The short version of LC-MS/MS fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-01-05 and is reviewed periodically as new material appears.
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.
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.
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.
| 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. |
Samples for glutathione analysis require careful handling because the compound oxidizes readily and can be consumed by enzymes after collection. Blood is often treated with acid or thiol-blocking agents soon after draw, and plasma should be separated quickly from red blood cells. Tissues are usually snap-frozen or extracted immediately. Aqueous solutions of glutathione are less stable than dry powder and degrade faster at neutral or alkaline pH, in light, or with dissolved oxygen. Repeated freeze-thaw cycles also reduce reliability.
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.
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.
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.
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.
JDTic is a selective, long-acting ("inactivating") antagonist of the κ-opioid receptor (KOR). JDTic is a 4-phenylpiperidine derivative, distantly related structurally to analgesics such as pethidine and ketobemidone, and more closely to the MOR antagonist alvimopan. In addition, it is structurally distinct from other KOR antagonists such as norbinaltorphimine. JDTic has been used to create crystal structures of KOR [ PDB: 4DJH, 6VI4].
The clearance of a substance is the volume of plasma that contains the same amount of the substance as has been removed from the plasma per unit time. When referring to the function of the kidney, clearance is considered to be the amount of liquid filtered out of the blood that gets processed by the kidneys or the amount of blood cleaned per time because it has the units of a volumetric flow rate [ volume per unit time ]. However, it does not refer to a real value; "the kidney does not completely remove a substance from the total renal plasma flow." From a mass transfer perspective and physiologically, volumetric blood flow (to the dialysis machine and/or kidney) is only one of several factors that determine blood concentration and removal of a substance from the body. Other factors include the mass transfer coefficient, dialysate flow and dialysate recirculation flow for hemodialysis, and the glomerular filtration rate and the tubular reabsorption rate, for the kidney. A physiologic interpretation of clearance (at steady-state) is that clearance is a ratio of the mass generation and blood (or plasma) concentration. Its definition follows from the differential equation that describes exponential decay and is used to model kidney function and hemodialysis machine function:
=== International Classification of Diseases === The 2017 update to the American version of the ICD-10 includes binge eating disorder (BED) under F50.81. ICD-11 contain a dedicated entry (6B82), defining BED as frequent, recurrent episodes of binge eating occurring at least once a week or more over several months which are not regularly followed by inappropriate compensatory behaviors aimed at preventing weight gain. According to the World Health Organization's ICD-11 classification of BED, the severity of the disorder can be classified as mild (1–3 episodes/week), moderate (4–7 episodes/week), severe (8–13 episodes/week) and extreme (>14 episodes/week).
Sources: en.wikipedia.org
===== Methods ===== Methods of functionalizing the 4RepCT protein have been successful, but not in the way of reliably producing a stable protein functionalization in biologic environments that can also be tuned and modified. Genetic fusion of functional peptide sequences to silk genes and chemical conjugation of functional molecules onto amino acid side chains are the only two methods currently known to achieve a functionalized 4RepCT protein with tunable functionality. The first approach has the advantage that post-translational manipulation of the silk is minimized. Unfortunately, genetic manipulation is challenging due to the high GC (guanine-cytosine) content of the gene which leads to transcription errors. This method also limits the prevalence of functional binding sites to a single ligand-binding site per 25 kDa 4RepCT silk protein. Large adaptor proteins such as antibodies can be used to display more binding sites, but it isn't considered a feasible solution. This method has been shown to produce 4RepCT proteins that have a higher cell adhesion than natural spidroin proteins and have varied antimicrobial properties. The second method, chemical modification of the silk proteins should result in the covalent attachment of several copies of a wide range of organic and organometallic ligands using robust or sensitive linkers depending on the application. The challenge with this method is it is difficult to make the modification of the 4RepCT protein site-specific.
=== Subcellular localization === C3orf62 is predicted to be localized in the nucleus. The k-nearest neighbors algorithm predicts C3orf62 to be classified as follows: k=9/23; 69.6% nuclear, 13.0% mitochondrial, 13.0% cytoskeletal, 4.3% cytoplasmic.
== The Protein == The 25-kDa core protein (excluding the heavy glycosylation) of rodent Thy-1 is 111 or 112 amino acids in length, and is N-glycosylated at three sites (In contrast to only two glycosylation sites for human Thy-1). The 162aa (murine, 161 for human) Thy1 precursor has 19 amino acid (aa 1–19) signal sequence and 31 amino acid (aa 132–162) C-terminal transmembrane domain that is present in pro form but removed when transferring the 112 amino acid (aa 20–131) mature peptide to GPI anchor which would attach through the aa 131. Some of the common monoclonal antibodies used to detect this protein are clones OX7, 5E10, K117 and L127. There have been some reports of Thy1 monoclonal antibodies cross reacting with some cytoskeletal elements: anti Thy-1.2 with actin in marsupial, murine, and human cells and anti Thy-1.1 with vimentin, and were suggested to be due to sequence homology by studies done more than 20 years back. Thy-1, like many other GPI anchored proteins can be shed by special types of Phospholipase C e.g. PI-PLC (phosphatidyl-Inositol Phospholipase C, or PLC β). it can also be involved in cell to cell transfer of GPI anchored proteins like CD55 and CD59.
NpOF3 and NpOF4 can be produced by reacting neptunium oxides with anhydrous hydrogen fluoride at various temperatures. Neptunium also forms a wide variety of fluoride compounds with various elements. Some of these that have been characterized include CsNpF6, Rb2NpF7, Na3NpF8, and K3NpO2F5. Two neptunium chlorides, NpCl3 and NpCl4, have been characterized. Although several attempts to obtain NpCl5 have been made, they have not been successful. NpCl3 is produced by reducing neptunium dioxide with hydrogen and carbon tetrachloride (CCl4) and NpCl4 by reacting a neptunium oxide with CCl4 at around 500 °C. Other neptunium chloride compounds have also been reported, including NpOCl2, Cs2NpCl6, Cs3NpO2Cl4, and Cs2NaNpCl6. Neptunium bromides NpBr3 and NpBr4 have also been produced; the latter by reacting aluminium bromide with NpO2 at 350 °C and the former in an almost identical procedure but with zinc present. The neptunium iodide NpI3 has also been prepared by the same method as NpBr3.
Sources: en.wikipedia.org
Singapore has a tropical rainforest climate (Köppen: Af) with no distinctive seasons, uniform temperature and pressure, high humidity, and abundant rainfall. Temperatures usually range from 23 to 32 °C (73 to 90 °F). While temperature does not vary greatly throughout the year, there is a wetter monsoon season from November to February. From July to October, there is often haze caused by bush fires in neighbouring Indonesia, usually from the island of Sumatra. Singapore follows the GMT+8 time zone, one hour ahead of the typical zone for its geographical location. This causes the sun to rise and set particularly late during February, where the sun rises at 7:15 am and sets around 7:20 pm. During July, the sun sets at around 7:15 pm. The earliest the sun rises and sets is in late October and early November when the sun rises at 6:46 am and sets at 6:50 pm. Singapore recognises that climate change and rising sea levels in the decades ahead will have major implications for its low-lying coastline. It estimates that the nation will need to spend $100 billion over the course of the next century to address the issue. In its 2020 budget, the government set aside an initial $5 billion towards a Coastline and Flood Protection Fund. Singapore is the first country in Southeast Asia to levy a carbon tax on its largest carbon-emitting corporations producing more than 25,000 tons of carbon dioxide per year, at $5 per ton.
No visible clubbing – Fluctuation (increased ballotability) and softening of the nail bed only. No visible changes in nails. Mild clubbing – Loss of the normal <165° angle (Lovibond angle) between the nailbed and the fold (cuticula). Schamroth's window (see image) is obliterated. Clubbing is not obvious at a glance. Moderate clubbing – Increased convexity of the nail fold. Clubbing is apparent at a glance. Gross clubbing – Thickening of the whole distal (end part of the) finger (resembling a drumstick) Hypertrophic osteoarthropathy – Shiny aspect and striation of the nail and skin Schamroth's sign or Schamroth's window test (originally demonstrated by South African cardiologist Leo Schamroth on himself) is a popular test for clubbing. When the distal phalanges (bones nearest the fingertips) of corresponding fingers of opposite hands are directly opposed (place fingernails of the same finger on opposite hands against each other, nail to nail), a small diamond-shaped "window" is normally apparent between the nailbeds. If this window is obliterated, the test is positive, and clubbing is present.
To describe and organize the structures of MOFs, a system of nomenclature has been developed. Subunits of a MOF, called secondary building units (SBUs), can be described by topologies common to several structures. Each topology, also called a net, is assigned a symbol, consisting of three lower-case letters in bold. MOF-5, for example, has a pcu net. Attached to the SBUs are bridging ligands. For MOFs, typical bridging ligands are di- and tricarboxylic acids. These ligands typically have rigid backbones. Examples are benzene-1,4-dicarboxylic acid (H2bdc or terephthalic acid), biphenyl-4,4′-dicarboxylic acid (H2bpdc), and the tricarboxylic acid trimesic acid. A fundamental aspect in the development of MOFs is that their crystal structures can be determined by X-ray crystallographic techniques as often, many MOFs have good crystallinity allowing their 3D structures to be determined precisely. This has allowed to study reactions taking place within the MOF's channels, revealing the structures of reaction intermediates.
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.
Acidification lowers pH and helps prevent oxidation of the thiol group during extraction and storage. It can also precipitate proteins and stabilize the reduced form before analysis.