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Oxidative stress occurs when the ability of an organism to effectively remove free radicals (eg reactive oxygen species) is insufficient to reduce the generation of reactive intermediates or is unable to repair the resulting cellular damage.
Free radicals are so reactive and short-lived that direct measurement is usually not possible. However, hundreds of biomolecules are known to be derived from the interaction of free radicals with biomolecules. Assays for some of these oxidative stress biomarkers, as well as assays for several of the body’s antioxidant defence mechanisms, have been widely used. Although there are numerous tools on the market, a small number of oxidised lipids, as well as by products of DNA and protein oxidation, have withstood the test of time. Oxford Biomedical Research provides researchers with straightforward, reliable assays for oxidative stress biomarkers and for the measurement of the antioxidant capacity of biological fluids. |
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Products for Oxidative Stress Measurement
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GSH/GSSG Assays |
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Isoprostane Assays |
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TBARS Assays |
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Assay Prices |
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Literature and Technical Requests |
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Request Technical Literature |
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Oxford Biomedical Research Specific Products/Applications |
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Oxford Biomedical Research Products and Applications |
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Vascular Biology Feature |
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Assay Protocols
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GSH/GSSG Assay (Microplate) |
497KB |
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GSH/GSSG Assay (Cuvette) |
494KB |
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Urinary Isoprostane EIA Assay |
325KB |
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Isoprostane EIA Assay |
193KB |
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TBARS Assay (Colorimetric, microplate) |
1.0MB |
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TBARS Assay (Colorimetric/Fluorometric, cuvette) |
412KB |
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Antioxidant Measurement
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Total Antioxidant Power Assay
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 Improved Total Antioxidant Power Assay provides a broad dynamic range and is suitable for an expanded range of sample types. This assay provides accurate determination of the total antioxidant activity in a sample that results from the combined activities of the constituents, including vitamins, proteins, glutathione etc of the sample.
The assay works with both hydrophobic and hydrophilic compounds and can be used on many sample types including serum, tissue culture supernatant (TCS), foods etc. |
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GSH/GSSG Assays |
Reduced glutathione (GSH) is a tripeptide (γ-glutamylcysteinylglycine) that contains a free thiol group. GSH is a major tissue antioxidant that provides reducing equivalents for the glutathione peroxidase (GPx) catalysed reduction of lipid hydroperoxides to their corresponding alcohols and hydrogen peroxide to water.
When cells are exposed to increased levels of oxidative stress, GSSG will accumulate and the ratio of GSH to GSSG will decrease. Therefore, the determination of the GSH/GSSG ratio and the quantification of GSSG are useful indicators of oxidative stress levels in cells and tissues.
Assay Principle
Scavenging of Free Thiols:This assay employs a pyridine derivative as a thiol-scavenging reagent thereby overcoming the shortfalls of both prior methods. At the concentration employed in the assay, this derivative reacts quickly with GSH but does not interfere with the glutathione reductase (GR) activity. Reaction of the scavanger with a thiol forms a pyridinium salt.
Thiol Quantification: The quantitative determination of the total amount of glutathione (GSH + GSSG) employs the enzymatic method. Briefly, the reaction of GSH with Ellman’s reagent (5,5’-dithiobis-2-nitrobenzoic acid (DTNB)) gives rise to a product that can be quantified spectrophotometrically at 412 nm. This reaction is used to measure the reduction of GSSG to GSH. The rate of the reaction is proportional to the GSH and GSSG concentration. |
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Isoprostane Measurement
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Isoprostane Assays
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There is increasing evidence that isoprostanes play a causative role in artherogenesis and are a novel class of prostaglandin-like compounds which are produced following the peroxidation of lipoproteins. In normal humans, levels of the isoprostane 15-F2t-Isoprostane α (formerly 8-epi-Prostaglandin F2) range from 5-50 pg/mL plasma and 500 to 3000 pg/g urinary creatinine, respectively. The in vivo concentration of F2- isoprostanes increases dramatically in animal models of lipid peroxidation. Measurement of isoprostane concentrations is likely to have significant diagnostic potential for assessment of oxidative stress and several disorders such as atherosclerosis, rheumatoid arthritis, and carcinogenesis. Urine and tissue culture supernatants can usually be assayed directly by diluting them with the EIA buffer using Urinary Isoprostane EIA kit (EA85). Alternatively, 15-F2t-Isoprostane α can be extracted from plasma using Sep-Pak columns following the protocol provided with the kit. |
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Oxidised Lipid Measurment |
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TBARS Assays |
The TBARS (Thiobarbituric Acid Reactive substances) assay was developed for the measurement of MDA (malondialdehyde) production via lipid peroxidation and is a well established and widely used method for assessment of oxidative damage. However, as typically performed, the traditional method for TBARS analysis is often criticised for lack of specificity and sensitivity. Indeed, currently available TBARS assays require boiling the sample with strong acid which also generates interfering chromophores.
Oxford Biomedical Research has recently developed a room temperature TBARS method that eliminates the requirement for a high concentration of a strong acid and cuts reaction time in half. By running the assay at room temperature, low levels of interfering substances are generated. This results in more accurate, precise and reliable TBARS measurements. |
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Products and Applications 
