scholarly journals Kinetics of superoxide scavenging by dismutase enzymes and manganese mimics determined by electron spin resonance

1992 ◽  
Vol 281 (3) ◽  
pp. 795-802 ◽  
Author(s):  
B Gray ◽  
A J Carmichael
Keyword(s):  
Superoxide Dismutase ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Superoxide Anion ◽  
Spin Trap ◽  
Reaction System ◽  
Potassium Superoxide ◽  
Spin Resonance ◽  
Order Of Magnitude ◽  
Kinetics Of

This study presents an e.s.r. assay for superoxide dismutase (SOD). Enzymic reactions were studied in which Cu,Zn-SOD, Mn-SOD and Fe-SOD each competed with the spin trap 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) for superoxide anion (O2-) at pH 7.8 O2- from dissolved KO2 (potassium superoxide) in dimethyl sulphoxide was added directly to the enzyme solutions containing DMPO. The results show that, in this competition reaction system, the kinetics of the reactions between the enzymes and O2- follow a function y = f[(SOD]0.5). The rate constant, kSOD = 6.4 x 10(9) M-1. S-1, determined for Cu,Zn-SOD is approximately an order of magnitude larger than those for Mn-SOD and Fe-SOD. A comparative study of reported SOD mimics, including Mn2+, MnO2-desferrioxamine mesylate (Desferal) and MnO2-Desferal-ascorbate, was done. The results show that solutions of these complexes are approximately three orders of magnitude less active than Cu,Zn-SOD and approximately two orders of magnitude less active than Mn-SOD or Fe-SOD. The results also suggest that the reactivity toward O2- in solutions of these complexes originates from the Mn2+ present and not from the MnO2-Desferal complexes.

Purification of Superoxide Dismutase From Fungi and Characterization of the Reaction of the Enzyme with Catechols by Electron Spin Resonance Spectroscopy

1973 ◽  
Vol 51 (2) ◽  
pp. 158-171 ◽  
Author(s):  
Ursula Rapp ◽  
Wyman C. Adams ◽  
Richard W. Miller
Keyword(s):  
Superoxide Dismutase ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Superoxide Anion ◽  
Electron Spin Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Assay Procedure ◽  
Electrophoretic Behavior ◽  
Spin Resonance ◽  
Complex Relationships

Superoxide dismutase catalyzes the conversion of the single electron reduced species of molecular oxygen to hydrogen peroxide and oxygen. The widely distributed copper enzyme has been purified from two fungi. Identical chromatographic and electrophoretic behavior of the enzyme isolated from different sources indicates great similarity in the molecular properties of the enzyme from eucaryotic organisms. A photosensitized recording assay procedure for the enzyme was developed which elminates the use of a second enzyme system for generating the substrate, superoxide anion. Kinetic data indicate that the reaction between enzyme and superoxide anion shows a logarithmic dependence on concentration under the conditions of the method.The fungal enzyme contains 2 mol of zinc and 2 mol of copper per mole of holoenzyme. The reaction between the enzyme-bound copper and several catechol derivatives has been examined through the use of electron spin resonance spectroscopy. It was concluded from these studies that these compounds reduce a portion of the copper to the cuprous form and also may form a complex with enzyme copper. The substituted catechols are oxidized noncatalytically by the enzyme to the semiquinone forms in the presence of oxygen. Much higher concentrations of the semiquinones are formed in the presence of the enzyme than are possible with oxygen alone at pH 8. Catechols also react readily with superoxide anion. Because of the complex relationships between catechols, superoxide anion, and superoxide dismutase, it is difficult to assess the effect of catechols on the catalytic activity of the enzyme.

scholarly journals Estimation of the Postmortem Duration of Mouse Tissue by Electron Spin Resonance Spectroscopy

2011 ◽  
Vol 2011 ◽  
pp. 1-11
Author(s):  
Shinobu Ito ◽  
Tomohisa Mori ◽  
Hideko Kanazawa ◽  
Toshiko Sawaguchi
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Spin Trap ◽  
Detection Sensitivity ◽  
Mouse Tissue ◽  
Spin Adduct ◽  
Simple Method ◽  
Oxidation Stress ◽  
Spin Resonance

Electron spin resonance (ESR) method is a simple method for detecting various free radicals simultaneously and directly. However, ESR spin trap method is unsuited to analyze weak ESR signals in organs because of water-induced dielectric loss (WIDL). To minimize WIDL occurring in biotissues and to improve detection sensitivity to free radicals in tissues, ESR cuvette was modified and used with 5,5-dimethtyl-1-pyrroline N-oxide (DMPO). The tissue samples were mouse brain, hart, lung, liver, kidney, pancreas, muscle, skin, and whole blood, where various ESR spin adduct signals including DMPO-ascorbyl radical (AsA∗), DMPO-superoxide anion radical (OOH), and DMPO-hydrogen radical (H) signal were detected. Postmortem changes in DMPO-AsA∗and DMPO-OOH were observed in various tissues of mouse. The signal peak of spin adduct was monitored until the 205th day postmortem. DMPO-AsA∗in liver (y=113.8–40.7 log (day),R1=-0.779,R2=0.6,P<.001) was found to linearly decrease with the logarithm of postmortem duration days. Therefore, DMPO-AsA∗signal may be suitable for detecting an oxidation stress tracer from tissue in comparison with other spin adduct signal on ESR spin trap method.

scholarly journals Measurement of Serum Superoxide Dismutase Activity by Electron Spin Resonance

1988 ◽  
Vol 5 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Haruo MIYAGAWA ◽  
Toshikazu YOSHIKAWA ◽  
Toru TANIGAWA ◽  
Norimasa YOSHIDA ◽  
Shigeru SUGINO ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Superoxide Dismutase Activity ◽  
Spin Resonance

Radiation damage in polyethylene as studied by electron spin resonance

1961 ◽  
Vol 262 (1309) ◽  
pp. 207-218 ◽  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Alkyl Radical ◽  
Room Temperature ◽  
Chemical Properties ◽  
Resonance Method ◽  
Alkyl Radicals ◽  
Spin Resonance ◽  
Physical And Chemical ◽  
Kinetics Of

The electron spin resonance method was employed to study the nature, concentration and kinetics of the disappearance under varying conditions of radicals produced in polyethylene by fast electron irradiation at 77°K. The predominant radical species at 77°K is the alkyl radical —CH 2 —ĊH—CH 2 —. On being warmed to room temperature it disappears rapidly, revealing a more stable un­identified radical. The kinetics of the decay at room temperature of both radicals was observed. Their stabilities were found to vary in polyethylene samples of differing physical and chemical properties. G values for these radicals are given. Comparison was made with spectra obtained under similar conditions with two pure paraffins and a pure olefin to evaluate the effect of crystallinity branching, molecular weight and unsaturation. In the olefin there is evidence for a build-up of allyl radicals due to the encounter of an alkyl radical with main chain unsaturation. This supports the view that alkyl radicals are mobile, and cross-linking occurs when two such radicals meet.

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