The short version of LC-MS/MS fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-06-25. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
Several analytical methods can quantify glutathione, including high-performance liquid chromatography (HPLC) with UV or fluorescence detection for separating GSH and GSSG. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) offers higher specificity and sensitivity, often detecting nanomolar concentrations. The enzymatic recycling assay, often called the Tietze method, measures total glutathione by coupling reduction of GSSG to a colorimetric or fluorometric readout. Capillary electrophoresis and electrochemical detection are also used in specialized laboratories. Each method has distinct advantages and limitations regarding throughput, cost, and susceptibility to interference.
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.
| Property | Value | Notes |
|---|---|---|
| Typical assay | Enzymatic recycling assay (Tietze) | Measures total glutathione after reduction of GSSG. |
| Separation method | HPLC or LC-MS/MS | Can quantify GSH and GSSG separately with appropriate standards. |
| Solid storage | -20 °C, desiccated, protect from light | Dry powder is more stable than aqueous solutions. |
| Solution storage | Acidic pH, -80 °C, aliquot | Reduce oxygen exposure and freeze-thaw cycling. |
| Oxidation product | Glutathione disulfide (GSSG) | Formed by thiol oxidation; often measured as a stress marker. |
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.
Glutathione participates in detoxification reactions, amino acid transport, and the maintenance of protein thiols. It serves as a cofactor for several enzymes, including glutathione peroxidases and glutathione S-transferases. In research literature, altered glutathione status appears in studies of aging, infection, metabolic stress, and environmental exposure. Whether low glutathione is a cause, consequence, or marker of such conditions often remains unresolved. Direct measurement in blood or tissue provides a snapshot, but results depend on sample handling, timing, and the method used.
Glutathione is a small tripeptide made of glutamic acid, cysteine, and glycine. Its cysteine thiol group allows reversible oxidation and reduction, making it central to cellular redox chemistry. The reduced form, often abbreviated GSH, predominates inside most cells, while the oxidized disulfide form, GSSG, forms when two GSH molecules react. The ratio of GSH to GSSG is widely used as an indicator of oxidative stress in laboratory research, though it does not by itself diagnose a clinical condition.
Biosynthesis occurs in two ATP-dependent steps. The enzyme glutamate-cysteine ligase joins glutamate and cysteine, forming gamma-glutamylcysteine; glutathione synthetase then adds glycine to produce the complete tripeptide. Because the peptide bond from glutamate uses the gamma-carboxyl group, glutathione resists digestion by many ordinary peptidases. Tissues vary in synthesis capacity, and the liver generally contains high concentrations relative to many other organs. This uneven distribution contributes to organ-specific differences in redox buffering and affects how experimental results are interpreted across tissue types.
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.
Synthesis occurs in two ATP-dependent steps. The enzyme glutamate-cysteine ligase joins glutamate and cysteine to form gamma-glutamylcysteine, and glutathione synthetase adds glycine. The first step is rate-limiting and is influenced by cysteine availability and feedback inhibition by GSH. Breakdown involves gamma-glutamyl transferase and subsequent peptidases, which release constituent amino acids for reuse. Because turnover differs among tissues, measurements from blood, plasma, and tissues are not directly interchangeable. Research continues to clarify how compartment-specific pools are regulated in health and disease.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. It contains an unusual gamma-glutamyl bond between glutamate and cysteine, which resists cleavage by many peptidases. The reduced form, GSH, carries a thiol group on cysteine and is the dominant intracellular form in most cells. Its structure allows it to participate in redox reactions and to serve as a sulfur donor. The oxidized form, GSSG, consists of two GSH molecules joined by a disulfide bond.
In cells, glutathione helps maintain the reducing environment of the cytosol and supports enzymes that counteract reactive oxygen species. It acts as a cofactor for glutathione peroxidases, which reduce hydrogen peroxide and lipid peroxides, and for glutathione S-transferases, which conjugate electrophiles. The ratio of GSH to GSSG is often used as an indicator of oxidative stress, although the ratio can vary by compartment and cell type. Glutathione also stores cysteine, an amino acid that can be limiting for protein synthesis and antioxidant defense.
Novo Nordisk has also developed a genetically engineered insulin independently using a yeast process. According to a survey that the International Diabetes Federation conducted in 2002 on the access to and availability of insulin in its member countries, approximately 70% of the insulin that is currently sold in the world is recombinant, biosynthetic 'human' insulin. A majority of insulin used clinically today is produced this way, although clinical experience has provided conflicting evidence on whether these insulins are any less likely to produce an allergic reaction. Adverse reactions have been reported; these include loss of warning signs that patients may slip into a coma through hypoglycemia, convulsions, memory lapse and loss of concentration. However, the International Diabetes Federation's position statement from 2005 is very clear in stating that "there is NO overwhelming evidence to prefer one species of insulin over another" and "[modern, highly purified] animal insulins remain a perfectly acceptable alternative." Since January 2006, all insulins distributed in the US and some other countries are synthetic "human" insulins or their analogues. A special FDA importation process is required to obtain bovine or porcine derived insulin for use in the US, although there may be some remaining stocks of porcine insulin made by Lilly in 2005 or earlier, and porcine lente insulin is also sold and marketed under the brand name Vetsulin(SM) in the US for veterinary usage in the treatment of companion animals with diabetes.
== Medical use == Aminocaproic acid (Amicar) is FDA-approved for use in the treatment of acute bleeding due to elevated fibrinolytic activity. It also carries an orphan drug designation from the FDA for the prevention of recurrent hemorrhage in patients with traumatic hyphema. In clinical practice, aminocaproic acid is frequently used off-label for control of bleeding in patients with severe thrombocytopenia, control of oral bleeding in patients with congenital and acquired coagulation disorders, control of perioperative bleeding associated with cardiac surgery, prevention of excessive bleeding in patients on anticoagulation therapy undergoing invasive dental procedures, and reduction of the risk of catastrophic hemorrhage in patients with acute promyelocytic leukemia.
In chromatography substances are separated by partition between a stationary phase and a mobile phase. The analyte is dissolved in the mobile phase, and passes over the stationary phase. Separation occurs because of differing affinities of the analytes for the stationary phase. A distribution constant, Kd can be defined as
Sources: en.wikipedia.org
The port is accessible by road from the M20/A20 (leading to Folkestone) and the M2/A2 (to Canterbury), and by train from Dover Priory station with Southeastern services to London St Pancras via Folkestone Central, Ashford International, Ebbsfleet International, Stratford International as well as trains to London Victoria or London Charing Cross via Canterbury East and the Medway towns such as Gillingham, Chatham and Rochester or via Ashford International then either via Tonbridge and Sevenoaks or Maidstone East. There are trains to Deal and Ramsgate.
Modern food processing technology developed in the 19th and 20th centuries was developed in a large part to serve military needs. In 1809, Nicolas Appert invented a hermetic bottling technique that would preserve food for French troops which ultimately contributed to the development of tinning, and subsequently canning by Peter Durand in 1810. Although initially expensive and somewhat hazardous due to the lead used in cans, canned goods would later become a staple around the world. Pasteurization, discovered by Louis Pasteur in 1864, improved the quality and safety of preserved foods and introduced the wine, beer, and milk preservation. During the late nineteenth and early twentieth centuries, synthetic dyes began being used in food production to enhance or standardize the color of food products such as butter and processed goods. This reflected broad industrial efforts to control the appearance of consumer products.
=== Bolus shape === An insulin pump user can influence the profile of the rapid-acting insulin by shaping the bolus. Users can experiment with bolus shapes to determine what is best for any given food, which means that they can improve control of blood sugar by adapting the bolus shape to their needs. A standard bolus is an infusion of insulin pumped completely at the onset of the bolus. It's the most similar to an injection. By pumping with a "spike" shape, the expected action is the fastest possible bolus for that type of insulin. The standard bolus is most appropriate when eating high carb, low protein, low fat meals because it will return blood sugar to normal levels quickly. An extended bolus is a slow infusion of insulin spread out over time. By pumping with a "square wave" shape, the bolus avoids a high initial dose of insulin that may enter the blood and cause low blood sugar before digestion can facilitate sugar entering the blood. The extended bolus also extends the action of insulin well beyond that of the insulin alone. The extended bolus is appropriate when covering high fat high protein meals such as steak, which will be raising blood sugar for many hours past the onset of the bolus. The extended bolus is also useful for those with slow digestion (such as with gastroparesis or coeliac disease). A combination bolus/multiwave bolus is the combination of a standard bolus spike with an extended bolus square wave. This shape provides a large dose of insulin up front, and then also extends the tail of the insulin action.
In males, testosterone is synthesized primarily in Leydig cells. The number of Leydig cells in turn is regulated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In addition, the amount of testosterone produced by existing Leydig cells is under the control of LH, which regulates the expression of 17β-hydroxysteroid dehydrogenase. The amount of testosterone synthesized is regulated by the hypothalamic–pituitary–testicular axis (Figure 2). When testosterone levels are low, gonadotropin-releasing hormone (GnRH) is released by the hypothalamus, which in turn stimulates the pituitary gland to release FSH and LH. These latter two hormones stimulate the testis to synthesize testosterone. Finally, increasing levels of testosterone through a negative feedback loop act on the hypothalamus and pituitary to inhibit the release of GnRH and FSH/LH, respectively. Factors affecting testosterone levels may include:
Sources: en.wikipedia.org
=== DHIS2 === DHIS version 2 (from 2004) is a continuation of DHIS version 1 developed on open source Java technologies and available as an online web application. The first release, version 2.0, came in February 2008 after three years of development releases, and the most recent version is 43.0.1 (as of June 2026). DHIS2 is developed using open-source Java frameworks and tools, such as the Spring Framework, Hibernate, Struts2, Maven, and JUnit.
== Background == The project was first unveiled in September 2025 and dedicated on 5 November 2025 during Trump's second term. In chronological order, every United States president is displayed via a black and white photograph in a gold frame, except for former president Joe Biden. In the place of Biden's portrait, Trump installed a photograph of an autopen, a device used to mechanically replicate a signature. In December 2025, the administration added permanent bronze plaques beneath each portrait, many of which were reportedly written or dictated by Trump himself. The descriptions on the plaques vary significantly based on Trump's personal and political assessment of his predecessors:
== See also == Barbro Hjalmarsson Biomarker (medicine), a protein or other biomolecule measured in a blood test Blood film, a way to look at blood cells under a microscope Blood gas test Blood lead level Hematology – Study of blood and blood diseases Luminol, a visual test for blood left at crime scenes. Reference ranges for blood tests Schumm test – Test for blood mismatch Category:Blood tests List of medical tests
Genomic Technologies, Inc. was one of the few companies to develop a large scale oligonucleotide synthesizer that was, from the ground up, an oligonucleotide synthesizer. The initial platform called the VLSS for very large scale synthesizer utilized large Pharmacia liquid chromatograph columns as reactors and could synthesize up to 75 mmol of material. Many oligonucleotide synthesis factories designed and manufactured their own custom platforms and little is known due to the designs being proprietary. The VLSS design continued to be refined and is continued in the QMaster synthesizer which is a scaled down platform providing milligram to gram amounts of synthetic oligonucleotide. The current practices of synthesis of chemically modified oligonucleotides on large scale have been recently reviewed.
Bats possess a highly adapted respiratory system to cope with the demands of powered flight. They have relatively large lungs, and many species have proportionally larger alveolar surface areas and pulmonary capillary blood volumes than other mammals. During flight, the respiratory cycle has a one-to-one relationship with the wing-beat cycle. Their mammalian lungs prevent them from flying at high altitudes. Bats can also meet oxygen demands by exchanging gas through the patagium of the wing. When the bat has its wings spread, it allows for an increase in surface area to volume ratio, 85% of the surface area being the wing. The subcutaneous vessels in the membrane lie near the surface and allow for the diffusion of oxygen and carbon dioxide. The digestive system of bats varies depending on the species of bat and its diet. Digestion is relatively quick to meet the energy demands of flight. Insectivorous bats may have certain digestive enzymes to better process insects, such as chitinase to break down their chitin exoskeleton. Vampire bats, probably due to their diet of blood, are unique among vertebrates in that they do not have the enzyme maltase, which breaks down malt sugar, in their intestinal tract. Nectivorous and frugivorous bats have more maltase and sucrase enzymes than insectivores, to cope with the higher sugar contents of their diet. The adaptations of the kidneys of bats vary with their diets. Carnivorous and vampire bats consume large amounts of protein and can output concentrated urine; their kidneys have a thin cortex and long renal papillae.
Sources: en.wikipedia.org
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.
Enzymatic recycling assays measure total glutathione, while HPLC and LC-MS/MS can resolve GSH and GSSG separately. Derivatization or thiol-blocking reagents are sometimes used to stabilize and detect the compounds. Method choice depends on the sample type and required specificity.
Dry glutathione powder is typically stored at -20 °C in a desiccated container protected from light. Solutions should be prepared fresh, kept acidic or frozen, and avoid repeated freeze-thaw cycles. Stability should be confirmed for each specific laboratory condition.
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.