Superoxide anion radical generation in the NaOH/H₂O₂/Fe(III) system: a spin trapping ESR study

Abstract

Formation of free radical intermediates in a NaOH/H(2)O(2)/Fe(III) system has been studied by ESR spectroscopy in the presence of the spin trap 5,5-dimethy-1-pyrroline N-oxide (DMPO). DMPO/O(2(*) ) (-) and DMPO/(*)OH signals were simultaneously detected in this system, but only the DMPO/(*)OH signal could be observed in the absence of Fe(III). Effects of pH values and Fe(III) concentrations on the ESR signal intensities were investigated in detail. Formation of DMPO/O(2(*) ) (-) adduct was inhibited by the addition of superoxide dismutase (SOD), catalase or nitro blue tetrazolium (NBT), and by chelating the Fe(III) with some chelators, including ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and desferrioxamine (DFO). Deoxygenation from the NaOH/H(2)O(2)/Fe(III) mixture had a slight effect on the formation of DMPO/O(2(*) ) (-). DMPO/O(2(*) ) (-) signal was also detected from the NaOH/H(2)O(2)/Fe(II) mixture, but it can be totally suppressed under anaerobic conditions. Considering the hydrolysis of Fe(III) into polymerization iron species with oxide phases in the alkaline medium, Fe(2)O(3) was directly suspended into a mixture of NaOH/H(2)O(2) for comparison. Fortunately, the presence of Fe(2)O(3) suspension was found to be of benefit to the production of DMPO/O(2(*) ) (-). Influence of aging time of hydrolytic iron species on the superoxide anion radical generation was also studied. These results suggest that the generation of O(2(*) ) (-) from the NaOH/H(2)O(2)/Fe(III) system was probably caused by the heterogeneous surface catalysis initiated by hydrolytic iron species.

Role of Operon aaoSo-mutT in Antioxidant Defense in Streptococcus oligofermentans

“…Considering that the accumulation of superoxide in cells is concomitant with abundant H 2 O 2 generated by lactate oxidase and pyruvate oxidase, and either superoxide anion or H 2 O 2 can cause the release of iron from proteins containing [4Fe–4S] 2+ clusters, the Fenton reaction can cause an elevation in cellular hydroxyl radicals [20]. Therefore, hydroxyl radicals were assessed in S. oligofermentans strains using electron spin resonance (ESR) with 5,5-dimethyl-1-pyrroline- N -oxide (DMPO) spin trap [21], [22]. ESR spectroscopy is the most efficient and non-destructive technique for detecting chemical species that have unpaired electrons, such as the superoxide anion radical and hydroxyl radical.…”

“…ESR spectroscopy is the most efficient and non-destructive technique for detecting chemical species that have unpaired electrons, such as the superoxide anion radical and hydroxyl radical. As a spin trap, DMPO has been frequently used to detect oxygen-centered radicals [22]. As shown in Fig.…”

“…Cellular ROS levels in S. oligofermentans were measured using a spin trapping agent combined with ESR spectroscopy (Bruker ESP 300, Germany) [21], [22]. 5,5-Dimethyl-l-pyrroline N -oxide (DMPO, TCI, Japan) was purified by stirring a solution (0.25 M) of the spin trap in deionized water with a little activated charcoal for 1 hour.…”

Degradation of trichloroethylene in aqueous solution by persulfate activated with citric acid chelated ferrous ion

“…Meanwhile, the degradation efficiency of AN was decreased from 37.5% to 17.9% within 12 h in PS/Fe(II)/CA system with the addition of 1 M TBA, meaning that CA chelated Fe(II) can activate PS to generate Å SO 4 À as well in the reaction. O 2 ÀÅ was a reductant and weak nucleophile that is detected in CHP system [44] and in activated PS system [18]. Owing to its ready degradation by O 2 ÀÅ (k = 1.6 Â 10 10 M À1 s À1 ), but not oxidation by Å OH (k ÅOH < 6 Â 10 6 M À1 s À1 ) [11], CT was used as a reductant probe to investigate the activity of O 2 ÀÅ in PS/Fe(II)/CA system.…”

DNA Backbone Sulfur-Modification Expands Microbial Growth Range under Multiple Stresses by its anti-oxidation function

“…TDH is a representative of a family of mononuclear enzymes that includes epimerases, dehydrogenases, deformylases and deaminases, which are highly sensitive to H 2 O 2 . As little as 0.5 μM H 2 O 2 can inactivate these enzymes, causing the release of Fe 3+ via the Fenton reaction between H 2 O 2 and iron 26 . After treating Hpx − /Dnd + and Hpx − / dnd mutant and MG1655 cells with 1 mM H 2 O 2 for 15 minutes, the total proteins were extracted, and TDH activities were assayed anaerobically.…”