Spin Trapping Of Hydroxyl Radicals Research Articles

Spin trapping of hydroxyl radicals on Cu/HY zeolites suspended in aqueous solution

Hydroxyl radical intermediates are trapped in calcined Cu/HY zeolites in the presence of oxygen and water. This suggests that hydrogen peroxide is formed in situ from oxygen. Brønsted acids enhance the formation of the radicals.

Theoretical Study of the Spin Trapping of Hydroxyl Radical by Cyclic Nitrones: A Density Functional Theory Approach

The hydroxyl radical (*OH) is an important mediator of biological oxidative stress, and this has stimulated interest in its detection. 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) and its alkoxycarbonyl and alkoxyphosphoryl analogues have been employed as spin traps for electron paramagnetic resonance (EPR) spectroscopic radical detection. Energies of optimized geometries of nitrones and their corresponding *OH adducts were calculated using density functional theory (DFT) at the B3LYP/6-31+G//B3LYP/6-31G level. Calculations predict that the trans adduct formation is favored in alkoxycarbonyl nitrones, while cis adducts with intramolecular H-bonding is favored for alkoxyphosphoryl nitrones. Addition of *OH to a phosphoryl-substituted nitrone is more exoergic than the carbonylated nitrones. Charge and spin densities on the nitrone spin traps were correlated with their rates of addition with *OH, and results show that the charge density on the nitronyl C, the site of *OH addition, is more positive in phosphorylated nitrones compared to DMPO and the alkoxycarbonyl nitrones. The dihedral angle between the beta-H and nitroxyl O bonds is smaller in phosphorylated nitrones, and that aspect appears to account for the longer half-lives of the spin adducts compared to those in DMPO and alkoxycarbonyl nitrones. Structures of nitrones with trifluoromethyl-, trifluoromethylcarbonyl-, methylsulfonyl-, trifluoromethylsulfonyl-, amido-, spiropentyl-, and spiroester substituents were optimized and their energies compared. Amido and spiroester nitrones were predicted to be the most suitable nitrones for spin trapping of *OH due to the similarity of their thermodynamic and electronic properties to those of alkoxyphosphoryl nitrones. Moreover, dimethoxyphosphoryl substitution at C-5 was found to be the most efficient substitution site for spin trapping of *OH, and their spin adducts are predicted to be the most stable of all of the isomeric forms.

Fenton-dependent damage to carbohydrates: free radical scavenging activity of some simple sugars.

The antioxidant properties of simple carbohydrates were studied in a chemical system. Hydroxyl radicals generated by a Fenton reaction induce damage on simple carbohydrates with a consequent free radical scavenging activity. Carbohydrate activities were measured by different methods as spin-trapping of hydroxyl radical and electron paramagnetic resonance detection and 1,1-diphenyl-2-picrylhydrazyl quenching. Carbohydrate damage was evaluated in a Fenton system by measuring the reactive substances to thiobarbituric acid, by their decreased detection with an HPLC test, and by a gas chromatographic determination of formic acid from sugar oxidation. Different intensities of damage and scavenging were found according to molecular structure, and some hyphotheses on the carbohydrate action against free radicals were attempted. The assayed disaccharides were shown to be more active toward and less damaged by hydroxyl radical than monosaccharides.

Effect of thermal treatments on antioxidant and antiradical activity of blood orange juice

Abstract Blood orange juice is noted for its antioxidant properties, due to its rich phenolic profile. Orange segments were subjected to brief thermal treatments before transformation into juice, and changes in antioxidant and chemical composition were evaluated. Thermal treatment generally induced an increase in the main phenolic substances of orange juice, such as anthocyanins and total cinnamates, while ascorbic acid underwent a decrease. Antioxidant properties, evaluated in a lipoxygenase–linoleic acid system, were higher in thermally-treated samples, while free radical scavenging activity, evaluated by ESR spin trapping of hydroxyl radical and DPPH· quenching, were enhanced in untreated juices. A possible relationship between the changes in composition and the changes in antioxidant and antiradical properties is suggested.

ESR spin trapping of hydroxyl radicals in aqueous solution irradiated with high-LET carbon-ion beams.

The aim of this study was to quantify the hydroxyl radicals (*OH) produced when aqueous solutions are decomposed by high-linear energy transfer (LET) 290 MeV/nucleon carbon-ion beams using an electron spin resonance (ESR) spectrometer. Aerated cell culture medium containing 200 mM 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was irradiated with doses of 0 to 20 Gy with an LET of 20 to 90 keV/ micro m. We were able to obtain ESR spectra 10 min after irradiation, and the formation of *OH and hydrogen atoms was confirmed by radiolysis of deuterium oxide and ethanol containing DMPO. Our results showed that the yield of *OH by carbon-ion radiolysis increased in proportion to the absorbed dose over the range of 0 to 20 Gy. Furthermore, we discovered that the yield of *OH decreased linearity as LET increased logarithmically from 20 to 90 keV/ micro m. The generation of *OH by carbon-ion radiolysis at LETs of 20, 40, 60, 80 and 90 keV/ micro m was 64, 58, 52, 49 and 50%, respectively, of that for low-LET X radiolysis. These unique findings provide a further understanding of the indirect effect of high-LET radiation.

Synthesis of alpha-aryl N-adamant-1-yl nitrones and using them for spin trapping of hydroxyl radicals.

alpha-Aryl N-adamant-1-yl nitrones were synthesized and evaluated with respect to the stability of the hydroxyl radical adduct. The polarity and water solubility of nitrones were altered with changing the alpha-aryl groups. Introduction of adamantane ring instead of tert-butyl group resulted in a reasonable good stability of hydroxyl radical adduct for biological measurements.

Spin trapping of hydroxyl radical by 2H-imidazole-1-oxides

Spin trapping of hydroxyl radical by 2H-imidazole-1-oxides

When are metal ion-dependent hydroxyl and alkoxyl radical adducts of 5,5-dimethyl-1-pyrroline N-oxide artifacts?

The formation of the 5,5-dimethyl-1-pyrroline N-oxide ( DMPO . OH ) adduct of the spin trap DMPO has been reported to occur through nucleophilic addition of water in the presence of aqueous ferric chloride ( K. Makino, T. Hagiwara, A. Hagi, M. Nishi, and A. Murakami, 1990, Biochem. Biophys. Res. Commun. 172, 1073–1080 ). Due to the serious implications of these findings with respect to many spin trapping studies, the suitability of DMPO as a hydroxyl radical spin trap was studied in typical Fenton systems. Using 17O-enriched water, we show conclusively that nucleophilic addition of water occurs at the nitrone carbon (or C-2 position) of DMPO in the presence of either Fe or Cu ions. Furthermore, our results demonstrate that this nucleophilic reaction is a major pathway to the DMPO . OH adduct, even during the reaction of Fe(II) or Cu(I) with hydrogen peroxide. Primary alkoxyl adducts of DMPO also form in aqueous solution through nucleophilic addition in the presence of both Fe(III) and Cu(II). Attempts to obtain secondary and tertiary alkoxyl adducts by this mechanism were unsuccessful, possibly due to steric effects. When the reaction is carried out in various buffers, however, or in the presence of metal ion chelators, nucleophilic addition to DMPO from Fe(III) is effectively suppressed. Chelators also suppress the reaction with Cu(II). Hence, under most common experimental conditions in biochemical free radical research, nucleophilic addition to DMPO should not be of major concern.

Direct evidence for inhibition of free radical formation from Cu(I) and hydrogen peroxide by glutathione and other potential ligands using the EPR spin-trapping technique

Copper-induced oxidative damage is generally attributed to the formation of the highly reactive hydroxyl radical by a mechanism analogous to the Haber-Weiss cycle for Fe(II) and H 2O 2. In the present work, the reaction between the Cu(I) ion and H 2O 2 is studied using the EPR spin-trapping technique. The hydroxyl radical adduct was observed when Cu(I), dissolved in acetonitrile under N 2, was added to pH 7.4 phosphate buffer containing 100 m m 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Formation of the hydroxyl radical was dependent on the presence of O 2 and subsequent formation of H 2O 2. The k scav k DMPO ratios obtained were below those expected for a mechanism involving free hydroxyl radical and reflect the interference of nucleophilic addition of H 2O to DMPO to form the DMPO/ .OH adduct in the presence of nonchelated copper ion. Addition of ethanol or dimethyl sulfoxide to the reaction suggests that a high-valent metal intermediate, possibly Cu(III), was also formed. Spin trapping of hydroxyl radical was almost completely inhibited upon addition of Cu(I) to a solution of either nitrilotriacetate or histidine, even though the copper was fully oxidized to Cu(II) and H 2O 2 was formed. Bathocuproinedisulfonate, thiourea, and reduced glutathione all stabilized the Cu(I) ion toward oxidation by O 2. Upon addition of H 2O 2, the Cu(I) in all three complexes was oxidized to varying degrees; however, only the thiourea complex was fully oxidized within 2 min of reaction and produced detectable hydroxyl radicals. No radicals were detected from the bathocuproinedisulfonate or glutathione complexes. Overall, these results suggest that the deleterious effects of copper ions in vivo are diminished by biochemical chelators, especially glutathione, which probably has a major roll in moderating the toxicological effects of copper.

Light-dependent spin trapping of hydroxyl radical from human erythrocytes

The generation of reactive oxygen species from human erythrocytes has previously been demonstrated. Furthermore, erythrocytic protoporphyrin IX has been shown to generate superoxide and singlet oxygen when exposed to light. These findings suggest that a component of erythrocytic reactive oxygen species production may be light-dependent. By inhibiting erythrocyte superoxide dismutase, catalase, and glutathione peroxidase with N,N-diethyldithiocarbamate or sodium cyanide, we demonstrate the light-dependent generation of hydroxyl radical in human erythrocytes using spin trapping/Electron Spin Resonance spectroscopy. This finding may be significant in tissues where blood is exposed to light, such as in the eye.

Cautionary note for DMPO spin trapping in the presence of iron ion

2-Hydroxy-5,5-dimethyl-1-pyrrolidinyloxy (DMPO-OH), which is known to be produced by spin trapping of hydroxyl radicals (·OH) with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and has been a good monitor for detecting ·OH in biological systems, has been examined by EPR for its production scheme in the presence of iron ion. In an aqueous DMPO solution containing ferric ion (Fe 3+), DMPO-OH was produced and addition of methanol, a good scavenger for ·OH, to this solution led to an aminoxyl radical, DMPO-OCH3, instead of DMPO-CH2OH which is produced by DMPO spin trapping of ·CH2OH arising from H-abstraction by ·OH. Also EPR measurements at 77K indicated the formation of a chelate between DMPO and Fe 3+. Based on these, it has been elucidated that DMPO-OH as well as DMPO-OCH3 is formed by the nucleophilic attack of water and methanol to the chelating DMPO, respectively.

Electron spin resonance studies of the reaction of hypochlorite with 5,5-dimethyl-1-pyrroline- N-oxide

The reaction of hypochlorous acid with the spin trap, 5,5-dimethyl-1-pyrroline- N-oxide (DMPO) was found to yield 5,5-dimethyl-2-pyrrolidone- N-oxyl (DMPOX). In addition to DMPOX, 5,5-dimethyl-2-hydroxypyrrolidine- N-oxyl (DMPO-OH) and an unidentified chlorine-containing radical species were also observed under neutral and near-neutral conditions. Through the use of [ 17O]HOCl and the hydroxyl radical scavengers ethanol and formate, it was established that DMPO-OH was derived from hydration of DMPO rather than the spin-trapping of hydroxyl radical. Furthermore, kinetic studies and the incorporation of 17O showed that DMPO-OH was readily oxidized to DMPOX and that this reaction was acid and base catalyzed. Under strongly alkaline conditions, DMPOX reversibly formed another species, presumably the enolate, that had a four-line ESR signal identical to that of DMPO-OH. Eventually, carbon-centered adducts appeared whose ESR signals were consistent with the formation of DMPO condensation products.

Quantitative Aspects of ESR and Spin Trapping of Hydroxyl Radicals and Hydrogen Atoms in Gamma-Irradiated Aqueous Solutions

The efficiency of 5,5-dimethylpyrroline-1-N-oxide (DMPO) and alpha-(4-pyridyl-1-oxide)-N-tert.-butylnitrone (POBN) to spin trap hydroxyl radicals and hydrogen atoms, respectively, was studied in gamma-irradiated solutions where the radical yields are accurately known. The effects of dose, spin trap concentration, and pH and of the stability of the spin adducts on the spin-trapping efficiency were investigated. In degassed or N2-saturated solutions the spin-trapping efficiencies were 35% for DMPO and hydroxyl radicals and 14% for POBN and hydrogen atoms. The low spin-trapping efficiencies were shown not to be due to the instability of the DMPO-OH and POBN-H spin adducts or to the effects of H2O2 or O2. The low spin-trapping efficiency of DMPO may be explained by the reaction of hydroxyl radicals to abstract hydrogen from the DMPO molecule to produce carbon radicals as well as addition to the N = C double bond to form nitroxide radicals. For POBN the low spin-trapping efficiency for hydrogen atoms is explained in terms of addition reactions of hydrogen atoms to the aromatic ring and the pyridinium and nitrone oxygens.

Spin trapping of hydroxyl radical in the troposphere for determination by electron spin resonance and gas chromatography/mass spectrometry

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSpin trapping of hydroxyl radical in the troposphere for determination by electron spin resonance and gas chromatography/mass spectrometryTokuko. Watanabe, Masayuki. Yoshida, Shizuo. Fujiwara, Kazuhisa. Abe, Atsushi. Onoe, Minoru. Hirota, and Shunji. IgarashiCite this: Anal. Chem. 1982, 54, 14, 2470–2474Publication Date (Print):December 1, 1982Publication History Published online1 May 2002Published inissue 1 December 1982https://doi.org/10.1021/ac00251a015RIGHTS & PERMISSIONSArticle Views200Altmetric-Citations57LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (624 KB) Get e-Alerts Get e-Alerts