A practical reference on LC-MS/MS: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-08-16. 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.
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.
| 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. |
Gearbox Software, L.L.C. is an American video game development company based in Frisco, Texas. It was established as a limited liability company in February 1999 by five developers formerly of Rebel Boat Rocker. Randy Pitchford, one of the founders, serves as president and chief executive officer. Gearbox initially created expansions for the Valve game Half-Life, then ported that game and others to console platforms. In 2005, Gearbox launched its first independent set of games, Brothers in Arms, on console and mobile devices. It became its flagship franchise and spun off a comic book series, television documentary, books, and action figures. Their second original game series, Borderlands, commenced in 2009, and by 2015 had sold over 26 million copies. The company also owns the intellectual property of Duke Nukem and Homeworld. Gearbox expanded into publishing with the creation of Gearbox Publishing in 2015. A parent company, The Gearbox Entertainment Company, was established for Gearbox Software and Gearbox Publishing in 2019. Gearbox Entertainment was acquired by the Embracer Group in April 2021, becoming its seventh major label. A third division, Gearbox Studios, focusing on television and film productions, was established in October 2021. Due to major restructuring following a failed investment, Embracer announced plans to divest Gearbox to Take-Two Interactive, who had previously published several of Gearbox's games under its 2K label, in March 2024. Take-Two Interactive closed the Gearbox Software acquisition on June 12, 2024.
=== Drug delivery platforms === In therapeutics, synthetic biology has achieved significant advancements in altering and simplifying the therapeutics scope in a relatively short period of time. In fact, new therapeutic platforms, from the discovery of disease mechanisms and drug targets to the manufacture and transport of small molecules, are made possible by the logical and model-guided design construction of biological components. Synthetic biology devices have been designed to act as therapies in therapeutic treatment. It is possible to control complete created viruses and organisms to target particular pathogens and diseased pathways. Thus, in two independent studies 91,92, researchers utilised genetically modified bacteriophages to fight antibiotic-resistant bacteria by giving them genetic features that specifically target and hinder bacterial defences against antibiotic activity. In the therapy of cancer, since conventional medicines frequently indiscriminately target tumours and normal tissues, artificially created viruses and organisms that can identify and connect their therapeutic action to pathological signals may be helpful. For example, p53 pathway activity in human cells was put into adenoviruses to control how they replicated.
In December 2018, CIJA chief Stephen Rapp who formerly served as the US Ambassador for Global Criminal Justice, stated that war-crimes committed by the Syrian regime constituted a "solid kind of evidence that we haven't really had since Nuremberg, when the Nazis were prosecuted." The proofs of documented crimes included a vast array of sources, ranging from 2 million video footages to the documents seized from the Baathist regional committees and command crisis centres. Rapp asserted that despite Russian objections in the UN Security Council, the evidences are sufficient for an international arrest warrant.
Sources: en.wikipedia.org
Many drug interactions are due to alterations in drug metabolism. Further, human drug-metabolizing enzymes are typically activated through the engagement of nuclear receptors. One notable system involved in metabolic drug interactions is the enzyme system comprising the cytochrome P450 oxidases.
== Prognosis == Without treatment, the risk of an ischemic stroke in the three months after a TIA is about 20% with the greatest risk occurring within two days of the TIA. Other sources cite that 10% of TIAs will develop into a stroke within 90 days, half of which will occur in the first two days following the TIA. Treatment and preventative measures after a TIA (for example treating elevated blood pressure) can reduce the subsequent risk of an ischemic stroke by about 80%. The risk of a stroke occurring after a TIA can be predicted using the ABCD² score. One limitation of the ABCD² score is that it does not reliably predict the level of carotid artery stenosis, which is a major cause of stroke in TIA patients. The patient's age is the most reliable risk factor in predicting any level of carotid stenosis in transient ischemic attack. The ABCD2 score is no longer recommended for triage (to decide between outpatient management versus hospital admission) of those with a suspected TIA due to these limitations.
Many macromolecular machines are found within cells, often in the form of multi-protein complexes. Examples of biological machines include motor proteins such as myosin, which is responsible for muscle contraction, kinesin, which moves cargo inside cells away from the nucleus along microtubules, and dynein, which moves cargo inside cells towards the nucleus and produces the axonemal beating of motile cilia and flagella. "[I]n effect, the [motile cilium] is a nanomachine composed of perhaps over 600 proteins in molecular complexes, many of which also function independently as nanomachines ... Flexible linkers allow the mobile protein domains connected by them to recruit their binding partners and induce long-range allostery via protein domain dynamics." Other biological machines are responsible for energy production, for example ATP synthase which harnesses energy from proton gradients across membranes to drive a turbine-like motion used to synthesise ATP, the energy currency of a cell. Still other machines are responsible for gene expression, including DNA polymerases for replicating DNA, RNA polymerases for producing mRNA, the spliceosome for removing introns, and the ribosome for synthesising proteins. These machines and their nanoscale dynamics are far more complex than any molecular machines that have yet been artificially constructed. Biological machines have potential applications in nanomedicine. For example, they could be used to identify and destroy cancer cells.
Three people are injured, with two hospitalised, after a gas explosion at a house in Ilford, north-east London. 11 December Urfan Sharif and Beinash Batool, the father and stepmother of 10-year-old Sara Sharif, are found guilty of her murder in August 2023. Avanti West Coast's train managers have voted to take three days of strike action over the festive period, on 22, 23 and 29 December, in an ongoing dispute about the company's "rest day working arrangements". The strikes are subsequently called off while a new offer is considered. Health Secretary Wes Streeting announces that the ban on giving puberty blockers to under-18s questioning their gender will be made permanent. The Scottish Government subsequently announces it will follow the UK by introducing a permanent ban in Scotland. It is reported that Elon Musk's Tesla car company pushed the newly elected Government of Keir Starmer to make petrol car drivers "pay more" in the days after the general election. 12 December HMS Triumph, the Royal Navy's last Trafalgar-class attack submarine, completes its final voyage before being decommissioned. 31-year-old Levi Fishlock is sentenced to nine years in prison for his part in the August riots, during which he set fire to a hotel housing asylum seekers in Rotherham. His sentence is the joint-longest of any handed down so far in relation to the disorder. 609 migrants cross the Channel in nine dinghies, the most ever on a December day since records began in 2018. This brings the total number of people crossing this year to 34,582, almost 20% more than 2023.
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 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.