Product Manual
OxiSelect™ Superoxide Dismutase Activity Assay
Catalog Number
STA-340  100 assays
FOR RESEARCH USE ONLY
Not for use in diagnostic procedures
Introduction
Reactive oxygen species (ROS), such as superoxide (O2-) and hydrogen peroxide (H2O2), are constantl
y produced during metabolic processes in all living species.  Under normal physiological conditions, cellular ROS generation is counterbalanced by the action of antioxidant enzymes and other redox molecules.  However, excessive ROS accumulation will lead to cellular injury, such as damage to DNA, protein, and lipid membrane.  Because of their potential harmful effects, excessive ROS must be promptly eliminated from the cells by a variety of antioxidant defense mechanisms.  Superoxide dismutase (SOD), which catalyzes the dismutation of the superoxide anion into hydrogen peroxide and molecular oxygen, is one of the most important antioxidative enzymes.  SOD enzymes are classified into three groups: cytosolic Cu/Zn-SOD, mitochondrial Mn-SOD, and extracellular Ec-SOD.
Our OxiSelect™ Superoxide Dismutase Activity Assay uses a xanthine/xanthine oxidase (XOD) system to generate superoxide anions. The included chromagen produces a water-soluble formazan dye upon reduction by superoxide anions.  The activity of SOD is determined as the inhibition of chromagen reduction (See Figure 1).
The OxiSelect™ Superoxide Dismutase Activity Assay is a fast and reliable kit for the measurement of SOD activity from cell lysate, plasma, serum, tissue homogenates.  Each kit provides sufficient reagents to perform up to 100 assays, including blanks, SOD standards and unknown protein samples.
Assay Principle
Superoxide anions (O2-) are generated by a Xanthine/Xanthine Oxidase (XOD) system, and then detected with a Chromagen Solution.  However, in the presence of SOD, these superoxide anion concentrations are reduced, yielding less colorimetric signal.
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5.STA-332: OxiSelect™ MDA ELISA Kit
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7.STA-341: OxiSelect™ Catalase Activity Assay Kit
8.STA-342: OxiSelect™ Intracellular ROS Assay Kit (Green Fluorescence)
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Kit Components
1.SOD Standard (Part No. 234001):  One 100 µL vial provided at 5 Units/µL.  Unit Definition: One
unit will inhibit the rate of reduction of cytochrome c by 50% in a coupled system, using xanthine and xanthine oxidase, at pH 7.8 at 25°C in a 3.0 ml reaction volume.
reactive oxygen species (ros)2.Xanthine Solution (Part No. 234002):  One 550 µL vial.
3.Xanthine Oxidase Solution, 150X (Part No. 234003):  One 50 µL vial.
4.Chromagen Solution (Part No. 234004): One 550 µL amber vial.
5.SOD Assay Buffer, 10X (Part No. 234005): Two 1.5 mL vials.
Materials Not Supplied
1.96-well microtiter plate
2.37ºC incubator or water bath
3.10 µL to 1000 µL adjustable single channel micropipettes with disposable tips
4.50 µL to 300 µL adjustable multichannel micropipette with disposable tips
5.Multichannel micropipette reservoir
6.Microplate reader capable of reading at 490 nm
Storage
Store kit components at -20ºC until their expiration dates.  Avoid multiple freeze/thaws by aliquoting.  Chromagen Solution is light sensitive and should be maintained in amber tubes.
Preparation of Reagents
•1X SOD Assay Buffer:  Dilute one vial of 10X SOD Assay Buffer to 1X with deionized water.  Mix to homogeneity.  Keep the second vial of 10X SOD Assay Buffer undiluted.
•1X Xanthine Oxidase Solution:  Just prior to use, dilute the 150X Xanthine Oxidase Solution to 1X with 1X SOD Assay Buffer.  Mix to homogeneity.
Special Precautions
Avoid the use of reducing agents, such as DTT, in the assay due to interference with the Chromagen Solution.
Preparation of Samples
•Suspension Cells: Centrifuge 3-6 x 106 cells at 700 x g for 2 minutes and discard supernatant.  Wash cell pellet once with ice-cold PBS, centrifuge, and discard the supernatant.  Resuspend cell pellet in
0.5 mL of cold 1X Lysis Buffer (10 mM Tris, pH 7.5, 150 mM NaCl, 0.1 mM EDTA).  Lyse cells
with sonication or homogenation.  Centrifuge at 12000 x g for 10 minutes and collect the cell lysate supernatant.
•Adherent Cells: Wash 1-5 x 106 cells once with 10 mL ice-cold PBS per 100 mm dish.  Harvest cells with a cell with a cell scraper in 1 mL of cold 1X Lysis Buffer (10 mM Tris, pH 7.5, 150 mM NaCl, 0.1 mM EDTA).  Lyse cells with sonication or homogenation.  Centrifuge at 12000 x g for 10 minutes and collect the cell lysate supernatant.
•Tissue Lysates: Homogenize tissue sample in 5-10 mL of cold 1X Lysis Buffer (10 mM Tris, pH
7.5, 150 mM NaCl, 0.1 mM EDTA) per gram tissue.  Lyse cells with sonication or homogenation.
Centrifuge at 12000 x g for 10 minutes and collect the tissue lysate supernatant.
•Plasma:  Collect blood with an anticoagulant such as heparin, citrate or EDTA and mix by inversion.  Centrifuge the blood at 1000 x g at 4°C for 10 minutes.  Collect plasma supernatant without disturbing the white buffy layer.  Sample should be tested immediately or frozen at -80°C for storage.
•Serum:  Collect blood in a tube with no anticoagulant.  Allow the blood to clot at room temperature for 30 minutes.  Centrifuge at 2500 x g for 20 minutes.  Remove the yellow serum supernatant
without disturbing the white buffy layer.  Samples should be tested immediately or frozen at -80°C for storage.
Assay Protocol
1.Prepare samples including a blank in a 96-well microtiter plate according to the below table.  Allow
pre-incubation time if inhibitor is used.
2.Finally, add 10 µL of pre-diluted 1X Xanthine Oxidase Solution (see Preparation of Reagents) to
each well.  Mix well and incubate for 1 hour at 37ºC.
3.Read absorbance at 490 nm on a microplate reader.
Preparation of SOD Standards (Optional)
1.Thaw SOD Standard at 4ºC.
2.Freshly prepare a dilution series (1:4 is suggested) of SOD Standard in the concentration range of
5 Units/µL – 1.2 mU/µL by diluting the SOD Standard in 1X Assay Buffer (see Preparation of
Reagents).
3.Transfer 10 µL of each dilution to a 96-well microtiter plate, including a 1X Assay Buffer blank.
4.Prepare the following master mixture, adjusting for the required number of wells.
5.Transfer 80 µL of the above master mixture to each well.
6. Finally, add 10 µL of pre-diluted 1X Xanthine Oxidase Solution (see Preparation of Reagents) to each well.  Mix well and incubate for 1 hour at 37ºC.
7. Read absorbance at 490 nm on a microplate reader.
Example of Results
The following figures demonstrate typical OxiSelect™ SOD Activity Assay results.  One should use the data below for reference only.  This data should not be used to interpret actual results.  SOD Activity (inhibition %) = (OD blank -OD sample )/( OD blank ) x 100
Figure 1: SOD Activity Assay Standard Curve. Left : SOD activity as a function of optical density (OD). Right : SOD activity as a function of inhibition percentage.
References
1. Lepock, J. R., Arnold, L. D., Torrie, B. H., Andrews, B., and Kruuv, J. (1985) Arch. Biochem. Biophys. 241, 243–251.
2. Lepock, J. R., Frey, H. E., and Hallewell, R. A. (1990) J. Biol. Chem. 265, 21612–21618.
3. Valentine, J. S., and Hart, P. J. (2003) Proc. Natl. Acad. Sci. U. S. A. 100, 3617-3622.
4. Zelko, I. N., Mariani, T. J., and Folz, R. J. (2002) Free Radic. Biol. Med. 33, 337-349.
Recent Product Citations
1. Paneni, F. et al. (2013). Deletion of the Activated Protein-1 Transcription Factor JunD Induces Oxidative Stress and Accelerates Age-Related Endothelial Dysfunction. Circulation . 127:1229-1240.
2. Zhang, Z. et al. (2012). TRPM2 Ca2+ Channel Regulates Energy Balance and Glucose Metabolism. Am J Physiol Endocrinol Metab . 302:E807-E816.

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