Electron Paramagnetic Resonance Spin Trapping Research Articles

The iron chelator Dp44mT does not protect myocytes against doxorubicin

The iron chelating agent Dp44mT (di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone) and the clinically approved cardioprotective agent dexrazoxane (ICRF-187) were compared for their ability to protect neonatal rat cardiac myocytes from doxorubicin-induced damage. Doxorubicin is thought to induce oxidative stress on the heart muscle through iron-mediated oxygen radical damage. While dexrazoxane was able to protect myocytes from doxorubicin-induced lactate dehydrogenase release, in contrast Dp44mT synergistically increased doxorubicin-induced damage. This occurred in spite of the fact that Dp44mT quickly and efficiently removed iron(III) from its complex with doxorubicin and that Dp44mT also rapidly entered myocytes and displaced iron from a fluorescence-quenched trapped intracellular iron-calcein complex. Electron paramagnetic resonance spin trapping was used to show that iron complexes of Dp44mT were not able to generate hydroxyl radicals, suggesting that its cytotoxicity was not due to reactive oxygen species formation. In conclusion Dp44mT is unlikely to be useful as an anthracycline cardioprotective agent.

Visualizing Chemical Reactions and Crossover Processes in a Fuel Cell Inserted in the ESR Resonator: Detection by Spin Trapping of Oxygen Radicals, Nafion-Derived Fragments, and Hydrogen and Deuterium Atoms

We present experiments in an in situ fuel cell (FC) inserted in the resonator of the ESR spectrometer that offered the ability to observe separately processes at anode and cathode sides and to monitor the formation of HO and HOO radicals, H and D atoms, and radical fragments derived from the Nafion membrane. The presence of the radicals was determined by spin-trapping electron spin resonance (ESR) with 5,5-dimethylpyrroline N-oxide (DMPO) as a spin trap. The in situ FC was operated at 300 K with a membrane-electrode assembly (MEA) based on Nafion 117 and Pt as catalyst, at closed and open circuit voltage conditions, CCV and OCV, respectively. Experiments with H(2) or D(2) at the anode and O(2) at the cathode were performed. The DMPO/OH adduct was detected only at the cathode for CCV operation, suggesting generation of hydroxyl radicals from H(2)O(2) formed electrochemically via the two-electron reduction of oxygen. The DMPO/OOH adduct, detected in this study for the first time in a FC, appeared at the cathode and anode for OCV operation, and at the cathode after CCV FC operation of >or=2 h. These results were interpreted in terms of electrochemical generation of HOO at the cathode (HO + H(2)O(2) --> H(2)O + HOO) and its chemical generation at the anode from hydrogen atoms and crossover oxygen (H + O(2) --> HOO). DMPO/H and DMPO/D adducts were detected at the anode and cathode sides, for CCV and OCV operation; H and D are aggressive radicals capable of abstracting fluorine from the tertiary carbon in the polymer membrane chain and of leading to chain fragmentation. Carbon-centered radical (CCR) adducts were detected at the cathode after CCV FC operation; weak CCR signals were also detected at the anode. CCRs can originate only from the Nafion membranes, and their presence indicates membrane fragmentation. Taken together, this study has demonstrated that FC operation involves processes such as gas crossover, reactions at the catalyst surface, and possible attack of the membrane by reactive H or D that do not occur in ex situ experiments in the laboratory, thus implying different mechanistic pathways in the two types of experiments.

Degradation of 2, 4-D acid using Mn2+ as catalyst under UV irradiation

In this paper, the oxidative degradation of 2, 4-dichlorophenoxyacetic acid (2, 4-D) using Mn2+/H2O2 reagent under UV irradiation was studied. The results show that 2, 4-D was degraded more completely in Mn2+/H2O2 solution than traditional Fenton solutions. The effects of the concentration of Mn2+, H2O2 and pH were also investigated. And under the optimal condition of \( c_{Mn^{2 + } } \) 1.48×10−4 mol/L, \( c_{H_2 O_2 } \) 8.99×10−5 mol/L and pH 3.38, the formation of ·OH was the most, both the decomposition rate of H2O2 and the degradation rate of 2, 4-D were the fastest. In addition, the photoreaction process was monitored using spin-trapping electron paramagnetic resonance (EPR), and the results indicated that the oxidative process was predominated mainly by the hydroxyl radical (·OH) gennerated in the system.

Partial oxidation of allylic and primary alcohols with O2 by photoexcited TiO2

Proper reaction conditions have been found for the conversion of geraniol, citronellol, trans-2-penten-1-ol and 1-pentanol to the corresponding aldehydes with good chemo-selectivity (>70%) by photochemical excitation of suspensions of P25-TiO(2). It is demonstrated that adsorption of the alcohol on the surface as an alcoholate is necessary for its oxidation. ESR-spin trapping experiments point out that oxidation of alcohols starts with the formation of alkoxide radicals. Water content in the dispersing medium strongly inhibits alcohol adsorption and subsequent oxidation. In fact, water increases the polarity of the dispersing medium favouring the affinity between the polar alcohol and the CH(3)CN-H(2)O mixture itself; moreover, water competitive adsorption with the alcohol causes the removal of the latter from the photocatalytic surface with consequent difficult oxidation, as evidenced by ESR-spin trapping investigation. The reactivity of the alcohol on the surface of photoexcited P25-TiO(2) is also affected by the nature of its hydrophobic aliphatic chain: geraniol and citronellol are more susceptible to the water content than their short analogues trans-2-penten-1-ol and 1-pentanol. Moreover, in anhydrous CH(3)CN, specific interaction between the surface and the OH group enhances the reactivity of the primary aliphatic alcohols towards their partial oxidation to aldehyde, which can be accumulated in the reaction environment.

Spin Trapping of Au−H Intermediate in the Alcohol Oxidation by Supported and Unsupported Gold Catalysts

Electron paramagnetic resonance (EPR) spectroscopy and spin trapping were used to explore the mechanism of alcohol oxidation over gold catalysts. Reaction of secondary alcohols with supported and unsupported gold catalysts (e.g., Au/CeO(2), polymer-incarcerated Au nanoparticles, PPh(3)-protected Au nanoparticles) in the presence of spin traps led to the formation of a hydrogen spin adduct. Using isotope labeling, we confirmed that the hydrogen in the spin adduct originates from the cleavage of the C-H bond in the alcohol molecule. The formation of the hydrogen spin adduct most likely results from the abstraction of hydrogen from the Au surface by a spin trap. These results thus strongly suggest intermediate formation of Au-H species during alcohol oxidation. The role of oxygen in this mechanism is to restore the catalytic activity rather than oxidize alcohol. This was further confirmed by carrying out gold-catalyzed alcohol oxidation in the absence of oxygen, with nitroxides as hydrogen abstractors. The support (e.g., metal oxides) can activate oxygen and act as an H abstractor from the gold surface and hence lead to a faster recovery of the activity. Peroxyl radicals were also observed during alcohol oxidation, consistent with a free-radical autoxidation mechanism. However, this mechanism is likely to be a minor side reaction, which does not lead to the formation of an appreciable amount of oxidation products.

Effect of Lewis base coordination on boryl radical reactivity: investigation using laser flash photolysis and kinetic ESR

AbstractThe effect of Lewis base coordination on boryl radical reactivity (L→BH where L is triethylamine, 2‐picoline, 4‐dimethylaminopyridine, quinoline and diphenyl phosphine) is examined. Direct detection of the different boryl radicals, their transient absorption spectra, their interaction with double or triple bonds, oxygen, oxidizing agent, alkyl halides and their hydrogen lability have been studied using laser flash photolysis (LFP), kinetic ESR (KESR), ESR spin trapping and MO calculations. For example, a strong decrease of both the bond dissociation energy (BDE)(BH) (33.8 kcal mol−1) and the addition rate constant to MA (1300 105 to >105 M−1 s−1) was noted when going from the triethylamine borane to the quinoline borane complex, in line with the spin delocalization (1.04 vs. 0.19). These structures are also proposed as new highly efficient co‐initiators for the acrylate photopolymerization. Copyright © 2009 John Wiley & Sons, Ltd.

Superoxide-mediated inactivation of nitric oxide and peroxynitrite formation by tobacco smoke in vascular endothelium: studies in cultured cells and smokers

Tobacco smoke is known to cause nitric oxide ((*)NO) inactivation and endothelial dysfunction. In this work we evaluated the interplay between (.)NO and superoxide (O(2)(*-)) radicals and the consequent impact on (*)NO bioavailability and nitroxidative stress in bovine aortic endothelial cells exposed to cigarette smoke extract (CSE) and in smokers. Bovine aortic endothelial cells in the presence of CSE triggered O(2)(*-) production as indicated by spin-trapping electron paramagnetic resonance experiments. O(2)(*-) was produced both extracellulary (3.4 vs. 1.0 nmol.h(-1)*mg(-1); CSE vs. control; cytochrome c(3+) reduction assay) and intracellularly (40% inhibition of cytosolic aconitase). CSE also led to the production of peroxynitrite as evaluated by dihydrorhodamine oxidation and protein tyrosine nitration on cells. O(2)(*-) and peroxynitrite formation were decreased by ascorbate and alpha-tocopherol. Additionally, CSE led to the oxidation of endothelial nitric oxide synthase increasing the monomeric inactive form of endothelial nitric oxide synthase. Smokers and age-matched healthy volunteers were supplemented orally with 500 mg ascorbate plus 400 IU all-rac-alpha-tocopherol every 12 h for 165 days. Smokers had endothelial dysfunction compared with control subjects (95% confidence interval: 2.5, 8.3 vs. 10.6, 14.2; P < 0.05) as assessed by flow-mediated dilation of the brachial artery, and plasma levels of protein 3-nitrotyrosine were 1.4-fold higher. The loss of flow-mediated dilation in smokers reverted after a long-term antioxidant supplementation (95% confidence interval: 13.9, 19.9; P < 0.05), reaching values comparable with the control population. Our data indicate that elements on tobacco smoke, most likely through redox cycling, divert (*)NO toward peroxynitrite by inducing O(2)(*-) production in vascular endothelial cells both in vitro and in vivo.

Identification of Free Radical Intermediates in Oxidized Wine Using Electron Paramagnetic Resonance Spin Trapping

Free radicals are thought to be key intermediates in the oxidation of wine, but their nature has not been established. Electron paramagnetic resonance spectroscopy was used to detect and identify several free radical species in wine under oxidative conditions with the aid of spin traps. The 1-hydroxylethyl radical was the sole radical species observed when α-(4-pyridyl-1-oxide)-N-tert-butylnitrone was used as a spin trap in a heated (55 °C), low-sulfite (15 mg L(-1)) red wine. This radical appears to arise from ethanol oxidation via the hydroxyl radical, and this latter species was confirmed by using a high concentration (1.5 M) of the 5,5-dimethylpyrroline-N-oxide spin trap, thus providing the first direct evidence of the Fenton reaction in wine. Hydroxyl radical formation in wine was corroborated by converting hydroxyl radicals to methyl radicals by its reaction with dimethyl sulfoxide. The novel spin trap 5-tert-butoxycarbonyl 5-methyl-1-pyrroline N-oxide was also used in this study to identify sulfite radicals in wine for the first time. This spin trap has also been shown to trap hydroperoxyl radicals, the generation of which is predicted in wine; however, no evidence of this species was observed.

New insights into the detection of sulfur trioxide anion radical by spin trapping: radical trapping versus nucleophilic addition

It has recently been demonstrated that (bi)sulfite (hydrated sulfur dioxide) reacts with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) via a nonradical, nucleophilic reaction, and further proposed that the radical adduct (DMPO/ SO 3 −) formation in biological systems is an artifact and not the result of spin trapping of sulfur trioxide anion radical ( SO 3 −). Here, the one-electron oxidation of (bi)sulfite catalyzed by horseradish peroxidase/H 2O 2 has been reinvestigated by ESR spin trapping with DMPO and oxygen uptake studies to obtain further evidence for the radical reaction mechanism. In the case of ESR experiments, the signal of the DMPO/ SO 3 − radical adduct was detected, and the initial rate of its formation was calculated. Support for the radical pathway via SO 3 − was obtained from the stoichiometry between the amount of consumed molecular oxygen and the amount of (bi)sulfite oxidized to sulfate (SO 4 2−). When DMPO was incubated with (bi)sulfite, oxygen consumption was completely inhibited owing to the efficiency of DMPO trapping. In the absence of DMPO, the initial rate of oxygen and H 2O 2 consumption was determined to be half of the initial rate of DMPO/ SO 3 − radical adduct formation as determined by ESR, demonstrating that DMPO forms the radical adduct by trapping the SO 3 − exclusively. We conclude that DMPO is not susceptible to artifacts arising from nonradical chemistry (nucleophilic addition) except when both (bi)sulfite and DMPO concentrations are at nonphysiological levels of at least 0.1 M and the incubations are for longer times.

Scavenging of superoxide anion radical and hydroxyl radical by novel thiazolyl‐thiazolidine‐2,4‐dione compounds

The antioxidant behavior of a series of new synthesized substituted thiazolyl-thiazolidine-2,4-dione compounds (TZDs) was examined using chemiluminescence and electron paramagnetic resonance spin trapping techniques. 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO) was used as the spin trap. The reactivity of TZDs with superoxide anion radical (O2(*-)) and hydroxyl radical (HO(*)) was evaluated using potassium superoxide/18-crown-6 ether dissolved in dimethylsulfoxide, and the Fenton-like reaction (Fe(2+) + H2O2), respectively. The results showed that TZDs efficiently inhibited light emission from the O2(*-) generating system at a concentration of 0.05-1 mmol L(-1) (5-94% reductions were found at 1 mmol L(-1) concentration). The TZD compounds showed inhibition of HO(*)-dependent DMPO-OH spin adduct formation from DMPO (the amplitude decrease ranged from 8 to 82% at 1 mmol L(-1) concentration). The findings showed that examined TZDs had effective activities as radical scavengers.

Effects of methylarginines on superoxide production from uncoupled eNOS.

The endogenous methylarginines, asymmetric dimethylarginine (ADMA) and NG‐monomethyl‐L‐arginine (L‐NMMA) regulate nitric oxide (NO) production from endothelial NO synthase (eNOS). Under conditions of tetrahydrobiopterin (BH4) depletion eNOS generates ▸O2‐, however, the effects of methylarginines on eNOS‐derived ▸O2‐ generation are poorly understood. Therefore, using electron paramagnetic resonance spin trapping techniques we measured the dose‐dependent effects of ADMA and L‐NMMA on ▸O2‐ production from eNOS under conditions of BH4 depletion. In the absence of BH4, ADMA dose‐dependently increased NOS‐derived ▸O2‐ generation, with a maximal increase of 151 % at 100 uM. L‐NMMA also dose‐dependently increased NOS‐derived ▸O2‐, but to a lesser extent, demonstrating a 102 % increase at 100 uM L‐NMMA. Moreover, methylarginines also increased eNOS derived ROS from endothelial cells. Measurements of NADPH consumption from eNOS demonstrated that binding of methylarginines increased the rate of NADPH oxidation. Spectrophotometric studies demonstrate that the binding of ADMA and L‐NMMA shifts the eNOS heme to the high‐spin state, enabling enhanced electron transfer from the reductase to the oxygenase site. These results demonstrate that the methylarginines can profoundly shift the balance of NO and ▸O2‐ generation from eNOS and play an important role in endothelial dysfucntion.

Tooth Bleaching with Nonthermal Atmospheric Pressure Plasma

We demonstrated that room temperature plasma could be used for tooth bleaching. A nonthermal, atmospheric pressure, helium plasma jet device was developed to enhance the tooth bleaching effect of hydrogen peroxide (H 2O 2). All teeth were sectioned sagittally into halves, which were assigned randomly to either the experimental group or the control group. The experimental group was treated with H 2O 2 (28%, 20 μL every 30 seconds) plus plasma (5 W) for 10 minutes; the control group was treated with H 2O 2 alone for the same duration. Removal of the tooth surface protein was demonstrated by scanning electron microscopy images and Ponceau staining. Production of hydroxyl radicals (·OH) was measured by using electron spin resonance spin-trapping. Combining plasma and H 2O 2 improved the bleaching efficacy by a factor of 3 compared with using H 2O 2 alone. Tooth surface proteins were noticeably removed by plasma treatment. When a piece of tooth was added to a solution of H 2O 2 as a catalyst, production of ·OH after plasma treatment was 1.9 times greater than when using H 2O 2 alone. We suggest that the improvement in tooth bleaching induced by plasma is due to the removal of tooth surface proteins and to increased ·OH production.

Fabrication and photo-electrocatalytic properties of highly oriented titania nanotube arrays with {1 0 1} crystal face

Highly oriented titania nanotube (TN) arrays with {1 0 1} crystal face were prepared on the surface of titanium substrate by liquid chemical deposition method. The obtained titania samples were characterized by X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), BET measurements, diffuse reflectance spectroscopy (DRS), and electron paramagnetic resonance (EPR) spin trap technique. Results indicate that the nanotubes grown in this study are well-aligned and organized into high-density uniform arrays. The typical dimensions of the hollow tube are ∼90 nm in outer diameter, ∼60 nm in inner diameter, ∼15 nm in wall thickness and ∼300 nm in height. The BET surface area of the obtained titania nanotube is 275 m 2/g. The EPR signals reveal that hydroxyl radical ( OH) species can be produced in the nanotube system, and no OH radical EPR signals were detected under dark and/or nanotube non-existing situations. The catalytic degradation of a textile azo dye, acid orange 7 (AO7), in aqueous solution with titania nanotube arrays electrode was carried out using photo-electrocatalytic (PEC) process, comparing with electrochemical process (EP) and photocatalytic (PC) process. A significant photo-electrochemical synergetic effect was observed, which is due to the efficient charge separation and transfer at the surface-interface of titania nanotube arrays. The kinetic constant of PEC degradation of AO7 using TN electrode was 48.7%, which is higher than that using P-25 TiO 2 film and TiO 2 particular film electrode. The enhanced degradation rate of AO7 using titania nanotube arrays could be attributed to their larger specific surface area and nanotubular structure with preferred reactive crystal face, which would increase their absorption capacity to the targeted substrates and the rate of surface-interface charge transfers in titania nanotube semiconductor redox systems.

Visible-Light-Induced Photocatalytic Oxidation of Polycyclic Aromatic Hydrocarbons over Tantalum Oxynitride Photocatalysts

The photooxidations of five typical polycyclic aromatic hydrocarbons (PAHs) were investigated by using tantalum oxynitride and Pt-tantalum oxynitride as visible light-driven photocatalysts. The electron paramagnetic resonance spin-trap technique and hydrogen peroxide test strip were used to monitor active species formed in these photocatalytic systems. Moreover, the participations of HO*, O2(-*) anions, and holes were further examined by adding their scavengers t-butanol, benzoquinone, and iodine anions, respectively. The reaction intermediates were analyzed by gas chromatography-mass spectrometer (GC-MS). The results show that tantalum oxynitride exhibits good photocatalytic activity for the PAHs photodegradation and the activity is greatly promoted by loading cocatalyst Pt. After 6 h visible light irradiation, phenanthrene, anthracene, benzo[a]anthracene, and acenaphthene can be completely oxidized over Pt-tantalum oxynitride. Under UV light irradiation, the photodegradation rate of PHE over Pt-tantalum oxynitride is 8 times faster than that over titanium dioxide (P25, 80% anatase, 20% rutile). Oxygen plays a crucial role on the photooxidations of PAHs. t-Butanol and benzoquinone almost have no effect on PAHs photodegradations, which indicate that HO* and O2(-*) anions play a negligible role on the photodegradations of PAHs. However, the presence of iodide anions significantly inhibits these degradation reactions, implying the crucial effect of holes on the photocatalytic systems. The PAHs degradations could therefore be attributed to the formation of holes in these systems. Based on the GC-MS analysis, the possible photooxidation pathways of PAHs were also proposed.

Light-assisted decomposition of dyes over iron-bearing soil clays in the presence of H 2O 2

Four types of soil clays from different sites in China have been chosen to simulate chemical remediation of soils contaminated with dyes by light-assisted Fenton-like method. X-Ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS) and electron spin resonance (ESR) measurements indicated that these soil clays contain iron oxides such as magnetite and hematite, where nondistorted iron active sites (ESR spectra, g = 2.3) predominate. Upon visible or UV irradiation, the soil clays were very effective for the degradation of nonbiodegradable cationic dyes such as Rhodamine B (RhB) by activating H 2O 2 at neutral pH. The photodegradation rates of RhB were closely related to total Fe content in clays and H 2O 2 dosage, indicating the mineral-catalyzed Fenton-like reactions operated. Soil organic matters (SOM) would remarkably inhibit the photodecomposition of RhB dye. The reaction products were some low-molecular-weight dicarboxylic acids and their derivatives, all of which are easily biodegradable. A possible mechanism was proposed based on the results obtained by spin-trapping ESR technique.

Increased labile iron pool in sorghum embryonic axes after the exogenous application of nitric oxide is independent on the nature of the NO donor

The objective of this work was to explore the hypothesis that nitric oxide (NO) affects Fe bioavailability in sorghum (Sorghum bicolor (L.) Moench) embryonic axes. NO content was assessed in embryonic axes isolated from seeds control or exposed to NO-donors, employing spin trapping electron paramagnetic resonance (EPR) methodology. NO donors such as sodium nitroprusside (SNP) and diethylenetriamine NONOate (DETA NONOate), released NO that permeated inside the axes increasing NO content. Under these conditions low temperature EPR was employed to study the labile iron pool. A 2.5 fold increase was observed in NO steady state concentration after 24 h of exposure to NO donors that was correlated to a 2 fold increase in the Fe labile pool, as compared to control axes. This observation provides experimental evidence for a potential role of NO in Fe homeostasis.

Ozone enhanced activity of aqueous titanium dioxide suspensions for photodegradation of 4-chloronitrobenzene

The TiO 2/UV/O 3 process has been employed to remove 4-chloronitrobenzene (4-CNB) and compared to UV/air, O 3, TiO 2/O 3, TiO 2/UV/O 2 and UV/O 3 five parallel oxidation pathways. The reaction activities of these six processes were tested in aqueous using electron paramagnetic resonance (EPR) spin trapping technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin trap. Moreover, the effects of ozone dosage, catalyst dosage and initial solution pH on the degradation of 4-CNB by TiO 2/UV/O 3 process were also investigated. Results showed that the TiO 2/UV/O 3 is the most efficient process for complete mineralization of 4-CNB since the combination of photocatalytic oxidation with ozone has a synergistic effect. The relative intensity of DMPO- OH follows the order of UV/air < O 3 < TiO 2/O 3 < UV/O 3 < TiO 2/UV/O 2 < TiO 2/UV/O 3. In TiO 2/UV/O 3 process, the ozone and catalyst dosage are found to have a significant impact on the process efficiency whereas initial pH has relatively less effect. Chlorine atoms of 4-CNB are absolutely oxidized to chloride anions when the ozone dosage in the range of 5–18 mg/min, or the catalyst dosage ranging from 1.0 to 2.0 g/L. Part of chloride anions would be further oxidized to chlorate(V) ions if the ozone dosage exceeds 24 mg/min, or the catalyst dosage exceeds 2.0 g/L.

Acylgermanes: Excited state processes and reactivity

The excited state processes of an acetyltriphenylgermane as well as the generation and the reactivity of the germyl radical are studied by laser flash photolysis, ESR spin trapping experiments and MO calculations. The transient spectra, the dissociation quantum yield, the singlet excited state S 1 lifetime, the S 1 quenching by an iodonium salt, the triplet state energy level E T, the Ge–C bond dissociation energy BDE, the interaction of the germyl radical with oxygen, double bonds and an iodonium salt, and the ESR spectra are determined. A triplet cleavage process is clearly evidenced; a singlet cleavage should likely contribute. The overall reactivity is discussed and compared to that of parent compounds. The acetyltriphenylgermane behaves as a high performance photoinitiator in the free radical polymerization and free radical promoted cationic polymerizations.

Serum Hydroxyl Radical Scavenging Capacity as Quantified with Iron-Free Hydroxyl Radical Source

We have developed a simple ESR spin trapping based method for hydroxyl (OH) radical scavenging-capacity determination, using iron-free OH radical source. Instead of the widely used Fenton reaction, a short (typically 5 seconds) in situ UV-photolysis of a dilute hydrogen peroxide aqueous solution was employed to generate reproducible amounts of OH radicals. ESR spin trapping was applied to quantify OH radicals; the decrease in the OH radical level due to the specimen’s scavenging activity was converted into the OH radical scavenging capacity (rate). The validity of the method was confirmed in pure antioxidants, and the agreement with the previous data was satisfactory. In the second half of this work, the new method was applied to the sera of chronic renal failure (CRF) patients. We show for the first time that after hemodialysis, OH radical scavenging capacity of the CRF serum was restored to the level of healthy control. This method is simple and rapid, and the low concentration hydrogen peroxide is the only chemical added to the system, that could eliminate the complexity of iron-involved Fenton reactions or the use of the pulse-radiolysis system.

Spin-Trapping ESR Detection of OH Radicals Generated in the Electrode Reactions for PEFCs

Spin-Trapping ESR Detection of OH Radicals Generated in the Electrode Reactions for PEFCs