scholarly journals Superoxide-dependent and ascorbate-dependent formation of hydroxyl radicals from hydrogen peroxide in the presence of iron. Are lactoferrin and transferrin promoters of hydroxyl-radical generation?

1987 ◽  
Vol 241 (1) ◽  
pp. 273-278 ◽  
Author(s):  
O I Aruoma ◽  
B Halliwell
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Chelating Agents ◽  
Acidic Ph ◽  
Iron Ion ◽  
Ph Values ◽  
Protective Ability ◽  
Ferritin Iron ◽  
Radical Generation ◽  
Ionic Iron

Apo-lactoferrin and apo-transferrin protect against iron-ion-dependent hydroxyl-radical (.OH) generation from H2O2 in the presence of superoxide radicals or ascorbic acid at pH 7.4, whether the necessary iron is added as ionic iron or as ferritin. Iron-loaded transferrin and lactoferrin [2 mol of Fe(III)/mol] show no protective ability, but do not themselves accelerate .OH production unless chelating agents are present in the reaction mixture, especially if the proteins are incorrectly loaded with iron. At acidic pH values, the protective ability of the apoproteins is diminished, and the fully iron-loaded proteins can release some iron in a form able to accelerate .OH generation. The physiological significance of these observations is discussed.

Myocardial alterations due to free-radical generation

1984 ◽  
Vol 246 (6) ◽  
pp. H776-H783 ◽  
Author(s):  
K. P. Burton ◽  
J. M. McCord ◽  
G. Ghai
Keyword(s):  
Endothelial Cells ◽  
Free Radicals ◽  
Hydroxyl Radical ◽  
Cardiac Myocytes ◽  
Hydroxyl Radicals ◽  
Vascular Endothelial Cells ◽  
Tissue Injury ◽  
Myocardial Damage ◽  
Vascular Endothelial ◽  
Radical Generation

Oxygen-derived free radicals have been proposed as general mediators of tissue injury in a variety of disease states. Recent interest has focused on the possibility that free radicals may be involved in ischemic myocardial damage. However, the exact types of damage that result from myocardial exposure to free radicals remains to be established. The purpose of this study was to evaluate the effects of superoxide and hydroxyl radicals on myocardial structure and function in an isolated perfused rabbit interventricular septal preparation. Superoxide was generated by adding purine (2.3 mM) and xanthine oxidase (0.01 U/ml) to the physiological solutions perfusing the septa. Hydroxyl radical generation was catalyzed by the addition of 2.4 microM Fe3+-loaded transferrin to the system. Exposure of normal septa to superoxide-generating solutions resulted in the development of structural alterations in the vascular endothelium including the development of vacuoles. Membranous cellular debris was evident in the extracellular space and within the vessels. Cardiac myocytes showed evidence of mild alterations. Exposure of septa to solutions capable of generating hydroxyl radicals resulted in more extensive and severe damage. Vascular endothelial cells showed evidence of vacuoles or blebs and edema. Severe swelling of mitochondria was evident in cardiac myocytes and vascular endothelial cells. In addition, myocytes often showed blebbing of the basement membrane. Normal septa exposed to superoxide showed no significant decrease in developed tension, whereas hydroxyl radical exposure resulted in a significant decrease in myocardial function.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Quantitative measurements of hydroxyl radicals generated by irradiated titanium dioxide nanoparticle suspensions

2019 ◽  
Author(s):  
Jason A. Coral ◽  
Christopher L. Kitchens
Keyword(s):  
Titanium Dioxide ◽  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Light Transmission ◽  
Generation Rate ◽  
Environmental Implications ◽  
Titanium Dioxide Nanoparticle ◽  
Increased Risk ◽  
Radical Generation ◽  
Exposure Conditions

ABSTRACTIncreased use of titanium dioxide (TiO2) nanoparticles in different applications has increased risk for adverse environmental implications based on an elevated likelihood of organism exposure. Anatase TiO2 is photoactive with exposure to ultraviolet light. TiO2 nanoparticle exposure to UV-A radiation in aquatic environments generates hydroxyl radical species, which may ultimately be responsible increased organism toxicity. The present research demonstrates that the rate of radical generation heavily depends on exposure conditions, particularly the presence of natural organic matter (NOM). Environmentally relevant concentrations of TiO2 nanoparticles were co-exposed to increasing NOM amounts (measured as concentration of dissolved organic carbon (DOC)) and UV-A intensities. Hydroxyl radical generation rate was determined using fluorescence spectroscopy. Radical generation rate was positively correlated to increases in TiO2 concentration and UV-A intensity, and negatively correlated to increased DOC concentration. Nanoparticle aggregation over time and decrease in light transmission from NOM had negligible contributions to the generation rate. This suggests the decreased radical generation rate is a result of radical quenching by NOM functionalities. D. magna toxicity to hydroxyl radicals is also demonstrated to decreased following the addition of DOC. These results correlate with the rate generation data, indicating that DOC provides rate attenuation that is protection to organisms. These conclusions demonstrate the importance considering exposure conditions during TiO2 toxicity testing, and during TiO2 waste management and regulatory decisions.

scholarly journals UV and Visible Light-Driven Production of Hydroxyl Radicals by Reduced Forms of N, F, and P Codoped Titanium Dioxide

Molecules ◽  
2019 ◽  
Vol 24 (11) ◽  
pp. 2147 ◽  
Author(s):  
A. M. Abdullah ◽  
Miguel Á. Garcia-Pinilla ◽  
Suresh C. Pillai ◽  
Kevin O'Shea
Keyword(s):  
Titanium Dioxide ◽  
Surface Modification ◽  
Visible Light ◽  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Visible Light Irradiation ◽  
Light Irradiation ◽  
Degussa P25 ◽  
Radical Generation ◽  
Reduced Forms

The photocatalytic activities of reduced titanium dioxide (TiO2) materials have been investigated by measuring their ability to produce hydroxyl radicals under UV and visible light irradiation. Degussa P25 TiO2 was doped with nitrogen (N), fluorine (F), and/or phosphorus (P) and then subjected to surface modification employing a thermo-physicochemical process in the presence of reducing agent sodium borohydride (NaBH4). The reduced TiO2 materials were characterized by a number of X-ray, spectroscopic and imaging methods. Surface doping of TiO2 was employed to modulate the band gap energies into the visible wavelength region for better overlap with the solar spectrum. Hydroxyl radical generation, central to TiO2 photocatalytic water purification applications, was quantitated using coumarin as a trap under UV and visible light irradiation of the reduced TiO2 materials. At 350 nm irradiation, the yield of hydroxyl radicals generated by the reduced forms of TiO2 was nearly 90% of hydroxyl radicals generated by the Degussa P25 TiO2. Hydroxyl radical generation by these reduced forms of TiO2 was also observed under visible light irradiation (419 and 450 nm). These results demonstrated that simple surface modification of doped TiO2 can lead to visible light activity, which is important for more economical solar-driven applications of TiO2 photocatalysis.

scholarly journals Effect of Shikonin and Alkannin on Hydroxyl Radical Generation System Concerned with Iron Ion

1998 ◽  
Vol 118 (12) ◽  
pp. 609-615 ◽  
Author(s):  
Takashi SEKINE ◽  
Toshiki MASUMIZU ◽  
Yoshie MAITANI ◽  
Kozo TAKAYAMA ◽  
Masahiro KOHNO ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Iron Ion ◽  
Generation System ◽  
Radical Generation

Detection of Hydroxyl Radicals by -Phenylalanine Hydroxylation: A Specific Assay for Hydroxyl Radical Generation in Biological Systems

2001 ◽  
Vol 290 (1) ◽  
pp. 138-145 ◽  
Author(s):  
Roberto Biondi ◽  
Yong Xia ◽  
Ruggero Rossi ◽  
Nazareno Paolocci ◽  
Giuseppe Ambrosio ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Biological Systems ◽  
Specific Assay ◽  
Radical Generation

scholarly journals Hydroxylation of aromatic compounds by reduced nicotinamide-adenine dinucleotide and phenazine methosulphate requires hydrogen peroxide and hydroxyl radicals, but not superoxide

1977 ◽  
Vol 167 (1) ◽  
pp. 317-320 ◽  
Author(s):  
B Halliwell
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radicals ◽  
Aromatic Compounds ◽  
Nicotinamide Adenine Dinucleotide ◽  
Acidic Ph ◽  
Aromatic Rings ◽  
Ph Values ◽  
Superoxide Dismutase 3 ◽  
Reduced Nicotinamide Adenine Dinucleotide ◽  
Phenazine Methosulphate

1. A mixture of NADH and phenazine methosulphate hydroxylates aromatic compounds at acidic pH values. 2. Hydroxylation is inhibited by catalase and by scavengers of the hydroxyl radical (-OH) but not by superoxide dismutase. 3. It is concluded that neither O2 leads to nor HO2- is sufficiently reactive to hydroxylate aromatic rings.

Is the Acidic pH of the External Auditory Canal Playing a Significant Role in the Treatment of Acute Otitis Externa?

2018 ◽  
Vol 69 (8) ◽  
pp. 2304-2305
Author(s):  
Oana Ruxandra Iana ◽  
Dragos Cristian Stefanescu ◽  
Viorel Zainea ◽  
Razvan Hainarosie
Keyword(s):  
External Auditory Canal ◽  
Otitis Externa ◽  
Proton Pumps ◽  
Acidic Ph ◽  
External Ear ◽  
Ph Values ◽  
The World ◽  
Subcutaneous Tissues ◽  
Low Levels ◽  
Value Changes

Variable pH values for skin have been reported in the literature, all within the acidic range, varying from 4.0 up to 7. 0. The origin of the acidic pH remains conjectural, and several factors have been incriminated with this role, such as eccrine and sebaceous secretions as well as proton pumps. Keeping low levels of pH prevents microbial dispersal as well as multiplication. The skin in the external auditory canal is also covered with this acidic mantle with antimicrobial value. Changes of pH in the external ear can lead to acute otitis externa. This condition is defined by the inflammation and infection of the cutaneous and subcutaneous tissues of the external auditory canal. 10% of the world�s population may suffer from acute otitis externa at least once in their lifetime. This paper aims to consolidate the relevance of an acidic pH in the healthy external ear and its relation to the pathogenesis and treatment of otitis externa through a prospective and interventional clinical study on 80 patients who presented to the outpatient department at Prof. Dr D. Hociota ENT Institute in Buch

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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