (conglomerate: shipping, trading) Miscellaneous ISS (facility services) The Lego Group, as of 2014 the world's largest toy manufacturer by sales (in the first half of 2015, it made $2.1 billion in sales) Terma A/S, aerospace and defense
1977: Argentine-Canadian scientist Veronica Dahl became the first graduate at Université d'Aix-Marseille II (and one of the first women in the world) to earn a PhD in artificial intelligence. 1977: Canadian-American Elizabeth Stern published her research on the link between birth control pills – which contained high levels of estrogen at the time – and the increased risk of cervical cancer development in women. Her data helped pressure the pharmaceutical industry into providing safer contraceptive pills with lower hormone doses. 1977: Janina Oszast is among the first Polish palaeobotanists attempting biogeographic synthesis of Miocene land sediments. She was also the first person in Poland to identify pollen from a range of herbaceous plants and the first to find pollen grains of Ephedra in glaciation period deposits. 1978: Anna Jane Harrison became the first female president of the American Chemical Society. 1978: American biochemist Mildred Cohn served as the first female president of the American Society for Biochemistry and Molecular Biology, then called the American Society of Biological Chemists.
Sources: en.wikipedia.org
The scalp is the area of the head where head hair grows. It is made up of skin, layers of connective and fibrous tissues, and the membrane of the skull. Anatomically, the scalp is part of the epicranium, a collection of structures covering the cranium. The scalp is bordered by the face at the front, and by the neck at the sides and back. The scientific study of hair and scalp is called trichology.
Tramadol, sold under the brand name Tramal among others, is an opioid pain medication and a serotonin–norepinephrine reuptake inhibitor (SNRI) used to treat moderate to severe pain. When taken by mouth in an immediate-release formulation, the onset of pain relief usually begins within an hour. It is also available by injection. It is available in combination with paracetamol (acetaminophen). As is typical of opioids, common side effects include constipation, itchiness, and nausea. Serious side effects may include hallucinations, seizures, increased risk of serotonin syndrome, decreased alertness, and drug addiction. A change in dosage may be recommended in those with kidney or liver problems. It is not recommended in those who are at risk of suicide or in those who are pregnant. While not recommended in women who are breastfeeding, those who take a single dose should not generally have to stop breastfeeding. Tramadol is converted in the liver to O-desmethyltramadol (desmetramadol), an opioid with a stronger affinity for the μ-opioid receptor. Tramadol was patented in 1972 and launched under the brand name Tramal in 1977 by the West German pharmaceutical company Grünenthal GmbH. In the mid-1990s, it was approved in the United Kingdom and the United States. It is available as a generic medication and marketed under many brand names worldwide. In 2023, it was the 36th most commonly prescribed medication in the United States, with more than 16 million prescriptions.
=== Brain nonsynaptic glutamatergic signaling circuits === Extracellular glutamate in Drosophila brains has been found to regulate postsynaptic glutamate receptor clustering, via a process involving receptor desensitization. A gene expressed in glial cells actively transports glutamate into the extracellular space, while, in the nucleus accumbens-stimulating group II metabotropic glutamate receptors, this gene was found to reduce extracellular glutamate levels. This raises the possibility that this extracellular glutamate plays an "endocrine-like" role as part of a larger homeostatic system.
The project was suggested to and given the green light by Mazda's Senior Managing Director Keiji Asano while he was on a trip to Indonesia in 1986. Sold alongside the seventh generation 323, an MR90 cost less than half the price of the newer model, but still more expensive than Toyota Kijang and Suzuki Carry "minibuses" as the country imposed 30% tax for saloons. In the past hatchback and wagon were classified as sedan Indonesia, but then revised as "minibus" in early 2000s. This changes boosting the sales of hatchbacks and started the downfall of sedans popularity in Indonesia.
This effect is called herd immunity. Polio, which is transmitted only among humans, is targeted by an extensive eradication campaign that has seen endemic polio restricted to only parts of three countries (Afghanistan, Nigeria, and Pakistan). However, the difficulty of reaching all children, cultural misunderstandings, and disinformation have caused the anticipated eradication date to be missed several times. Vaccines also help prevent the development of antibiotic resistance. For example, by greatly reducing the incidence of pneumonia caused by Streptococcus pneumoniae, vaccine programs have greatly reduced the prevalence of infections resistant to penicillin or other first-line antibiotics.
Sources: en.wikipedia.org
Glutathione oxidizes quickly when cells are disrupted or when samples sit at room temperature. Rapid processing or immediate freezing minimizes the conversion of GSH to GSSG. This step helps ensure that the measured ratio reflects the original biological state.
The Tietze assay is an enzymatic recycling method that measures total glutathione. It uses glutathione reductase to reduce GSSG back to GSH, which then reacts with a chromogen or fluorophore. The reaction cycles repeatedly, amplifying the signal for detection.
Yes, but the choice of blood fraction matters. Plasma or serum contains low glutathione levels and is easily affected by hemolysis. Whole blood mainly reflects the high glutathione content of erythrocytes, so results from different fractions are not directly comparable.
The ratio depends on rapid separation or blocking of GSH before oxidation occurs. GSSG can be formed ex vivo if samples are not processed quickly in cold, acidic conditions. Even small delays can shift the apparent ratio, making standardized protocols essential.