LC-MS/MS comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2025-11-19. Where a claim depends on a specific study, the study is described rather than over-claimed.
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 a tripeptide composed of glutamate, cysteine, and glycine. It occurs in nearly all living cells, with highest concentrations in liver, kidney, and red blood cells, and exists in reduced (GSH) and oxidized disulfide (GSSG) forms. The cysteine thiol group enables reversible oxidation and reduction reactions. This property makes glutathione a central participant in cellular redox balance. The balance between these forms is often used as an indicator of oxidative stress.
Glutathione synthesis proceeds in two ATP-dependent steps catalyzed by glutamate-cysteine ligase and glutathione synthetase. The first step joins glutamate and cysteine to form gamma-glutamylcysteine and is generally rate-limiting. The second step adds glycine to complete the tripeptide. Cysteine availability, feedback inhibition by glutathione, and oxidative conditions influence flux through this pathway. The pathway is conserved across many organisms, and degradation by gamma-glutamyl transpeptidase and related peptidases recycles amino acids for new synthesis.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | -20 °C or below | For solid reagent and frozen aliquots; protect from moisture and light. |
| Common analytical method | HPLC with UV or fluorescence detection | Separates GSH and GSSG after derivatization or direct detection. |
| Alternative method | LC-MS/MS | Provides high specificity and can quantify multiple thiols. |
| Total glutathione assay | Enzymatic recycling | Uses glutathione reductase and a chromogen or fluorogen. |
| Key stability risk | Oxidation to GSSG | Air, light, and trace metals promote conversion. |
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.
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.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. Its glutamate-cysteine linkage uses the gamma-carboxyl group of glutamate, a feature that resists standard peptidases. The cysteine residue provides a thiol group, which gives the molecule its reducing character. In cells, glutathione is often the most abundant small-molecule thiol, with concentrations varying widely by tissue and compartment. It exists mainly in a reduced form called GSH, while oxidation produces a disulfide-linked dimer called GSSG.
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.
== Criticism == Criticism of cold fusion claims generally take one of two forms: either pointing out the theoretical implausibility that fusion reactions have occurred in electrolysis setups or criticizing the excess heat measurements as being spurious, erroneous, or due to poor methodology or controls. There are several reasons why known fusion reactions are an unlikely explanation for the excess heat and associated cold fusion claims.
== Chimera identification == Non-artificial chimerism has traditionally been considered to be rare due to the low amount of reported cases in medical literature. However, this may be due to the fact that humans might not often be aware of this condition to begin with. There are usually no signs or symptoms for chimerism other than a few physical symptoms such as hyper-pigmentation, hypo-pigmentation, Blaschko's lines, body asymmetry or heterochromia iridum (possessing two different colored eyes). However, these signs do not necessarily mean an individual is a chimera and should only be seen as possible symptoms. Again, forensic investigation or curiosity over an unexpected maternity/paternity DNA test result usually leads to the accidental discovery of this condition. By simply undergoing a DNA test, which usually consists of either a swift cheek swab or a blood test, the discovery of the once unknown second genome is made, therefore identifying that individual as a chimera.
ECU Health (formerly Vidant Health) is a not-for-profit, 1,447-bed hospital system that serves more than 1.4 million people in 29 Eastern North Carolina counties. The health system is made up of nine hospitals and more than 12,000 employees. ECU Health also includes wellness centers, home health and hospice services, a dedicated children's hospital, rehab facilities, pain management and wound healing centers and specialized cancer care. Their flagship hospital, ECU Health Medical Center, is a level I trauma center and serves as the teaching hospital for the Brody School of Medicine at East Carolina University in Greenville. Its smaller, community-based hospitals serve as patient feeders to the main hospital. The main hospital has shuttered services at these facilities only to reroute state licenses and permits back to the main hospital. ECU Health is the largest private employer in Eastern North Carolina. All nine ECU Health hospitals have achieved The Gold Seal of Approval for quality care by The Joint Commission, the leading accreditor of healthcare organizations in America. In 2002, the organization implemented a program in which diabetes educators regularly visit rural clinics to improve glycemic control in African-American patients. ECU Health changed their name from University Health Systems of Eastern Carolina in January 2012 to Vidant Health. On January 3, 2022, Vidant Health announced that they would be rebranding as ECU Health. In the announcement, they indicated that it would take several months for the branding to be noticeable to the public.
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== Causes == Despite extensive investigation, the cause of IPF remains unknown. The fibrosis in IPF has been linked to cigarette smoking, environmental factors (e.g. occupational exposure to gases, smoke, chemicals or dusts), other medical conditions including gastroesophageal reflux disease, or to genetic predisposition (familial IPF). Certain environmental factors and exposures have been shown to increase the risk of IPF. Cigarette smoking is the best recognized and most accepted risk factor, and increases the risk of IPF by about twofold. Other environmental and occupational exposures such as exposure to metal dust, wood dust, coal dust, silica, stone dust, biologic dusts coming from hay dust or mold spores or other agricultural products, and occupations related to farming/livestock have also been shown to increase the risk for IPF. There is some evidence that viral infections may be associated with idiopathic pulmonary fibrosis and other fibrotic lung diseases.
== Function == Nicotinamide adenine dinucleotide, is a coenzyme found in all cells. It is produced by nicotinamide-nucleotide adenylyltransferase, which combines adenosine triphosphate and nicotinamide mononucleotide, with inorganic pyrophosphate (PPi) produced as a byproduct:
One of the groups, the Camp of National Unity, combined many nationalists with Sanation supporters and was connected to the new strongman, Marshal Edward Rydz-Śmigły, whose faction of the Sanation ruling movement was increasingly nationalistic. In the late 1930s, the exile bloc Front Morges united several major Polish anti-Sanation figures, including Ignacy Paderewski, Władysław Sikorski, Wincenty Witos, Wojciech Korfanty and Józef Haller. It gained little influence inside Poland, but its spirit soon reappeared during World War II, within the Polish government-in-exile.
=== Solubility === Veratridine has a pKa of 9.54. It is slightly soluble in ether, soluble in ethanol and DMSO, and freely soluble in chloroform. Solubility in water is pH-dependent; the free base form is slightly soluble, but easily dissolves in 1 M HCl. Its nitrate salt is slightly soluble in water. Its sulfate salt is very hygroscopic.
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=== 30 May === At least 28 people were killed in RSF attacks on El-Obeid, Dibebad and Al Khuwayyi. Among the dead were six people killed in a drone attack on a hospital in El-Obeid. A World Food Programme (WFP) warehouse in El Fasher was damaged by shelling blamed on the RSF.
Frozen sectioning for intraoperative consultation Preparing tissue samples for flow cytometry, immunohistochemical (IHC) stains, genetic testing, microbiology culturing, and for various other laboratory evaluations Gross specimen photography Training pathology residents, PA fellows, and other pathology lab personnel (as needed) Fulfilling roles in managerial duties, instructional positions, and supervisory roles Research While many PAs are employed in hospitals, they may also gain employment in private pathology laboratories/groups, medical examiner's offices, morgues, government or reference laboratories, or universities, and may be self-employed and provide contract work.
Because of the greater stability of thioacetals, the equilibrium lies on the side of the acetal. In contradistinction to the O,O‑acetal case, it is not needed to remove water from the reaction mixture in order to shift the equilibrium. S,O-Acetals are hydrolyzed a factor of 10,000 times faster than the corresponding S,S-acetals. Their formation follows analogously from the thioalcohol. Also their cleavage proceeds under similar conditions and predominantly through mercury(II) compounds in wet acetonitrile. For aldehydes, a temporary protection of the carbonyl group the presence of ketones as hemiaminal ions is shown below. Here it is applied, that aldehydes are very much more activated carbonyls than ketones and that many addition reactions are reversible.
Sources: en.wikipedia.org
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.
Total glutathione typically refers to the combined amount of reduced glutathione and glutathione disulfide, expressed in glutathione equivalents. Assays that measure total glutathione do not distinguish GSH from GSSG unless a separation step is included. Researchers often pair a total assay with a specific GSSG measurement to estimate the redox ratio.
Glutathione reference standards are generally stored cold, dry, and protected from light. Weighed portions should be prepared promptly and used within validated stability windows. Purity and water content can affect the accuracy of calibration curves.
GSH is the reduced thiol form, while GSSG is the disulfide-linked oxidized dimer. The GSH:GSSG ratio is used as a redox indicator, though the ratio can vary with sample handling and cell type.