scholarly journals Kinetic study of hydroxyl radical formation in a continuous hydroxyl generation system

RSC Advances ◽  
2018 ◽  
Vol 8 (71) ◽  
pp. 40632-40638 ◽  
Author(s):  
Xin Wang ◽  
Long Zhang
Keyword(s):  
Hydroxyl Radical ◽  
Kinetic Study ◽  
Hydroxyl Radicals ◽  
Radical Formation ◽  
Generation System ◽  
Simple Apparatus ◽  
System P ◽  
Continuous Generation ◽  
First Time

A novel and simple apparatus for the continuous generation of hydroxyl radicals has been constructed for the first time.

scholarly journals Hydroxylation of salicylate by microsomal fractions and cytochrome P-450. Lack of production of 2,3-dihydroxybenzoate unless hydroxyl radical formation is permitted

1991 ◽  
Vol 276 (3) ◽  
pp. 753-757 ◽  
Author(s):  
M Ingelman-Sundberg ◽  
H Kaur ◽  
Y Terelius ◽  
J O Persson ◽  
B Halliwell
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Liver Microsomes ◽  
Iron Chelator ◽  
Radical Formation ◽  
Rabbit Liver ◽  
Nadph Cytochrome ◽  
Substrate Hydroxylation ◽  
Cytochrome P 450

Attack by hydroxyl radicals (.OH) upon salicylate (2-hydroxybenzoate) leads to formation of both 2,3-dihydroxybenzoate (2,3-DHB) and 2,5-dihydroxybenzoate (gentisate, 2,5-DHB). It has been suggested that formation of 2,3-DHB from salicylate is a means of monitoring .OH formation. Production of 2,3-DHB and 2,5-DHB by liver microsomal fractions and isoforms of cytochrome P-450 was investigated. Liver microsomes prepared from variously treated rats and rabbits catalysed the formation of 2,5-DHB but not 2,3-DHB. Formation of 2,5-DHB was inhibited by CO, metyrapone and SKF-525A, but not by the .OH scavengers mannitol and formate or by the iron chelator desferrioxamine. Purified P-450s IIE1, IIB4 or IA2 from rabbit liver microsomes, reconstituted together with NADPH-cytochrome P-450 reductase, led to formation of equal amounts of 2,3-DHB and 2,5-DHB in reactions that were almost completely inhibited by mannitol or formate. Addition of Fe3+/EDTA either to microsomes or to membranes containing reconstituted P-450 caused formation of approximately equal amounts of 2,3-DHB and 2,5-DHB, consistent with an .OH-dependent attack on salicylate. The data indicate that the microsomal P-450 system catalyses hydroxylation of salicylate to 2,5-DHB, but not formation of 2,3-DHB. Hence measurement of 2,3-DHB might provide a means of monitoring .OH formation. Care must be taken in studies of substrate hydroxylation by microsomes or reconstituted P-450 systems to avoid artefacts resulting from .OH generation.

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 Hydroxyl radical production induced by plasma hydrogenated nanodiamonds under X-ray irradiation

2017 ◽  
Vol 53 (7) ◽  
pp. 1237-1240 ◽  
Author(s):  
Magdalena Kurzyp ◽  
Hugues A. Girard ◽  
Yannis Cheref ◽  
Emilie Brun ◽  
Cecile Sicard-Roselli ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Detonation Nanodiamonds ◽  
X Ray ◽  
Radical Production ◽  
First Time

For the first time, overproduction of hydroxyl radicals (HO˙) induced by plasma hydrogenated detonation nanodiamonds (H-NDs) under X-ray irradiation is reported.

scholarly journals Green and facile production of high-quality graphene from graphite by the combination of hydroxyl radical and electrical exfoliation

RSC Advances ◽  
2018 ◽  
Vol 8 (71) ◽  
pp. 40621-40631 ◽  
Author(s):  
Xin Wang ◽  
Long Zhang
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Efficient Method ◽  
High Quality ◽  
Green Production ◽  
First Time

A novel, simple and efficient method, involving the combination of hydroxyl radicals and electrical exfoliation of graphite for the green production of high-quality graphene from graphite, was developed for the first time.

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.

Enhancement of hydroxyl radical generation by phenols and their reaction intermediates during ozonation

1998 ◽  
Vol 38 (6) ◽  
pp. 147-154 ◽  
Author(s):  
Hideo Utsumi ◽  
Sang-Kuk Han ◽  
Kazuhiro Ichikawa
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Spin Trapping ◽  
Active Species ◽  
Generation Rate ◽  
Peak Height Ratio ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Phenol Derivatives ◽  
Semiquinone Radicals

Generation of hydroxyl radicals, one of the major active species in ozonation of water was directly observed with a spin-trapping/electron spin resonance (ESR) technique using 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) as a spin-trapping reagent. Hydroxyl radical were trapped with DMPO as a stable radical, DMPO-OH. Eighty μM of ozone produced 1.08 X 10-6M of DMPO-OH, indicating that 1.4% of •OH is trapped with DMPO. Generation rate of DMPO-OH was determined by ESR/stopped-flow measurement. Phenol derivatives increased the amount and generation rate of DMPO-OH, indicating that phenol derivatives enhance •OH generation during ozonation of water. Ozonation of 2,3-, 2,5-, 2,6-dichlorophenol gave an ESR spectra of triplet lines whose peak height ratio were 1:2:1. ESR parameters of the triplet lines agreed with those of the corresponding dichloro-psemiquinone radical. Ozonation of 2,4,5- and 2,4,6-trichlorophenol gave the same spectra as those of 2,5- and 2,6-dichlorophenol, respectively, indicating that a chlorine group in p-position is substituted with a hydroxy group during ozonation. Amounts of the radical increased in an ozone-concentration dependent manner and were inhibited by addition of hydroxyl radical scavengers. These results suggest that p-semiquinone radicals are generated from the chlorophenols by hydroxyl radicals during ozonation. The p-semiquinone radicals were at least partly responsible for enhancements of DMPO-OH generation.

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