scholarly journals Catalysis of Metal-Wool Complexes for Hydroxyl Radical Formation from Hydrogen Peroxide and Reaction of Wool Proteins with Hydroxyl Radicals.

1993 ◽  
Vol 49 (9) ◽  
pp. 474-481
Author(s):  
Tomoko Takahata ◽  
Kazuhiko Fukatsu
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Radical Formation ◽  
Wool Proteins

scholarly journals Superoxide dismutase enhances the formation of hydroxyl radicals in the reaction of 3-hydroxyanthranilic acid with molecular oxygen

1988 ◽  
Vol 251 (3) ◽  
pp. 893-899 ◽  
Author(s):  
H Iwahashi ◽  
T Ishii ◽  
R Sugata ◽  
R Kido
Keyword(s):  
Hydrogen Peroxide ◽  
Superoxide Dismutase ◽  
Hydroxyl Radical ◽  
Molecular Oxygen ◽  
Hydroxyl Radicals ◽  
Fenton Reaction ◽  
Potassium Phosphate ◽  
Radical Formation ◽  
Superoxide Anions ◽  
Hydroxyanthranilic Acid

Superoxide dismutase (SOD) enhanced the formation of hydroxyl radicals, which were detected by using the e.s.r. spin-trapping technique, in a reaction mixture containing 3-hydroxyanthranilic acid (or p-aminophenol), Fe3+ ions, EDTA and potassium phosphate buffer, pH 7.4. The hydroxyl-radical formation enhanced by SOD was inhibited by catalase and desferrioxamine, and stimulated by EDTA and diethylenetriaminepenta-acetic acid, suggesting that both hydrogen peroxide and iron ions participate in the reaction. The hydroxyl-radical formation enhanced by SOD may be considered to proceed via the following steps. First, 3-hydroxyanthranilic acid is spontaneously auto-oxidized in a process that requires molecular oxygen and yields superoxide anions and anthranilyl radicals. This reaction seems to be reversible. Secondly, the superoxide anions formed in the first step are dismuted by SOD to generate hydrogen peroxide and molecular oxygen, and hence the equilibrium in the first step is displaced in favour of the formation of superoxide anions. Thirdly, hydroxyl radicals are generated from hydrogen peroxide through the Fenton reaction. In this Fenton reaction Fe2+ ions are available since Fe3+ ions are readily reduced by 3-hydroxyanthranilic acid. The superoxide anions do not seem to participate in the reduction of Fe3+ ions, since superoxide anions are rapidly dismuted by SOD present in the reaction mixture.

scholarly journals Catalase Expression Is Modulated by Vancomycin and Ciprofloxacin and Influences the Formation of Free Radicals in Staphylococcus aureus Cultures

2015 ◽  
Vol 81 (18) ◽  
pp. 6393-6398 ◽  
Author(s):  
Ying Wang ◽  
Anni B. Hougaard ◽  
Wilhelm Paulander ◽  
Leif H. Skibsted ◽  
Hanne Ingmer ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Staphylococcus Aureus ◽  
Free Radicals ◽  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Bacterial Species ◽  
Iron Chelation ◽  
Radical Formation ◽  
Bacterial Cells ◽  
Content Type

ABSTRACTDetection of free radicals in biological systems is challenging due to their short half-lives. We have applied electron spin resonance (ESR) spectroscopy combined with spin traps using the probes PBN (N-tert-butyl-α-phenylnitrone) and DMPO (5,5-dimethyl-1-pyrrolineN-oxide) to assess free radical formation in the human pathogenStaphylococcus aureustreated with a bactericidal antibiotic, vancomycin or ciprofloxacin. While we were unable to detect ESR signals in bacterial cells, hydroxyl radicals were observed in the supernatant of bacterial cell cultures. Surprisingly, the strongest signal was detected in broth medium without bacterial cells present and it was mitigated by iron chelation or by addition of catalase, which catalyzes the decomposition of hydrogen peroxide to water and oxygen. This suggests that the signal originates from hydroxyl radicals formed by the Fenton reaction, in which iron is oxidized by hydrogen peroxide. Previously, hydroxyl radicals have been proposed to be generated within bacterial cells in response to bactericidal antibiotics. We found that whenS. aureuswas exposed to vancomycin or ciprofloxacin, hydroxyl radical formation in the broth was indeed increased compared to the level seen with untreated bacterial cells. However,S. aureuscells express catalase, and the antibiotic-mediated increase in hydroxyl radical formation was correlated with reducedkatAexpression and catalase activity in the presence of either antibiotic. Therefore, our results show that inS. aureus, bactericidal antibiotics modulate catalase expression, which in turn influences the formation of free radicals in the surrounding broth medium. If similar regulation is found in other bacterial species, it might explain why bactericidal antibiotics are perceived as inducing formation of free radicals.

Removal of Tributyltin in Shipyard Waters: Characterization and Treatment to Meet Low Parts per Trillion Levels

2003 ◽  
Vol 19 (03) ◽  
pp. 179-186
Author(s):  
Gary C. Schafran ◽  
R. Prasad ◽  
F. H. Thorn ◽  
R. Michael Ewing ◽  
J. Soles
Keyword(s):  
Hydrogen Peroxide ◽  
Activated Carbon ◽  
Hydroxyl Radical ◽  
Ultraviolet Irradiation ◽  
Treatment Plant ◽  
Full Scale ◽  
Radical Formation ◽  
Estuarine Waters ◽  
Treatment Conditions ◽  
Made In

Removal of tributyltin (TBT) from shipyard waters has been conducted in Virginia shipyards for over 2.5 years and has resulted in a 99% reduction of TBT discharged to coastal-estuarine waters. This has been achieved by conventional coagulation clarification for particulate TBT removal and removal of dissolved TBT using activated carbon. Although advances have been made in the understanding of TBT removal under various treatment conditions, TBT removal with the existing full-scale treatment plant to levels that would comply with a 50 parts per trillion (pptr) discharge limit are not possible. Results from study efforts that are currently ongoing suggest that the 50 pptr limit might be reached using ultraviolet irradiation or ozonation and that both processes would be substantially improved with the addition of hydrogen peroxide to promote hydroxyl radical formation.

Hydroxyl radical formation from bacteria-assisted Fenton chemistry at neutral pH under environmentally relevant conditions

2016 ◽  
Vol 13 (4) ◽  
pp. 757 ◽  
Author(s):  
Jarod N. Grossman ◽  
Tara F. Kahan
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Natural Waters ◽  
Shewanella Oneidensis ◽  
Radical Formation ◽  
Production Rates ◽  
Fenton Chemistry ◽  
Iron Reducing Bacteria ◽  
Neutral Ph ◽  
Reducing Bacteria

Environmental contextReactions in natural waters such as lakes and streams are thought to be extremely slow in the absence of sunlight (e.g. at night). We demonstrate that in the presence of iron, hydrogen peroxide and certain bacteria (all of which are common in natural waters), certain reactions may occur surprisingly quickly. These findings will help us predict the fate of many compounds, including pollutants, in natural waters at night. AbstractDark Fenton chemistry is an important source of hydroxyl radicals (OH•) in natural waters in the absence of sunlight. Hydroxyl radical production by this process is very slow in many bodies of water, owing to slow reduction and low solubility of FeIII at neutral and near-neutral pH. We have investigated the effects of the iron-reducing bacteria Shewanella oneidensis (SO) on OH• production rates from Fenton chemistry at environmentally relevant hydrogen peroxide (H2O2) and iron concentrations at neutral pH. In the presence of 2.0 × 10–4M H2O2, OH• production rates increased from 1.3 × 10–10 to 2.0 × 10–10Ms–1 in the presence of 7.0 × 106cellsmL–1 SO when iron (at a concentration of 100μM) was in the form of FeII, and from 3.6 × 10–11 to 2.2 × 10–10Ms–1 when iron was in the form of FeIII. This represents rate increases of factors of 1.5 and 6 respectively. We measured OH• production rates at a range of H2O2 concentrations and SO cell densities. Production rates depended linearly on both variables. We also demonstrate that bacteria-assisted Fenton chemistry can result in rapid degradation of aromatic pollutants such as anthracene. Our results suggest that iron-reducing bacteria such as SO may be important contributors to radical formation in dark natural waters.

Formation of Hydroxyl Radicals from Hydrogen Peroxide and Iron Salts by Superoxide- and Ascorbate-Dependent Mechanisms: Relevance to the Pathology of Rheumatoid Disease

1983 ◽  
Vol 64 (6) ◽  
pp. 649-653 ◽  
Author(s):  
D. A. Rowley ◽  
B. Halliwell
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Oxygen Radicals ◽  
Rheumatoid Disease ◽  
Iron Salts ◽  
Low Concentrations ◽  
Short Period ◽  
Generating System

1. Superoxide and hydrogen peroxide are formed by activated phagocytes and react together in the presence of iron salts to form the hydroxyl radical, which attacks hyaluronic acid. Ascorbic acid also interacts with hydrogen peroxide and iron salts to form hydroxyl radical in a reaction independent of superoxide. Since iron salts, ascorbate and activated phagocytes are present in the rheumatoid joint, experiments were designed to see whether ascorbate-dependent or superoxide-dependent formation of hydroxyl radicals would be more important in vivo. 2. in the present study, addition of ascorbate to a superoxide-generating system at concentrations of 100 μmol/l provoked a superoxide-independent formation of hydroxyl radicals for a short period. Lower concentrations of ascorbate did not do this. It is therefore suggested that the superoxide-dependent reaction is probably more important. 3. It is further suggested that destruction of ascorbate by oxygen radicals formed by activated phagocytes accounts for the previously reported low concentrations of this compound in the serum and synovial fluid of rheumatoid patients.

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