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Sample records for active hydroxyl radicals

  1. Vanadium promotes hydroxyl radical formation by activated human neutrophils.

    PubMed

    Fickl, Heidi; Theron, Annette J; Grimmer, Heidi; Oommen, Joyce; Ramafi, Grace J; Steel, Helen C; Visser, Susanna S; Anderson, Ronald

    2006-01-01

    This study was undertaken to investigate the effects of vanadium in the +2, +3, +4, and +5 valence states on superoxide generation, myeloperoxidase (MPO) activity, and hydroxyl radical formation by activated human neutrophils in vitro, using lucigenin-enhanced chemiluminescence (LECL), autoiodination, and electron spin resonance with 5,5-dimethyl-l-pyrroline N-oxide as the spin trap, respectively. At concentrations of up to 25 microM, vanadium, in the four different valence states used, did not affect the LECL responses of neutrophils activated with either the chemoattractant, N-formyl-l-methionyl-l-leucyl-l-phenylalanine (1 microM), or the phorbol ester, phorbol 12-myristate 12-acetate (25 ng/ml). However, exposure to vanadium in the +2, +3, and +4, but not the +5, valence states was accompanied by significant augmentation of hydroxyl radical formation by activated neutrophils and attenuation of MPO-mediated iodination. With respect to hydroxyl radical formation, similar effects were observed using cell-free systems containing either hydrogen peroxide (100 microM) or xanthine/xanthine oxidase together with vanadium (+2, +3, +4), while the activity of purified MPO was inhibited by the metal in these valence states. These results demonstrate that vanadium in the +2, +3, and +4 valence states interacts prooxidatively with human neutrophils, competing effectively with MPO for hydrogen peroxide to promote formation of the highly toxic hydroxyl radical.

  2. Redox regulation of protein tyrosine phosphatase activity by hydroxyl radical.

    PubMed

    Meng, Fan-Guo; Zhang, Zhong-Yin

    2013-01-01

    Substantial evidence suggests that transient production of reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) is an important signaling event triggered by the activation of various cell surface receptors. Major targets of H(2)O(2) include protein tyrosine phosphatases (PTPs). Oxidation of the active site Cys by H(2)O(2) abrogates PTP catalytic activity, thereby potentially furnishing a mechanism to ensure optimal tyrosine phosphorylation in response to a variety of physiological stimuli. Unfortunately, H(2)O(2) is poorly reactive in chemical terms and the second order rate constants for the H(2)O(2)-mediated PTP inactivation are ~10M(-1)s(-1), which is too slow to be compatible with the transient signaling events occurring at the physiological concentrations of H(2)O(2). We find that hydroxyl radical is produced from H(2)O(2) solutions in the absence of metal chelating agent by the Fenton reaction. We show that the hydroxyl radical is capable of inactivating the PTPs and the inactivation is active site directed, through oxidation of the catalytic Cys to sulfenic acid, which can be reduced by low molecular weight thiols. We also show that hydroxyl radical is a kinetically more efficient oxidant than H(2)O(2) for inactivating the PTPs. The second-order rate constants for the hydroxyl radical-mediated PTP inactivation are at least 2-3 orders of magnitude higher than those mediated by H(2)O(2) under the same conditions. Thus, hydroxyl radical generated in vivo may serve as a more physiologically relevant oxidizing agent for PTP inactivation. This article is part of a Special Issue entitled: Chemistry and mechanism of phosphatases, diesterases and triesterases.

  3. Hydroxyl radical reactions and the radical scavenging activity of β-carboline alkaloids.

    PubMed

    Herraiz, Tomás; Galisteo, Juan

    2015-04-01

    β-Carbolines are bioactive pyridoindole alkaloids occurring in foods, plants and the human body. Their activity as hydroxyl radical (OH) scavengers is reported here by using three different methods: deoxyribose degradation, hydroxylation of benzoate and hydroxylation of 2'-deoxyguanosine to give 8-hydroxy-2'-deoxyguanosine (8-OHdG) as assessed by RP-HPLC (MS). Fenton reactions (Fe(2+)/Fe(3+) plus H2O2) were used for OH generation, and the radical increased in the presence of ascorbic acid or 6-hydroxydopamine as pro-oxidants. β-Carbolines were scavengers of OH in the three assays and in the presence of pro-oxidants. Tetrahydro-β-carboline-3-carboxylic acids were active against the hydroxylation of 2'-deoxyguanosine. β-Carbolines reacted with hydroxyl radicals (OH) affording hydroxy-β-carbolines, whereas tetrahydro-β-carbolines gave oxidative and degradation products. On the basis of IC50 and reaction rates (k), β-carbolines (norharman and harman), and tetrahydro-β-carbolines (tetrahydro-β-carboline, 1-methyltetrahydro-β-carboline and pinoline) were good OH radical scavengers and their activity was comparable to that of the indole, melatonin, which is an effective hydroxyl radical scavenger and antioxidant.

  4. Production of hydroxyl radical by redox active flavonoids

    SciTech Connect

    Kalyanaraman, B.; Hodnick, W.F.; Pardini, R.S.

    1986-05-01

    The authors have previously shown that flavonoids autoxidize and generate superoxide (O/sub 2//sup -/) and hydrogen peroxide (H/sub 2/O/sub 2/), suggesting that hydroxyl radical (OH) could be formed via the metal-ion catalyzed Haber-Weiss reaction. In the presence of ethylenediamine tetraacetic acid (EDTA) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO), myricetin, quercetagetin and quercetin gave an ESR signal for the DMPO-OH spin adduct, and the DMPO-Eto adduct in the presence of excess ethanol, indicating the production of free OH. The addition of FeCl/sub 3/ to the reaction mixture resulted in a dramatic increase in the DMPO-OH signal. Without chelator (EDTA) there was no signal and the presence of diethylenetriamine-pentaacetic acid (DETAPAC) greatly diminished the signal. The presence of superoxide dismutase (SOD) had no effect on the signal while catalase completely abrogated the signal. The addition of Fe (III)-EDTA to flavonoid solutions under anaerobic conditions produced time dependent auxochromic shifts in their absorption spectra and resulted in the reduction of Fe (III) to Fe (II). These data suggest that the flavonoids autoxidize to produce O/sub 2//sup -/ and H/sub 2/O/sub 2/ by dismutation and in the presence of Fe (III)-EDTA the flavonoid can directly reduce the Fe (III) to Fe (II) resulting in the production of OH through Fenton chemistry.

  5. Chocolate consumption, fecal water antioxidant activity, and hydroxyl radical production.

    PubMed

    Record, Ian R; McInerney, Jennifer K; Noakes, Manny; Bird, Anthony R

    2003-01-01

    As part of a larger study into the effects of polyphenols derived from chocolate on bowel health we have compared the effects of consumption of chocolate containing either 200 mg of flavanols and related procyanidins or a similar chocolate containing less than 10 mg of polyphenols on fecal free radical production and antioxidant activity in 18 volunteers. In a double-blind crossover trail volunteers consumed chocolate for two 4-wk periods separated by a 4-wk washout period. During the time the volunteers consumed the chocolate they also consumed a low-polyphenol diet. Free radical production in the fecal water was lowered from 122 +/- 10 micromol/l/h to 94 +/- 9 micromol/l/h (P = 0.009) when the high procyanidin chocolate diet was consumed and from 117 +/- 14 micromol/l/h to 86 +/- 12 micromol/l/h when the low procyanidin chocolate was consumed (P = 0.014). Fecal water antioxidant capacity measured by either the Trolox equivalent antioxidant capacity or ferric reducing ability of plasma procedure was not significantly affected. Consumption of either chocolate reduced the production of free radicals in fecal water. This suggests that some component of the chocolate other than the flavanols and related procyanidins may have been effective.

  6. Novel spectroscopic sensor for the hydroxyl radical scavenging activity measurement of biological samples.

    PubMed

    Bekdeşer, Burcu; Özyürek, Mustafa; Güçlü, Kubilay; Apak, Reşat

    2012-09-15

    A novel spectroscopic sensor was developed and validated for hydroxyl radical scavenging (HRS) activity estimation using terephthalate (TP) as probe. This sensor was designed by electrostatic immobilization of the chromogenic oxidizing agent of the CUPric Reducing Antioxidant Capacity (CUPRAC) method, Cu(II)-Neocuproine (Cu(II)-Nc) complex, on a Nafion cation-exchange membrane, and the spectrophotometric assay developed in aqueous-alcoholic solutions was integrated to the CUPRAC sensor. Hydroxyl radicals ((•)OH) generated from an equivalent mixture of Fe(II)+EDTA with hydrogen peroxide attacked both the probe and the (•)OH scavengers in 37 °C-incubated solutions for 1/2h. The HRS activity was measured using the decrease in CUPRAC absorbance at 450 nm - arising from the reduction of Cu(II)-Nc reagent to the Cu(I)-neocuproine chelate - of the hydroxylated probe (TP) undergoing radical attack in the presence of (•)OH scavengers. The HRS activity was evaluated as the second-order rate constants of biologically active compounds for (•)OH scavenging and also as the percentage scavenging of a measured compound or sample relative to a reference compound. Using this reaction, a kinetic approach was adopted to assess the HRS activity of amino acids, plasma- and thiol-antioxidants. This assay, applicable to small molecule antioxidants and tissue homogenates, proved to be efficient for serine and albumin for which the widely used TBARS (thiobarbituric acid-reactive substances) test is nonresponsive. Under optimal conditions, about half of the probe (TP) was converted into 2-hydroxyterephthalate (hTP), and this monohydroxylated derivative, being the only product of hydroxylation, was a more specific marker of (•)OH than the non-specific malondialdehyde end-product of the TBARS test. The sensor gave a linear response to scavenger concentration in the competition kinetic equation.

  7. Targeted acylation for all the hydroxyls of (+)-catechin and evaluation of their individual contribution to radical scavenging activity.

    PubMed

    Hong, Shan; Liu, Songbai

    2016-04-15

    The reactivity profile of all the hydroxyl groups in (+)-catechin towards acylation and their respective contribution to radical scavenging activity were systematically explored in this work. Selective acylation of the hydroxyls on different rings was carried out employing either a basic or acidic activation strategy. Monoacylation of B ring was achieved effectively with the aid of dimethyltin dichloride. Monoacylation of A ring was accomplished by sequential protection and deprotection of B and C rings. Based on specific acylation of all the individual hydroxyls of (+)-catechins, the structure radical scavenging activity relationship of each hydroxyl of (+)-catechin was established. It was demonstrated that the vicinal phenolic hydroxyls on B ring played the most important role in the ABTS radical scavenging activity and those on A and C rings made a much smaller contribution. This study has laid solid groundwork for further modification of the catechins and improvement of their properties.

  8. Study on the multiple mechanisms underlying the reaction between hydroxyl radical and phenolic compounds by qualitative structure and activity relationship.

    PubMed

    Cheng, Zhiyong; Ren, Jie; Li, Yuanzong; Chang, Wenbao; Chen, Zhida

    2002-12-01

    The activity-structure relationships (ASR) of phenolic compounds as hydroxyl-radical scavengers have mostly been studied and discussed with regard to their iron-chelating and hydrogen-donation properties in Fenton-type system, but extensive elucidation of multiple mechanisms underlying the hydroxyl radical scavenging reaction is out of obtaining up to now. In the present paper, a series of phenolic compounds was studied for their reactivity with hydroxyl radical by computed chemistry and deoxyribose degradation assay. The rate constant (K(S)), an index dependent markedly on the reaction mechanism and intrinsic reactivity of antioxidants, was found to have good correlation with hydroxyl O-H bond strength (DeltaH(f)), electron-donating ability (ionization potential approximated by HOMO energy level), enthalpy of single electron transfer (E(a)), and spin distribution of phenoxyl radicals (Ds(r)) after H-abstraction. Moreover, the theoretical parameters were highly intercorrelated, suggesting that multiple mechanisms co-exist in the hydroxyl-radical-scavenging reaction and interact with each other. Multi-linear regression analysis indicated that, in addition to H-atom transfer, electron transfer process and stability of the resulted phenoxyl radicals also significantly influence the reactivity of quenching hydroxyl radicals. The QSAR model so established here was based on the elucidation of the complex molecular mechanisms, and may reasonably predict the antioxidant activity using simple experimental and calculated parameters.

  9. Detection of hydroxyl radicals during regeneration of granular activated carbon in dielectric barrier discharge plasma system

    NASA Astrophysics Data System (ADS)

    Tang, Shoufeng; Lu, Na; Shang, Kefeng; Li, Jie; Wu, Yan

    2013-03-01

    To understand the reactions taking place in the dielectric barrier discharge (DBD) plasma system of activated carbon regeneration, the determination of active species is necessary. A method based on High Performance Liquid Chromatography with radical trapping by salicylic acid, has been developed to measure hydroxyl radical (•OH) in the DBD plasma reactor. The effects of applied voltage, treatment time, and gas flow rate and atmosphere were investigated. Experimental results indicated that increasing voltage, treatment time and air flow rate could enhance the formation of •OH. Oxygen atmosphere and a suitable GAC water content were contributed to •OH generation. The results give an insight into plasma chemical processes, and can be helpful to optimize the design and application for the plasma system.

  10. Production of Hydroxyl Radical via the Activation of Hydrogen Peroxide by Hydroxylamine.

    PubMed

    Chen, Liwei; Li, Xuchun; Zhang, Jing; Fang, Jingyun; Huang, Yanmin; Wang, Ping; Ma, Jun

    2015-09-01

    The production of the hydroxyl radical (HO·) is important in environmental chemistry. This study reports a new source of HO· generated solely from hydrogen peroxide (H2O2) activated by hydroxylamine (HA). Electron paramagnetic resonance analysis and the oxidation of a HO· probe, benzoic acid, were used to confirm the production of HO·. The production of HO· increased with increasing concentrations of either HA or H2O2 as well as decreasing pH. The second-order rate constant for the reaction was (2.2 ± 0.2) × 10(-4) M(-1) s(-1). HO· was probably produced in two steps: the activation of H2O2 by protonated HA and then reaction between the H2O2 and the intermediate protonated aminoxyl radical generated in the first step. Such a two-step oxidation can possibly be ascribed to the ionizable hydroxyl moiety in the molecular structure of HA, as is suggested by comparing the reactivity of a series of HA derivatives in HO· production. The results shed light on a previously unknown source of HO· formation, which broadens the understanding of its role in environmental processes.

  11. The antimicrobial activity of gramicidin A is associated with hydroxyl radical formation.

    PubMed

    Liou, Je-Wen; Hung, Yu-Jiun; Yang, Chin-Hao; Chen, Yi-Cheng

    2015-01-01

    Gramicidin A is an antimicrobial peptide that destroys gram-positive bacteria. The bactericidal mechanism of antimicrobial peptides has been linked to membrane permeation and metabolism disruption as well as interruption of DNA and protein functions. However, the exact bacterial killing mechanism of gramicidin A is not clearly understood. In the present study, we examined the antimicrobial activity of gramicidin A on Staphylococcus aureus using biochemical and biophysical methods, including hydroxyl radical and NAD+/NADH cycling assays, atomic force microscopy, and Fourier transform infrared spectroscopy. Gramicidin A induced membrane permeabilization and changed the composition of the membrane. The morphology of Staphylococcus aureus during gramicidin A destruction was divided into four stages: pore formation, water permeability, bacterial flattening, and lysis. Changes in membrane composition included the destruction of membrane lipids, proteins, and carbohydrates. Most interestingly, we demonstrated that gramicidin A not only caused membrane permeabilization but also induced the formation of hydroxyl radicals, which are a possible end product of the transient depletion of NADH from the tricarboxylic acid cycle. The latter may be the main cause of complete Staphylococcus aureus killing. This new finding may provide insight into the underlying bactericidal mechanism of gA.

  12. Hydroxyl radical scavengers inhibit lymphocyte mitogenesis.

    PubMed Central

    Novogrodsky, A; Ravid, A; Rubin, A L; Stenzel, K H

    1982-01-01

    Agents that are known to be scavengers of hydroxyl radicals inhibit lymphocyte mitogenesis induced by phorbol myristate acetate (PMA) to a greater extent than they inhibit mitogenesis induced by concanavalin A or phytohemagglutinin. These agents include dimethyl sulfoxide, benzoate, thiourea, dimethylurea, tetramethylurea, L-tryptophan, mannitol, and several other alcohols. Their inhibitory effect is not associated with cytotoxicity. The hydroxyl radical scavengers do not inhibit PMA-dependent amino acid transport in T cells or PMA-induced superoxide production by monocytes. Thus, they do not inhibit the primary interaction of PMA with responding cells. Treatment of peripheral blood mononuclear cells with PMA increased cellular guanylate cyclase in most experiments, and dimethyl sulfoxide tended to inhibit this increase. In addition to inhibition of PMA-induced mitogenesis, hydroxyl radical scavengers markedly inhibited the activity of lymphocyte activating factor (interleukin 1). The differential inhibition of lymphocyte mitogenesis induced by different mitogens appears to be related to the differential macrophage requirements of the mitogens. The data suggest that hydroxyl radicals may be involved in mediating the triggering signal for lymphocyte activation. Some of the hydroxyl radical scavengers are inducers of cellular differentiation,. nd it is possible that their differentiating activity is related to their ability to scavenge free radicals. PMID:6122209

  13. Synthesis, photocatalytic activity, and photogenerated hydroxyl radicals of monodisperse colloidal ZnO nanospheres

    NASA Astrophysics Data System (ADS)

    Yang, Chong; Li, Qingsong; Tang, Limei; Xin, Kun; Bai, Ailing; Yu, Yingmin

    2015-12-01

    In the present study, monodisperse colloidal zinc oxide (ZnO) nanospheres were successfully synthesized via a newly developed two-stage solution method followed by facile calcination at various temperatures. The effects of calcination temperature on the structure, morphology, and optical properties as well as the photocatalytic activity of the as-made ZnO samples were investigated systematically by Fourier transform infrared spectrometry, X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption/desorption isotherms, diffuse reflectance UV-visible spectroscopy (DRS), photoluminescence, and related photocatalytic activity tests. The thermal decomposition was analyzed by thermogravimetric analysis. The crystallinity was found to gradually increase with increasing calcination temperature, whereas the decrease in the Brunauer-Emmett-Teller specific surface area of the samples with calcination may be ascribed to the increased particle size. The DRS results provided clear evidence for the decrease in band gap energy of ZnO samples with an increase in calcination temperature. The photoluminescence spectra demonstrated the calcination-dependent emission features, especially the UV emission intensity. In particular, the ZnO product calcined at 400 °C exhibited the highest photocatalytic activity, degrading methylene blue by almost 99.1% in 70 min, which is ascribed to the large specific surface area and pore volume, high electron-hole pair separation efficient, and great redox potential of the obtained ZnO nanoparticles. In addition, the production of photogenerated hydroxyl radicals (•OH) was consistent with the methylene blue degradation efficiency over the as-made ZnO nanoparticles. Using isopropanol as a hydroxyl radical scavenger, •OH was determined to be the main active oxygen species in the photocatalytic process. A possible mechanism of photodegradation under UV light irradiation also is proposed.

  14. EPR studies on hydroxyl radical-scavenging activities of pravastatin and fluvastatin.

    PubMed

    Vandjelovic, Nathan; Zhu, Hong; Misra, Hara P; Zimmerman, Ryan P; Jia, Zhenquan; Li, Yunbo

    2012-05-01

    Statins are known clinically by their cholesterol reduction properties through the inhibition of HMG-CoA reductase. There is mounting evidence suggesting a protective role of statins in certain types of cancer, cardiac, and vascular disease through a mechanism that extends beyond their lipid lowering ability. The root mechanism of damage likely involves the inflammatory cascade, specifically compounds known as reactive oxygen species such as the hydroxyl radical. However, direct evidence for the hydroxyl-scavenging capacity of pravastatin and fluvastatin, two forms of statins being widely used to lower LDL cholesterol, is still lacking in literature. In this study, electron paramagnetic resonance spectroscopy in combination with 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-spin-trapping technique was utilized to determine the abilities of pravastatin and fluvastatin in scavenging hydroxyl radical generated from Fe(II) with H(2)O(2) system. In addition, we examined the effects of pravastatin and fluvastatin on oxidative-induced φX-174 RF I plasmid DNA damage. We have demonstrated here for the first time that pravastatin and fluvastatin at physiologically relevant concentrations significantly decreased formation of DMPO-OH adduct indicating that both compounds could directly scavenge hydroxyl radicals. However, pravastatin and fluvastatin were not able to directly protect against oxidative DNA plasmid damage. The hydroxyl radical sequestering ability of pravastatin and fluvastatin reported in this study may contribute to their beneficial use in certain types of cancer and in cardiovascular disease.

  15. Oxygen activation at the plasma membrane: relation between superoxide and hydroxyl radical production by isolated membranes.

    PubMed

    Heyno, Eiri; Mary, Véronique; Schopfer, Peter; Krieger-Liszkay, Anja

    2011-07-01

    Production of reactive oxygen species (hydroxyl radicals, superoxide radicals and hydrogen peroxide) was studied using EPR spin-trapping techniques and specific dyes in isolated plasma membranes from the growing and the non-growing zones of hypocotyls and roots of etiolated soybean seedlings as well as coleoptiles and roots of etiolated maize seedlings. NAD(P)H mediated the production of superoxide in all plasma membrane samples. Hydroxyl radicals were only produced by the membranes of the hypocotyl growing zone when a Fenton catalyst (FeEDTA) was present. By contrast, in membranes from other parts of the seedlings a low rate of spontaneous hydroxyl radical formation was observed due to the presence of small amounts of tightly bound peroxidase. It is concluded that apoplastic hydroxyl radical generation depends fully, or for the most part, on peroxidase localized in the cell wall. In soybean plasma membranes from the growing zone of the hypocotyl pharmacological tests showed that the superoxide production could potentially be attributed to the action of at least two enzymes, an NADPH oxidase and, in the presence of menadione, a quinone reductase.

  16. Vibrational Study of Melatonin and its Radioprotective Activity towards Hydroxyl Radical

    NASA Astrophysics Data System (ADS)

    Singh, Gurpreet; Kaur, Sarvpreet; Saini, G. S. S.

    2011-12-01

    Vibrational study of Melatonin (N-acetyl 5-methoxytrypatamin) was done using FTIR and Raman spectroscopy. DFT calculations were employed to the structural analysis of melatonin and to the end products. The theoretical calculations confirmed the different observed vibrational modes. The optimized structure energy calculations of the different end products confirmed the most probable site of the hydroxyl radical attack is the hydrogen attached to nitrogen present in the indole ring.

  17. Formation of hydroxyl radicals contributes to the bactericidal activity of ciprofloxacin against Pseudomonas aeruginosa biofilms.

    PubMed

    Jensen, Peter Ø; Briales, Alejandra; Brochmann, Rikke P; Wang, Hengzhuang; Kragh, Kasper N; Kolpen, Mette; Hempel, Casper; Bjarnsholt, Thomas; Høiby, Niels; Ciofu, Oana

    2014-04-01

    Antibiotic-tolerant, biofilm-forming Pseudomonas aeruginosa has long been recognized as a major cause of chronic lung infections of cystic fibrosis patients. The mechanisms involved in the activity of antibiotics on biofilm are not completely clear. We have investigated whether the proposed induction of cytotoxic hydroxyl radicals (OH˙) during antibiotic treatment of planktonically grown cells may contribute to action of the commonly used antibiotic ciprofloxacin on P. aeruginosa biofilms. For this purpose, WT PAO1, a catalase deficient ΔkatA and a ciprofloxacin resistant mutant of PAO1 (gyrA), were grown as biofilms in microtiter plates and treated with ciprofloxacin. Formation of OH˙ and total amount of reactive oxygen species (ROS) was measured and viability was estimated. Formation of OH˙ and total ROS in PAO1 biofilms treated with ciprofloxacin was shown but higher levels were measured in ΔkatA biofilms, and no ROS production was seen in the gyrA biofilms. Treatment with ciprofloxacin decreased the viability of PAO1 and ΔkatA biofilms but not of gyrA biofilms. Addition of thiourea, a OH˙ scavenger, decreased the OH˙ levels and killing of PAO1 biofilm. Our study shows that OH˙ is produced by P. aeruginosa biofilms treated with ciprofloxacin, which may contribute to the killing of biofilm subpopulations.

  18. New insights into the aquatic photochemistry of fluoroquinolone antibiotics: Direct photodegradation, hydroxyl-radical oxidation, and antibacterial activity changes.

    PubMed

    Ge, Linke; Na, Guangshui; Zhang, Siyu; Li, Kai; Zhang, Peng; Ren, Honglei; Yao, Ziwei

    2015-09-15

    The ubiquity and photoreactivity of fluoroquinolone antibiotics (FQs) in surface waters urge new insights into their aqueous photochemical behavior. This study concerns the photochemistry of 6 FQs: ciprofloxacin, danofloxacin, levofloxacin, sarafloxacin, difloxacin and enrofloxacin. Methods were developed to calculate their solar direct photodegradation half-lives (td,E) and hydroxyl-radical oxidation half-lives (tOH,E) in sunlit surface waters. The td,E values range from 0.56 min to 28.8 min at 45° N latitude, whereas tOH,E ranges from 3.24h to 33.6h, suggesting that most FQs tend to undergo fast direct photolysis rather than hydroxyl-radical oxidation in surface waters. However, a case study for levofloxacin and sarafloxacin indicated that the hydroxyl-radical oxidation induced risky photochlorination and resulted in multi-degradation pathways, such as piperazinyl hydroxylation and clearage. Changes in the antibacterial activity of FQs caused by photodegradation in various waters were further examined using Escherichia coli, and it was found that the activity evolution depended on primary photodegradation pathways and products. Primary intermediates with intact FQ nuclei retained significant antibacterial activity. These results are important for assessing the fate and risk of FQs in surface waters.

  19. Optimization of hydroxyl radical scavenging activity of exo-polysaccharides from Inonotus obliquus in submerged fermentation using response surface methodology.

    PubMed

    Chen, Hui; Xu, Xiangqun; Zhu, Yang

    2010-04-01

    The objectives of this study were to investigate the effect of fermentation medium on the hydroxyl radical scavenging activity of exo-polysaccharides from Inonotus obliquus by response surface methodology. A two-level fractional factorial design was used to evaluate the effect of different components of medium. Corn flour, peptone, and KH2PO4 were important factors significantly affecting hydroxyl radical scavenging activity. These selected variables were subsequently optimized using path of steepest ascent (descent), a central composite design, and response surface analysis. The optimal medium composition was (% w/v): corn flour 5.30, peptone 0.32, KH2PO4 0.26, MgSO4 0.02, and CaCl2 0.01. Under the optimal condition, the hydroxyl radical scavenging rate (49.4%) was much higher than that using either basal fermentation medium (10.2%) and single variable optimization of fermentation medium (35.5%). The main monosaccharides components of the RSM optimized polysaccharides are rhamnose, arabinose, xylose, mannose, glucose and galactose with molar proportion at 1.45%, 3.63%, 2.17%, 15.94%, 50.00%, and 26.81%.

  20. Dual-emissive fluorescence measurements of hydroxyl radicals using a coumarin-activated silica nanohybrid probe.

    PubMed

    Liu, Saisai; Zhao, Jun; Zhang, Kui; Yang, Lei; Sun, Mingtai; Yu, Huan; Yan, Yehan; Zhang, Yajun; Wu, Lijun; Wang, Suhua

    2016-04-07

    This work reports a novel dual-emissive fluorescent probe based on dye hybrid silica nanoparticles for ratiometric measurement of the hydroxyl radical (˙OH). In the probe sensing system, the blue emission of coumarin dye (coumarin-3-carboxylic acid, CCA) immobilized on the nanoparticle surface is selectively enhanced by ˙OH due to the formation of a coumarin hydroxylation product with strong fluorescence, whereas the emission of red fluorescent dye encapsulated in the silica nanoparticle is insensitive to ˙OH as a self-referencing signal, and so the probe provides a good quantitative analysis based on ratiometric fluorescence measurement with a detection limit of 1.65 μM. Moreover, the probe also shows high selectivity for ˙OH determination against metal ions, other reactive oxygen species and biological species. More importantly, it exhibits low cytotoxicity and high biocompatibility in living cells, and has been successfully used for cellular imaging of ˙OH, showing its promising application for monitoring of intracellular ˙OH signaling events.

  1. Photoinduced hydroxyl radical and photocatalytic activity of samarium-doped TiO(2) nanocrystalline.

    PubMed

    Xiao, Qi; Si, Zhichun; Zhang, Jiang; Xiao, Chong; Tan, Xiaoke

    2008-01-15

    Sm(3+)-doped TiO(2) nanocrystalline has been prepared by sol-gel auto-combustion technique and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and also UV-vis diffuse reflectance spectroscopy (DRS). These Sm(3+)-doped TiO(2) samples were tested for methylene blue (MB) decomposition and *OH radical formation. The analysis of *OH radical formation on the sample surface under UV irradiation was performed by fluorescence technique with using terephthalic acid, which readily reacted with *OH radical to produce highly fluorescent product, 2-hydroxyterephthalic acid. It was observed that the presence of Sm(3+) ion as a dopant significantly enhanced the photocatalytic activity for MB degradation under UV light irradiation because both the larger specific surface area and the greater the formation rate of *OH radical were simultaneously obtained for Sm(3+)-doped TiO(2) nanocrystalline. The adsorption experimental demonstrated that Sm(3+)-TiO(2) had a higher MB adsorption capacity than undoped TiO(2) and the adsorption capacity of MB increased with the increase of samarium ion content. The results also indicated that the greater the formation rate of *OH radical was, the higher photocatalytic activity was achieved. In this study, the optimum amount of Sm(3+) doping was 0.5 mol%, at which the recombination of photo-induced electrons and holes could be effectively inhibited, the highest formation rate of *OH radicals was, and thereby the highest photocatalytic activity was achieved.

  2. Quantitative structure-activity relationship of hydroxyl-substituent Schiff bases in radical-induced hemolysis of human erythrocytes.

    PubMed

    Tang, You-Zhi; Liu, Zai-Qun

    2008-01-01

    The major objective of this work was to explore the quantitative structure-activity relationship (QSAR) of hydroxyl-substituent Schiff bases in protecting human erythrocytes against 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)- induced hemolysis, in which 10 Schiff bases including 4-phenyliminomethylphenol (PIH); 4-((4-hydroxybenzylidene) amino)phenol (PAH); 2-methoxy-4-((4-hydroxyphenylimino)methyl)phenol (PMH); 4-((furan-2-ylmethylene)amino) phenol (FAH); 4-((4-N,N-dimethylaminobenzylidene)amino)phenol (PDH); 2-((4-N,N-dimethylaminobenzylidene)amino) phenol (ODH); 2-(naphthalene-1-yliminomethyl)phenol (NAH); 2-(benzyliminomethyl)phenol (BPH); 1,4-di((2-hydroxyphenylimino) methyl)benzene (DOH); 1,4-di((4-hydroxyphenylimino)methyl)benzene DPH, were available for this in vitro experimental system. The results revealed that the radical-scavenging activity of the --OH attached to the para position of methylene in Schiff base was much lower than that attached to the ortho position of the N atom. The large conjugate system and low steric hindrance in the framework of Schiff base benefit the Schiff base to trap radicals. Meanwhile, since a Schiff base, even without any substituent, can also play an antioxidative role in this experimental system, the QSAR results suggest that hydroxyl-substituent Schiff bases are potential drugs in the treatment of radical-related diseases, and provide more information for designing novel drugs.

  3. Superoxide dismutase activity of the naturally occurring human serum albumin-copper complex without hydroxyl radical formation.

    PubMed

    Kato, Ryunosuke; Akiyama, Matofusa; Kawakami, Hiroyoshi; Komatsu, Teruyuki

    2014-01-01

    The superoxide radical anion (O2(.-)) is biologically toxic and contributes to the pathogenesis of various diseases. Here we describe the superoxide dismutase (SOD) activity of human serum albumin (HSA) complexed with a single Cu(II) ion at the N-terminal end (HSA-Cu complex). The structure of this naturally occurring copper-coordinated blood serum protein has been characterized by several physicochemical measurements. The O2(.-) dismutation ability of the HSA-Cu (1:1) complex is almost the same as that of the well-known SOD mimics, such as Mn(III) -tetrakis(N-methylpyridinium)porphyrin. Interestingly, the HSA-Cu complex does not induce a subsequent Fenton reaction to produce the hydroxyl radical (OH(.)), which is one of the most harmful reactive oxygen species.

  4. Antioxidant activity of the giant jellyfish Nemopilema nomurai measured by the oxygen radical absorbance capacity and hydroxyl radical averting capacity methods.

    PubMed

    Harada, Kazuki; Maeda, Toshimichi; Hasegawa, Yoshiro; Tokunaga, Takushi; Ogawa, Shinya; Fukuda, Kyoko; Nagatsuka, Norie; Nagao, Keiko; Ueno, Shunshiro

    2011-01-01

    The giant jellyfish Nemopilema nomurai (reaching sizes of up to 2 m diameter and 150 kg), which forms dense blooms, has caused extensive damage to fisheries by overloading trawl nets, while its toxic nematocysts cause dermatological symptoms. Giant jellyfish are currently discarded on the grounds of pest control. However, the giant jellyfish is considered to be edible and is part of Chinese cuisine. Therefore, we investigated whether any benefits for human health may be derived from consumption of the jellyfish in order to formulate medicated diets. Antioxidant activity of Nemopilema nomurai was measured using the oxygen radical absorbance capacity (ORAC) and hydroxyl radical averting capacity (HORAC) methods. Based on the results, the ORAC value of the giant jellyfish freeze-dried sample was 541 µmol trolox equivalent (TE)/100 g and the HORAC value was 3,687 µmol gallic acid equivalent (GAE)/100 g. On the other hand, the IC50 value of hydroxyl radical scavenging activity measured by using the electron spin resonance method was 3.3%. In conclusion, the results suggest that the freeze-dried powder of the giant jellyfish Nemopilema nomurai is a potentially beneficial food for humans.

  5. The hydroxyl radical in plants: from seed to seed.

    PubMed

    Richards, Siân L; Wilkins, Katie A; Swarbreck, Stéphanie M; Anderson, Alexander A; Habib, Noman; Smith, Alison G; McAinsh, Martin; Davies, Julia M

    2015-01-01

    The hydroxyl radical (OH(•)) is the most potent yet short-lived of the reactive oxygen species (ROS) radicals. Just as hydrogen peroxide was once considered to be simply a deleterious by-product of oxidative metabolism but is now acknowledged to have signalling roles in plant cells, so evidence is mounting for the hydroxyl radical as being more than merely an agent of destruction. Its oxidative power is harnessed to facilitate germination, growth, stomatal closure, reproduction, the immune response, and adaptation to stress. It features in plant cell death and is a key tool in microbial degradation of plant matter for recycling. Production of the hydroxyl radical in the wall, at the plasma membrane, and intracellularly is facilitated by a range of peroxidases, superoxide dismutases, NADPH oxidases, and transition metal catalysts. The spatio-temporal activity of these must be tightly regulated to target substrates precisely to the site of radical production, both to prevent damage and to accommodate the short half life and diffusive capacity of the hydroxyl radical. Whilst research has focussed mainly on the hydroxyl radical's mode of action in wall loosening, studies now extend to elucidating which proteins are targets in signalling systems. Despite the difficulties in detecting and manipulating this ROS, there is sufficient evidence now to acknowledge the hydroxyl radical as a potent regulator in plant cell biology.

  6. Hydroxyl radical oxidation of feruloylated arabinoxylan.

    PubMed

    Bagdi, Attila; Tömösközi, Sándor; Nyström, Laura

    2016-11-05

    Feruloylated arabinoxylan (AX) has a unique capacity to form covalent gels in the presence of certain oxidizing agents. The present study demonstrates that hydroxyl radical oxidation does not provoke ferulic acid dimerization and thus oxidative gelation. We studied the hydroxyl radical mediated oxidation of an alkali-extracted AX preparation (purity: 92g/100g dry matter) that showed gel-forming capability upon peroxidase/hydrogen peroxide treatment. Hydroxyl radicals were produced with ascorbate-driven Fenton reaction and the radical formation was monitored with electron paramagnetic resonance, using a POBN/EtOH spin trapping system. Oxidation was carried out at different catalytic concentrations of iron (50 and 100μM) and at different temperatures (20°C, 50°C, and 80°C). It was demonstrated that hydroxyl radical oxidation does not provoke gel formation, but viscosity decrease in AX solution, which suggests polymer degradation. Furthermore, it was demonstrated that hydroxyl radical formation in AX solution can be initiated merely by increasing temperature.

  7. Effect of Curcumin Against Oxidation of Biomolecules by Hydroxyl Radicals

    PubMed Central

    Mahendra, Jaideep; Gurumurthy, Prema; Jayamathi; Iqbal, Shabeer S; Mahendra, Little

    2014-01-01

    Background: Among various reactive oxygen species, hydroxyl radicals have the strongest chemical activity, which can damage a wide range of essential biomolecules such as lipids, proteins, and DNA. Objective: The objective of this study was to investigate the beneficial effects of curcumin on prevention of oxidative damage of biomolecules by hydroxyl radicals generated in in vitro by a Fenton like reaction. Materials and Methods: We have incubated the serum, plasma and whole blood with H2O2/Cu2+/ Ascorbic acid system for 4 hours at 37 0C and observed the oxidation of biomolecules like albumin, lipids, proteins and DNA. Results: Curcumin at the concentrations of 50,100 and 200 μmoles, prevented the formation of ischemia modified albumin, MDA, protein carbonyls, oxidized DNA and increased the total antioxidant levels and GSH significantly. Conclusion: These observations suggest the hydroxyl radical scavenging potentials of curcumin and protective actions to prevent the oxidation of biomolecules by hydroxyl radicals. PMID:25478334

  8. Radical-scavenging activities of new hydroxylated ursane triterpenes from cv. Annurca apples.

    PubMed

    D'Abrosca, Brigida; Fiorentino, Antonio; Monaco, Pietro; Pacifico, Severina

    2005-07-01

    Two new ursolic acid triterpene derivatives, compounds 2 and 3, have been isolated from cv. Annurca apple fruit, a high-quality apple variety widely cultivated in southern Italy, together with the known 2-oxopomolic acid (1). The new compounds were identified by means of different spectroscopic techniques as 3-epi-2-oxopomolic acid (= (3alpha)-3,19-dihydroxy-2-oxours-12-en-28-oic acid; 2) and (1alpha)-1-hydroxy-3-oxours-12-en-28-oic acid (3). Compounds 1-3 were tested for their radical-scavenging activities with the aid of a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay (Fig. 2). All three constituents showed activities similar to that of the reference antioxidant alpha-tocopherol (vitamin E).

  9. Degradation of pentachlorophenol by hydroxyl radicals and sulfate radicals using electrochemical activation of peroxomonosulfate, peroxodisulfate and hydrogen peroxide.

    PubMed

    Govindan, Kadarkarai; Raja, Mohan; Noel, Michael; James, E J

    2014-05-15

    The present study is to investigate the reactivity of free radicals (SO4(-) and HO) generated from common oxidants (peroxomonosulfate (PMS), peroxodisulfate (PDS) and hydrogen peroxide (HP)) activated by electrochemically generated Fe(2+)/Fe(3+) ions which furthermore are evaluated to destroy pentachlorophenol (PCP) in aqueous solution. The effect of solution pH and amount of oxidants (PMS, PDS and HP) in electrocoagulation (EC) on PCP degradation is analyzed in detail. The experimental results reveal that, optimum initial solution pH is 4.5 and PMS is more efficient oxidant addition in EC. 75% PCP degradation is achieved at 60min electrolysis time from PMS assisted EC. According to the first order rate constant, faster PCP degradation rate is obtained by PMS assisted EC. The PCP degradation rate by oxidant assisted EC is observed in the following order: EC/PMS>EC/PDS>EC/HP>EC. Further to identify the influences of experimental factors involved in PCP degradation by oxidant assisted EC, an experimental design based on an orthogonal array (OA) L9 (3(3)) is proposed using Taguchi method. The factors that most significantly affect the process robustness are identified as A (oxidant) and B (pH) which together account for nearly 86% of the variance.

  10. A comparative study of the hydroxyl radical scavenging capacity of activated sludge and membrane bioreactor wastewater effluents.

    PubMed

    Grant, Jacque-Ann; Hofmann, Ron

    2016-01-01

    This study evaluated the hydroxyl radical scavenging characteristics of wastewater from five membrane bioreactor (MBR) and five activated sludge (AS) systems. The average values of the characteristics of both wastewater types was found to be significantly different at a 90% confidence interval in terms UV absorbance at 254 nm, alkalinity, and biopolymer concentration. Effluent organic matter (EfOM), with an average kOH,EfOM of (2.75 ± 1.04) × 10(8) M(-1)s(-1), was identified as the primary hydroxyl scavenger contributing to >70% of the background scavenging in all cases, except when nitrite exceeded 0.3 mg NO(2)(-)-N/L. The average scavenging capacity, EfOM scavenging capacity, and the EfOM reaction rate constant of the AS wastewaters exceeded that of the MBR. However, due to the small sample size (n = 5) and considerable variability in scavenging characteristics among the MBR wastewaters, the difference in EfOM reactivity between the two wastewaters was not statistically significant at a 90% confidence interval. Nevertheless, these preliminary findings suggest the possibility that MBR wastewaters may be more amenable to treatment by advanced oxidation. A plausible explanation is that MBRs were observed to reject biopolymers, and a strong correlation was observed between EfOM scavenging capacity and biopolymer concentration.

  11. Hydroxyl radical generation by red tide algae.

    PubMed

    Oda, T; Akaike, T; Sato, K; Ishimatsu, A; Takeshita, S; Muramatsu, T; Maeda, H

    1992-04-01

    The unicellular marine phytoplankton Chattonella marina is known to have toxic effects against various living marine organisms, especially fishes. However, details of the mechanism of the toxicity of this plankton remain obscure. Here we demonstrate the generation of superoxide and hydroxyl radicals from a red tide unicellular organism, C. marina, by using ESR spectroscopy with the spin traps 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and N-t-butyl-alpha-phenylnitrone (PBN), and by using the luminol-enhanced chemiluminescence response. The spin-trapping assay revealed productions of spin adduct of superoxide anion (O2-) (DMPO-OOH) and that of hydroxyl radical (.OH) (DMPO-OH) in the algal suspension, which was not observed in the ultrasonic-ruptured suspension. The addition of superoxide dismutase (500 U/ml) almost completely inhibited the formation of both DMPO-OOH and DMPO-OH, and carbon-centered radicals were generated with the disappearance of DMPO-OH after addition of 5% dimethyl sulfoxide (Me2SO) and 5% ethanol. Furthermore, the generation of methyl and methoxyl radicals, which are thought to be produced by the reaction of hydroxyl radical and Me2SO under aerobic condition, was identified using spin trapping with a combination of PBN and Me2SO. Luminol-enhanced chemiluminescence assay also supported the above observations. These results clearly indicate that C. marina generates and releases the superoxide radical followed by the production of hydroxyl radical to the surrounding environment. The velocity of superoxide generation by C. marina was about 100 times faster than that by mammalian phagocytes per cell basis. The generation of oxygen radical is suggested to be a pathogenic principle in the toxication of red tide to susceptible aquaculture fishes and may be directly correlated with the coastal pollution by red tide.

  12. Lethal hydroxyl radical accumulation by a lactococcal bacteriocin, lacticin Q.

    PubMed

    Li, Mengqi; Yoneyama, Fuminori; Toshimitsu, Nayu; Zendo, Takeshi; Nakayama, Jiro; Sonomoto, Kenji

    2013-08-01

    The antimicrobial mechanism of a lactococcal bacteriocin, lacticin Q, can be described by the toroidal pore model without any receptor. However, lacticin Q showed different degrees of activity (selective antimicrobial activity) against Gram-positive bacteria even among related species. The ability of lacticin Q to induce pore formation in liposomes composed of lipids from different indicator strains indicated that its selective antimicrobial activity could not be attributed only to membrane lipid composition. We investigated the accumulation of deleterious hydroxyl radicals after exposure to lacticin Q as a contributing factor to cell death in the indicator strains. When lacticin Q of the same concentration as the MIC or minimum bactericidal concentration was added to the indicator cultures, high levels of hydroxyl radical accumulation were detected. Treatment with hydroxyl radical scavengers, thiourea and 2,2'-bipyridyl, decreased the levels of hydroxyl radical accumulation and recovered cell viability. These results suggest that, with or without pore formation, the final antimicrobial mechanism of lacticin Q is the accumulation of hydroxyl radicals, which varies by strain, resulting in the selective antimicrobial activity of lacticin Q.

  13. Lethal Hydroxyl Radical Accumulation by a Lactococcal Bacteriocin, Lacticin Q

    PubMed Central

    Li, Mengqi; Yoneyama, Fuminori; Toshimitsu, Nayu; Zendo, Takeshi; Nakayama, Jiro

    2013-01-01

    The antimicrobial mechanism of a lactococcal bacteriocin, lacticin Q, can be described by the toroidal pore model without any receptor. However, lacticin Q showed different degrees of activity (selective antimicrobial activity) against Gram-positive bacteria even among related species. The ability of lacticin Q to induce pore formation in liposomes composed of lipids from different indicator strains indicated that its selective antimicrobial activity could not be attributed only to membrane lipid composition. We investigated the accumulation of deleterious hydroxyl radicals after exposure to lacticin Q as a contributing factor to cell death in the indicator strains. When lacticin Q of the same concentration as the MIC or minimum bactericidal concentration was added to the indicator cultures, high levels of hydroxyl radical accumulation were detected. Treatment with hydroxyl radical scavengers, thiourea and 2,2′-bipyridyl, decreased the levels of hydroxyl radical accumulation and recovered cell viability. These results suggest that, with or without pore formation, the final antimicrobial mechanism of lacticin Q is the accumulation of hydroxyl radicals, which varies by strain, resulting in the selective antimicrobial activity of lacticin Q. PMID:23733459

  14. MEASUREMENT OF HYDROXYL RADICAL ACTIVITY IN A SOIL SLURRY USING THE SPIN TRAP A-(4-PYRIDYL-1-OXIDE)-N-TERT-BUTYLNITRONE

    EPA Science Inventory

    The spin trap compound a-(4-pyridyl-1-oxide)N-tert-butylnitrone (4-POBN) served as a probe to estimate the activity of Fenton-derived hydroxyl radicals (.OH) in a batch suspension comprised of silica sand and crushes goethite ore. The rate of probe disappearance was used to anal...

  15. Novel hydroxyl radical scavenging antioxidant activity assay for water-soluble antioxidants using a modified CUPRAC method.

    PubMed

    Bektaşoğlu, Burcu; Esin Celik, Saliha; Ozyürek, Mustafa; Güçlü, Kubilay; Apak, Reşat

    2006-07-07

    Reactive oxygen species (ROS) such as superoxide anion, hydroxyl ((*)OH), peroxyl, and alkoxyl radicals may attack biological macromolecules giving rise to oxidative stress-originated diseases. Since (*)OH is very short-lived, secondary products resulting from (*)OH attack to various probes are measured. Although the measurement of aromatic hydroxylation with HPLC/electrochemical detection is more specific than the low-yield TBARS test, it requires sophisticated instrumentation. As a more convenient and less costly alternative, we used p-aminobenzoate, 2,4- and 3,5-dimethoxybenzoate probes for detecting hydroxyl radicals generated from an equivalent mixture of Fe(II)+EDTA with hydrogen peroxide. The produced hydroxyl radicals attacked both the probe and the water-soluble antioxidants in 37 degrees C-incubated solutions for 2h. The CUPRAC (i.e., our original method for total antioxidant capacity assay) absorbance of the ethylacetate extract due to the reduction of Cu(II)-neocuproine reagent by the hydroxylated probe decreased in the presence of (*)OH scavengers, the difference being proportional to the scavenging ability of the tested compound. A rate constant for the reaction of the scavenger with hydroxyl radical can be deduced from the inhibition of color formation. The second-order rate constants of the scavengers were determined with competition kinetics by means of a linear plot of A(0)/A as a function of C(scavenger)/C(probe), where A(0) and A are the CUPRAC absorbances of the system in the absence and presence of scavenger, respectively, and C is the molar concentration of relevant species. The 2,4- and 3,5-dimethoxybenzoates were the best probes in terms of linearity and sensitivity. Iodide, metabisulfite, hexacyanoferrate(II), thiourea, formate, and dimethyl sulfoxide were shown by the modified CUPRAC assay to be more effective scavengers than mannitol, glucose, lysine, and simple alcohols, as in the TBARS assay. The developed method is less lengthy, more

  16. The iron complex of Dp44mT is redox-active and induces hydroxyl radical formation: an EPR study.

    PubMed

    Jansson, Patric J; Hawkins, Clare L; Lovejoy, David B; Richardson, Des R

    2010-11-01

    Iron chelation therapy was initially designed to alleviate the toxic effects of excess iron evident in iron-overload diseases. However, some iron chelator-metal complexes have also gained interest due to their high redox activity and toxicological properties that have potential for cancer chemotherapy. This communication addresses the conflicting results published recently on the ability of the iron chelator, Dp44mT, to induce hydroxyl radical formation upon complexation with iron (B.B. Hasinoff and D. Patel, J Inorg. Biochem.103 (2009), 1093-1101). This previous study used EPR spin-trapping to show that Dp44mT-iron complexes were not able to generate hydroxyl radicals. Here, we demonstrate the opposite by using the same technique under very similar conditions to show the Dp44mT-iron complex is indeed redox-active and induces hydroxyl radical formation. This was studied directly in an iron(II)/H(2)O(2) reaction system or using a reducing iron(III)/ascorbate system implementing several different buffers at pH 7.4. The demonstration by EPR that the Dp44mT-iron complex is redox-active confirms our previous studies using cyclic voltammetry, ascorbate oxidation, benzoate hydroxylation and a plasmid DNA strand-break assay. We discuss the relevance of the redox activity to the biological effects of Dp44mT.

  17. Rate Constants and Activation Energies for Gas‐Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical

    PubMed Central

    Safron, Andreas; Strandell, Michael; Kierkegaard, Amelie

    2015-01-01

    ABSTRACT Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second‐order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140‐mL gas‐phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D4 and D5 with the OH radical are 1.9 × 10−12 (95% confidence interval (CI): (1.7–2.2) × 10−12) and 2.6 × 10−12 (CI: (2.3–2.9) × 10−12) cm3 molecule−1 s−1, respectively, which are 1.9× and 1.7× faster than previous measurements. Our measured rate constant for D6 is 2.8 × 10−12 (CI: (2.5–3.2) × 10−12) cm3 molecule−1 s−1 and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D5 were 33% higher than for D4 (CI: 30–37%), whereas the rates for D6 were only 8% higher than for D5 (CI: 5–10%). The activation energies of the reactions of D4, D5, and D6 with OH were not statistically different and had a value of 4300 ± 2800 J/mol. PMID:27708500

  18. Rate Constants and Activation Energies for Gas-Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical.

    PubMed

    Safron, Andreas; Strandell, Michael; Kierkegaard, Amelie; Macleod, Matthew

    2015-07-01

    Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second-order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140-mL gas-phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D4 and D5 with the OH radical are 1.9 × 10(-12) (95% confidence interval (CI): (1.7-2.2) × 10(-12)) and 2.6 × 10(-12) (CI: (2.3-2.9) × 10(-12)) cm(3) molecule(-1) s(-1), respectively, which are 1.9× and 1.7× faster than previous measurements. Our measured rate constant for D6 is 2.8 × 10(-12) (CI: (2.5-3.2) × 10(-12)) cm(3) molecule(-1) s(-1) and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D5 were 33% higher than for D4 (CI: 30-37%), whereas the rates for D6 were only 8% higher than for D5 (CI: 5-10%). The activation energies of the reactions of D4, D5, and D6 with OH were not statistically different and had a value of 4300 ± 2800 J/mol.

  19. DNA binding, antitumor activities, and hydroxyl radical scavenging properties of novel oxovanadium (IV) complexes with substituted isoniazid.

    PubMed

    Liao, Xiangwen; Lu, Jiazheng; Ying, Peng; Zhao, Ping; Bai, Yinliang; Li, Wengjie; Liu, Mingpei

    2013-12-01

    Four novel oxovanadium(IV) complexes—[VO(PAHN)(phen)] (1; PAHN is 4-pyridinecarboxylic acid, 2-[(2-hydroxy)-1-naphthalenylene] hydrazide, phen is 1,10-phenanthroline), [VO(PAHN)(bpy)] (2; bpy is 2,2′-bipyridine), [VO(PAH)(phen)] (3; PAH is 4-pyridinecarboxylic acid, 2-[(2-hydroxy)-1-phenyl]methylene hydrazide), and [VO(PAH)(bpy)] (4)—have been synthesized and characterized by elemental analysis, UV–vis spectroscopy, electrospray ionization mass spectrometry, IR spectroscopy, 1H-NMR spectroscopy, and 13C-NMR spectroscopy. Their interactions with calf thymus DNA were investigated. The results suggest that these complexes bind to DNA in an intercalative mode. All four complexes exhibited highly cytotoxic activity against tumor cells (SH-SY5Y, MCF-7, and SK-N-SH), with 50 % inhibitory concentrations of the same order of magnitude as for cisplatin or of lower order of magnitude. Complex 1 exhibited the highest interaction ability and was found to be the most potent antitumor agent among the four complexes. It can cause G2/M phase arrest of the cell cycle, induces significant apoptosis in SK-N-SH cells, and displays typical morphological apoptotic characteristics. In addition, their hydroxyl radical scavenging properties have been tested, and complex 1 was the best inhibitor.

  20. Probing RNA folding by hydroxyl radical footprinting.

    PubMed

    Costa, Maria; Monachello, Dario

    2014-01-01

    In recent years RNA molecules have emerged as central players in the regulation of gene expression. Many of these noncoding RNAs possess well-defined, complex, three-dimensional structures which are essential for their biological function. In this context, much effort has been devoted to develop computational and experimental techniques for RNA structure determination. Among available experimental tools to investigate the higher-order folding of structured RNAs, hydroxyl radical probing stands as one of the most informative and reliable ones. Hydroxyl radicals are oxidative species that cleave the nucleic acid backbone solely according to the solvent accessibility of individual phosphodiester bonds, with no sequence or secondary structure specificity. Therefore, the cleavage pattern obtained directly reflects the degree of protection/exposure to the solvent of each section of the molecule under inspection, providing valuable information about how these different sections interact together to form the final three-dimensional architecture. In this chapter we describe a robust, accurate and very sensitive hydroxyl radical probing method that can be applied to any structured RNA molecule and is suitable to investigate RNA folding and RNA conformational changes induced by binding of a ligand.

  1. Evidence for hydroxyl radical generation during lipid (linoleate) peroxidation.

    PubMed

    Frenette, Mathieu; Scaiano, Juan C

    2008-07-30

    The autoxidation of methyl linoleate in benzene at 37 degrees C by peroxyl radicals was found to generate hydroxyl radicals (.OH) from a secondary oxidation mechanism. The yield of hydroxyl radicals (approximately 2%) was determined by trapping these reactive radicals with benzene to give phenol. We propose that alphaC-H hydrogen abstraction from lipid hydroperoxides, the main autoxidation products, is the source of hydroxyl radicals.

  2. Manganese complexes of curcumin analogues: evaluation of hydroxyl radical scavenging ability, superoxide dismutase activity and stability towards hydrolysis.

    PubMed

    Vajragupta, Opa; Boonchoong, Preecha; Berliner, Lawrence J

    2004-03-01

    In order to improve the antioxidant property of curcumin and its analogue, diacetylcurcumin, manganese was incorporated into the structures in order to enhance superoxide dismutase (SOD) activity. Manganese (Mn) complexes of curcumin (CpCpx) and diacetylcurcumin (AcylCpCpx) were synthesized and firstly investigated for SOD activity and hydroxyl radical (HO*) scavenging ability. SOD activity was evaluated by both the nitroblue tetrazolium (NBT) reduction assay and electron paramagnetic resonance (EPR) with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trapping agent. CpCpx and AcylCpCpx inhibited the NBT reduction and decreased the DMPO/OOH adduct much greater than corresponding antioxidants or ligands, with IC50 values of 29.9 and 24.7 microM (NBT), and 1.09 and 2.40 mM (EPR), respectively. For EPR, potassium superoxide (KO2) was used as a source of O2- where qualitative results suggested that CpCpx and AcylCpCpx were SOD mimics, which catalyze the conversion of O2- to dioxygen and hydrogen peroxide (H2O2). Additionally, CpCpx and AcylCpCpx exhibited the great inhibition of DMPO/OH adduct formation with an IC50 of 0.57 and 0.37mM, respectively, which were comparable to that of curcumin (IC50 of 0.64 mM), indicating that both Mn complexes are also an effective HO* scavenger. The stability against hydrolysis in water, various buffers and human blood/serum was carried out in vitro. It was found that both Mn complexes were pH and salt concentration dependent, being more stable in basic pH. In the human blood/serum test, CpCpx was more stable against hydrolysis than AcylCpCpx with about 10 and 20% of free Mn2+ releasing, respectively.

  3. Oxidation of ambient biogenic secondary organic aerosol by hydroxyl radicals: Effects on cloud condensation nuclei activity

    NASA Astrophysics Data System (ADS)

    Wong, J. P. S.; Lee, A. K. Y.; Slowik, J. G.; Cziczo, D. J.; Leaitch, W. R.; Macdonald, A.; Abbatt, J. P. D.

    2011-11-01

    Changes in the hygroscopicity of ambient biogenic secondary organic aerosols (SOA) due to controlled OH oxidation were investigated at a remote forested site at Whistler Mountain, British Columbia during July of 2010. Coupled photo-oxidation and cloud condensation nuclei (CCN) experiments were conducted on: i) ambient particles exposed to high levels of gas-phase OH, and ii) the water-soluble fraction of ambient particles oxidized by aqueous-phase OH. An Aerodyne Aerosol Mass Spectrometer (AMS) monitored the changes in the chemical composition and degree of oxidation (O:C ratio) of the organic component of ambient aerosol due to OH oxidation. The CCN activity of size-selected particles was measured to determine the hygroscopicity parameter ($\\kappa$org,CCN) for particles of various degrees of oxygenation. In both cases, the CCN activity of the oxidized material was higher than that of the ambient particles. In general, $\\kappa$org,CCN of the aerosol increases with its O:C ratio, in agreement with previous laboratory measurements.

  4. Bismuth increases hydroxyl radical-scavenging activity of histamine H2-receptor antagonists.

    PubMed

    Kirkova, Margarita; Alexandrova, Albena; Yordanova, Neli

    2006-01-01

    The effects of histamine H2-receptor antagonists, alone or in a combination with bismuth, on *OH-provoked degradation of deoxyribose were studied. The histamine H2-receptor antagonists (cimetidine, ranitidine and roxatidine), themselves decreased the deoxyribose damage in Fenton-type systems. In combinations with bismuth, their inhibitory effect in Fenton system (Fe(III)/ascorbic acid + H2O2 was stronger. Moreover, unlike F(III) and Cu(II), which in the presence of ascorbic acid + H2O2 led to an increase in the *OH formation (deoxyribose damage), Bi(III) showed an opposite effect. The present results are interpreted in view of a better ( )OH scavenging activity of bismuth complexes of histamine H2-receptor antagonists as compared to that of the corresponding drugs. These findings might be one more explanation why bismuth salts, in combination with acid-reducing agents, are more effective anti-ulcer agents.

  5. In situ generation of a hydroxyl radical by nanoporous activated carbon derived from rice husk for environmental applications: kinetic and thermodynamic constants.

    PubMed

    Karthikeyan, S; Sekaran, G

    2014-03-07

    The objective of this investigation is to evaluate the hydroxyl radical (˙OH) generation using nanoporous activated carbon (NPAC), derived from rice husk, and dissolved oxygen in water. The in situ production of the ˙OH radical was confirmed through the DMPO spin trapping method in EPR spectroscopy and quantitative determination by a deoxyribose assay procedure. NPAC served as a heterogeneous catalyst to degrade 2-deoxy-d-ribose (a reference compound) using hydroxyl radical generated from dissolved oxygen in water at temperatures in the range 313-373 K and pH 6, with first order rate constants (k = 9.2 × 10(-2) min(-1), k = 1.2 × 10(-1) min(-1), k = 1.3 × 10(-1) min(-1) and k = 1.68 × 10(-1) min(-1)). The thermodynamic constants for the generation of hydroxyl radicals by NPAC and dissolved oxygen in water were ΔG -1.36 kJ mol(-1) at 313 K, ΔH 17.73 kJ mol(-1) and ΔS 61.01 J mol(-1) K(-1).

  6. Hydroxyl Radical and Its Scavengers in Health and Disease

    PubMed Central

    Lipinski, Boguslaw

    2011-01-01

    It is generally believed that diseases caused by oxidative stress should be treated with antioxidants. However, clinical trials with such antioxidants as ascorbic acid and vitamin E, failed to produce the expected beneficial results. On the other hand, important biomolecules can be modified by the introduction of oxygen atoms by means of non-oxidative hydroxyl radicals. In addition, hydroxyl radicals can reduce disulfide bonds in proteins, specifically fibrinogen, resulting in their unfolding and scrambled refolding into abnormal spatial configurations. Consequences of this reaction are observed in many diseases such as atherosclerosis, cancer and neurological disorders, and can be prevented by the action of non-reducing substances. Moreover, many therapeutic substances, traditionally classified as antioxidants, accept electrons and thus are effective oxidants. It is described in this paper that hydroxyl radicals can be generated by ferric ions without any oxidizing agent. In view of the well-known damaging effect of poorly chelated iron in the human body, numerous natural products containing iron binding agents can be essential in the maintenance of human health. However, beneficial effects of the great number of phytochemicals that are endowed with hydroxyl radical scavenging and/or iron chelating activities should not be considered as a proof for oxidative stress. PMID:21904647

  7. Experimental evidence for efficient hydroxyl radical regeneration in isoprene oxidation

    NASA Astrophysics Data System (ADS)

    Fuchs, H.; Hofzumahaus, A.; Rohrer, F.; Bohn, B.; Brauers, T.; Dorn, H.-P.; Häseler, R.; Holland, F.; Kaminski, M.; Li, X.; Lu, K.; Nehr, S.; Tillmann, R.; Wegener, R.; Wahner, A.

    2013-12-01

    Most pollutants in the Earth's atmosphere are removed by oxidation with highly reactive hydroxyl radicals. Field measurements have revealed much higher concentrations of hydroxyl radicals than expected in regions with high loads of the biogenic volatile organic compound isoprene. Different isoprene degradation mechanisms have been proposed to explain the high levels of hydroxyl radicals observed. Whether one or more of these mechanisms actually operates in the natural environment, and the potential impact on climate and air quality, has remained uncertain. Here, we present a complete set of measurements of hydroxyl and peroxy radicals collected during isoprene-oxidation experiments carried out in an atmospheric simulation chamber, under controlled atmospheric conditions. We detected significantly higher concentrations of hydroxyl radicals than expected based on model calculations, providing direct evidence for a strong hydroxyl radical enhancement due to the additional recycling of radicals in the presence of isoprene. Specifically, our findings are consistent with the unimolecular reactions of isoprene-derived peroxy radicals postulated by quantum chemical calculations. Our experiments suggest that more than half of the hydroxyl radicals consumed in isoprene-rich regions, such as forests, are recycled by these unimolecular reactions with isoprene. Although such recycling is not sufficient to explain the high concentrations of hydroxyl radicals observed in the field, we conclude that it contributes significantly to the oxidizing capacity of the atmosphere in isoprene-rich regions.

  8. Hydroxyl radical scavengers inhibit human lectin-dependent cellular cytotoxicity.

    PubMed

    Melinn, M; McLaughlin, H

    1986-06-01

    The role of oxygen-derived free radicals (ODFR) in lectin-dependent cellular cytotoxicity (LDCC) in humans was investigated. The hydroxyl radical traps thiourea, methanol, ethanol and phenol were effective in inhibiting LDCC, as was DABCO, a singlet oxygen quencher. The proposed pathway of hydroxyl radical production in living cells is either an iron catalysed Haber-Weiss reaction or a Fenton reaction. The effect of inhibitors of these pathways was investigated. The superoxide anion scavengers superoxide dismutase, ferricytochrome c and Tiron were without effect. It was shown that Tiron inhibits the lucigenin-amplified chemiluminescence produced by the action of xanthine oxidase, and also the lucigenin-amplified chemiluminescence produced by activated PMN, suggesting that this agent (Tiron) scavenges intracellular superoxide anion. Catalase gave slight inhibition of LDCC only. The ferric iron chelator desferrioxamine gave no protection of the target cells, while the ferrous chelator, 1,10-phenanthroline, inhibited LDCC and partially prevented the detection of hydroxyl radicals generated by the Fe2+-H2O2 system. Cibacron blue, an agent that inhibits NAD(P)H linked enzymes, also inhibited LDCC. The cyclo-oxygenase inhibitors indomethacin and salicylate were without effect, while the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) inhibited cytolysis. None of the LDCC inhibitors was cytotoxic to the effector cells or to the target cells, neither did they inhibit lymphocyte-target binding. The findings would suggest that hydroxyl radicals have a role to play in human T-cell mediated cytolysis, either as the active lytic agent or as an epiphenomenon.

  9. Hydroxyl radical induced transformation of phenylurea herbicides: A theoretical study

    NASA Astrophysics Data System (ADS)

    Mile, Viktória; Harsányi, Ildikó; Kovács, Krisztina; Földes, Tamás; Takács, Erzsébet; Wojnárovits, László

    2017-03-01

    Aromatic ring hydroxylation reactions occurring during radiolysis of aqueous solutions are studied on the example of phenylurea herbicides by Density Functional Theory calculations. The effect of the aqueous media is taken into account by using the Solvation Model Based on Density model. Hydroxyl radical adds to the ring because the activation free energies (0.4-47.2 kJ mol-1) are low and also the Gibbs free energies have high negative values ((-27.4) to (-5.9) kJ mol-1). According to the calculations in most of cases the ortho- and para-addition is preferred in agreement with the experimental results. In these reactions hydroxycyclohexadienyl type radicals form. In a second type reaction, when loss of chlorine atom takes place, OH/Cl substitution occurs without cyclohexadienyl type intermediate.

  10. Petroleum films exposed to sunlight produce hydroxyl radical.

    PubMed

    Ray, Phoebe Z; Tarr, Matthew A

    2014-05-01

    Sunlight exposed oil films on seawater or pure water produced substantial amounts of hydroxyl radical as a result of irradiation. Oil was collected from the surface of the Gulf of Mexico following the Deepwater Horizon spill and exposed to simulated sunlight in thin films over water. Photochemical production of hydroxyl radical was measured with benzoic acid as a selective chemical probe in the aqueous layer. Total hydroxyl radical formation was studied using high benzoic acid concentrations and varying exposure time. The total amount of hydroxyl radical produced in 24 h irradiations of thin oil films over Gulf of Mexico water and pure water were 3.7×10(-7) and 4.2×10(-7) moles respectively. Steady state concentrations of hydroxyl radical were measured using a competition kinetics approach. Hydroxyl radical concentrations of 1.2×10(-16) to 2.4×10(-16) M were observed for seawater and pure water under oil films. Titanium dioxide (TiO2) nanomaterials were added to the system in an effort to determine if the photocatalyst would enhance oil photodegradation. The addition of TiO2 nanoparticles dramatically changed the observed formation rate of hydroxyl radical in the systems with NP water at pH 3, showing increased formation rate in many cases. With photocatalyst, the steady state concentration of radical decreased, predominantly due to an increase in the hydroxyl radical scavenging rate with oxide present. This study illustrates that oil is a strong and important source of hydroxyl radical when exposed to sunlight. The fate of oil and other dissolved species following oil spills will be heavily dependent on the formation and fate of hydroxyl radical.

  11. Hydroxyl Radical Dosimetry for High Flux Hydroxyl Radical Protein Footprinting Applications Using a Simple Optical Detection Method.

    PubMed

    Xie, Boer; Sharp, Joshua S

    2015-11-03

    Hydroxyl radical protein footprinting (HRPF) by fast photochemical oxidation of proteins (FPOP) is a powerful benchtop tool used to probe protein structure, interactions, and conformational changes in solution. However, the reproducibility of all HRPF techniques is limited by the ability to deliver a defined concentration of hydroxyl radicals to the protein. This ability is impacted by both the amount of radical generated and the presence of radical scavengers in solution. In order to compare HRPF data from sample to sample, a hydroxyl radical dosimeter is needed that can measure the effective concentration of radical that is delivered to the protein, after accounting for both differences in hydroxyl radical generation and nonanalyte radical consumption. Here, we test three radical dosimeters (Alexa Fluor 488, terepthalic acid, and adenine) for their ability to quantitatively measure the effective radical dose under the high radical concentration conditions of FPOP. Adenine has a quantitative relationship between UV spectrophotometric response, effective hydroxyl radical dose delivered, and peptide and protein oxidation levels over the range of radical concentrations typically encountered in FPOP. The simplicity of an adenine-based dosimeter allows for convenient and flexible incorporation into FPOP applications, and the ability to accurately measure the delivered radical dose will enable reproducible and reliable FPOP across a variety of platforms and applications.

  12. Calcium- and potassium-permeable plasma membrane transporters are activated by copper in Arabidopsis root tips: linking copper transport with cytosolic hydroxyl radical production.

    PubMed

    Rodrigo-Moreno, Ana; Andrés-Colás, Nuria; Poschenrieder, Charlotte; Gunsé, Benet; Peñarrubia, Lola; Shabala, Sergey

    2013-04-01

    Transition metals such as copper can interact with ascorbate or hydrogen peroxide to form highly reactive hydroxyl radicals (OH(•) ), with numerous implications to membrane transport activity and cell metabolism. So far, such interaction was described for extracellular (apoplastic) space but not cytosol. Here, a range of advanced electrophysiological and imaging techniques were applied to Arabidopsis thaliana plants differing in their copper-transport activity: Col-0, high-affinity copper transporter COPT1-overexpressing (C1(OE) ) seedlings, and T-DNA COPT1 insertion mutant (copt1). Low Cu concentrations (10 µm) stimulated a dose-dependent Gd(3+) and verapamil sensitive net Ca(2+) influx in the root apex but not in mature zone. C1(OE) also showed a fivefold higher Cu-induced K(+) efflux at the root tip level compared with Col-0, and a reduction in basal peroxide accumulation at the root tip after copper exposure. Copper caused membrane disruptions of the root apex in C1(OE) seedlings but not in copt1 plants; this damage was prevented by pretreatment with Gd(3+) . Our results suggest that copper transport into cytosol in root apex results in hydroxyl radical generation at the cytosolic side, with a consequent regulation of plasma membrane OH(•) -sensitive Ca(2+) and K(+) transport systems.

  13. Hydroxyl radical mediated DNA base modification by manmade mineral fibres.

    PubMed Central

    Leanderson, P; Söderkvist, P; Tagesson, C

    1989-01-01

    Manmade mineral fibres (MMMFs) were examined for their ability to hydroxylate 2-deoxyguanosine (dG) to 8-hydroxydeoxyguanosine (8-OH-dG), a reaction that is mediated by hydroxyl radicals. It appeared that (1) catalase and the hydroxyl radical scavengers, dimethylsulphoxide and sodium benzoate, inhibited the hydroxylation, whereas Fe2+ and H2O2 potentiated it; (2) pretreatment of MMMFs with the iron chelator, deferoxamine, or with extensive heat (200-400 degrees C), attenuated the hydroxylation; (3) the hydroxylation obtained by various MMMFs varied considerably; (4) there was no apparent correlation between the hydroxylation and the surface area of different MMMFs, although increasing the surface area of a fibre by crushing it increased its hydroxylating capacity; and (5) there was good correlation between the hydroxylation of dG residues in DNA and the hydroxylation of pure dG in solution for the 16 different MMMFs investigated. These findings indicate that MMMFs cause a hydroxyl radical mediated DNA base modification in vitro and that there is considerable variation in the reactivity of different fibre species. The DNA modifying ability seems to depend on physical or chemical characteristics, or both, of the fibre. PMID:2765416

  14. Improving Free Radical Scavenging Activity of Soy Isoflavone Glycosides Daidzin and Genistin by 3'-Hydroxylation Using Recombinant Escherichia coli.

    PubMed

    Chiang, Chien-Min; Wang, Dong-Sheng; Chang, Te-Sheng

    2016-12-15

    The present study describes the biotransformation of a commercially available crude extract of soy isoflavones, which contained significant amounts of the soy isoflavone glycosides daidzin and genistin, by recombinant Escherichia coli expressing tyrosinase from Bacillus megaterium. Two major products were isolated from the biotransformation and identified as 3'-hydroxydaidzin and 3'-hydroxygenistin, respectively, based on their mass and nuclear magnetic resonance spectral data. The two 3'-hydroxyisoflavone glycosides showed potent 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity with IC50 values of 7.4 and 9.8 μM for 3'-hydroxydaidzin and 3'-hydroxygenistin, respectively. The free radical scavenging activities of the two 3'-hydroxyisoflavone glycosides were, respectively, 120 and 72 times higher than the activity of their precursors, daidzin and genistin, and were also stronger than the activity of ascorbic acid, which showed an IC50 value of 15.1 μM. This is the first report of the bio-production and potential antioxidant applications of both 3'-hydroxydaidzin and 3'-hydroxygenistin.

  15. Hemibonding of hydroxyl radical and halide anion in aqueous solution.

    PubMed

    Yamaguchi, Makoto

    2011-12-29

    Molecular geometries and properties of the possible reaction products between the hydroxyl radical and the halide anions in aqueous solution were investigated. The formation of two-center three-electron bonding (hemibonding) between the hydroxyl radical and halide anions (Cl, Br, I) was examined by density functional theory (DFT) calculation with a range-separated hybrid (RSH) exchange-correlation functional. The long-range corrected hybrid functional (LC-ωPBE), which have given quantitatively satisfactory results for odd electron systems and excited states, was examined by test calculations for dihalogen radical anions (X(2)(-); X = Cl, Br, I) and hydroxyl radical-water clusters. Equilibrium geometries with hemibonding between the hydroxyl radical and halide anions were located by including four hydrogen-bonded water molecules. Excitation energies and oscillator strengths of σ-σ* transitions calculated by the time-dependent DFT method showed good agreement with observed values. Calculated values of the free energy of reaction on the formation of hydroxyl halide radical anion from the hydroxyl radical and halide anion were endothermic for chloride but exothermic for bromide and iodide, which is consistent with experimental values of equilibrium constants.

  16. Hydroxyl radical-mediated conversion of morphine to morphinone.

    PubMed

    Kumagai, Y; Ikeda, Y; Toki, S

    1992-05-01

    1. The hydroxyl radical-mediated conversion of morphine to morphinone (MO) was examined as an alternative to the enzymic reaction. 2. Hydroxyl radicals were generated by autoxidation of ascorbate in the presence of iron and EDTA. This system oxidized morphine to MO which was identified by h.p.l.c. and t.l.c. The reaction was dependent on the concentration of added Fe2+ and required the addition of ascorbate when Fe3+ was used. 3. Catalase inhibited production of MO whereas superoxide dismutase (SOD) had no effect. Addition of a large amount of H2O2 to the system resulted in a significant decrease in production of MO. No MO production was initiated by H2O2 itself. The oxidation of morphine was inhibited by typical hydroxyl radical-scavenging agents. These results indicate that morphine undergoes oxidation to MO by hydroxyl radical.

  17. Hydroxyl radical production in plasma electrolysis with KOH electrolyte solution

    SciTech Connect

    Saksono, Nelson; Febiyanti, Irine Ayu Utami, Nissa; Ibrahim

    2015-12-29

    Plasma electrolysis is an effective technology for producing hydroxyl radical (•OH). This method can be used for waste degradation process. This study was conducted to obtain the influence of applied voltage, electrolyte concentration, and anode depth in the plasma electrolysis system for producing hydroxyl radical. The materials of anode and cathode, respectively, were made from tungsten and stainless steel. KOH solution was used as the solution. Determination of hydroxyl radical production was done by measuring H{sub 2}O{sub 2} amount formed in plasma system using an iodometric titration method, while the electrical energy consumed was obtained by measuring the electrical current throughout the process. The highest hydroxyl radical production was 3.51 mmol reached with 237 kJ energy consumption in the power supply voltage 600 V, 0.02 M KOH, and 0.5 cm depth of anode.

  18. Hydroxyl radical production in plasma electrolysis with KOH electrolyte solution

    NASA Astrophysics Data System (ADS)

    Saksono, Nelson; Febiyanti, Irine Ayu; Utami, Nissa; Ibrahim

    2015-12-01

    Plasma electrolysis is an effective technology for producing hydroxyl radical (•OH). This method can be used for waste degradation process. This study was conducted to obtain the influence of applied voltage, electrolyte concentration, and anode depth in the plasma electrolysis system for producing hydroxyl radical. The materials of anode and cathode, respectively, were made from tungsten and stainless steel. KOH solution was used as the solution. Determination of hydroxyl radical production was done by measuring H2O2 amount formed in plasma system using an iodometric titration method, while the electrical energy consumed was obtained by measuring the electrical current throughout the process. The highest hydroxyl radical production was 3.51 mmol reached with 237 kJ energy consumption in the power supply voltage 600 V, 0.02 M KOH, and 0.5 cm depth of anode.

  19. Adenine oxidation by pyrite-generated hydroxyl radicals.

    PubMed

    Cohn, Corey A; Fisher, Shawn C; Brownawell, Bruce J; Schoonen, Martin Aa

    2010-04-26

    Cellular exposure to particulate matter with concomitant formation of reactive oxygen species (ROS) and oxidization of biomolecules may lead to negative health outcomes. Evaluating the particle-induced formation of ROS and the oxidation products from reaction of ROS with biomolecules is useful for gaining a mechanistic understanding of particle-induced oxidative stress. Aqueous suspensions of pyrite particles have been shown to form hydroxyl radicals and degrade nucleic acids. Reactions between pyrite-induced hydroxyl radicals and nucleic acid bases, however, remain to be determined. Here, we compared the oxidation of adenine by Fenton-generated (i.e., ferrous iron and hydrogen peroxide) hydroxyl radicals to adenine oxidation by hydroxyl radicals generated in pyrite aqueous suspensions. Results show that adenine oxidizes in the presence of pyrite (without the addition of hydrogen peroxide) and that the rate of oxidation is dependent on the pyrite loading. Adenine oxidation was prevented by addition of either catalase or ethanol to the pyrite/adenine suspensions, which implies that hydrogen peroxide and hydroxyl radicals are causing the adenine oxidation. The adenine oxidation products, 8-oxoadenine and 2-hydroxyadenine, were the same whether hydroxyl radicals were generated by Fenton or pyrite-initiated reactions. Although nucleic acid bases are unlikely to be directly exposed to pyrite particles, the formation of ROS in the vicinity of cells may lead to oxidative stress.

  20. Chemical repair activity of free radical scavenger edaravone: reduction reactions with dGMP hydroxyl radical adducts and suppression of base lesions and AP sites on irradiated plasmid DNA.

    PubMed

    Hata, Kuniki; Urushibara, Ayumi; Yamashita, Shinichi; Lin, Mingzhang; Muroya, Yusa; Shikazono, Naoya; Yokoya, Akinari; Fu, Haiying; Katsumura, Yosuke

    2015-01-01

    Reactions of edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) with deoxyguanosine monophosphate (dGMP) hydroxyl radical adducts were investigated by pulse radiolysis technique. Edaravone was found to reduce the dGMP hydroxyl radical adducts through electron transfer reactions. The rate constants of the reactions were greater than 4 × 10(8) dm(3) mol(-1) s(-1) and similar to those of the reactions of ascorbic acid, which is a representative antioxidant. Yields of single-strand breaks, base lesions, and abasic sites produced in pUC18 plasmid DNA by gamma ray irradiation in the presence of low concentrations (10-1000 μmol dm(-3)) of edaravone were also quantified, and the chemical repair activity of edaravone was estimated by a method recently developed by the authors. By comparing suppression efficiencies to the induction of each DNA lesion, it was found that base lesions and abasic sites were suppressed by the chemical repair activity of edaravone, although the suppression of single-strand breaks was not very effective. This phenomenon was attributed to the chemical repair activity of edaravone toward base lesions and abasic sites. However, the chemical repair activity of edaravone for base lesions was lower than that of ascorbic acid.

  1. Hydroxyl radical Thymine adduct induced DNA damages

    NASA Astrophysics Data System (ADS)

    Schyman, Patric; Eriksson, Leif A.; Zhang, Ru bo; Laaksonen, Aatto

    2008-06-01

    DNA damages caused by a 5-hydroxy-5,6-dihydrothymine-6-yl radical (5-OHT-6yl) abstracting a C2‧ hydrogen from a neighboring sugar (inter-H abstraction) have been theoretically investigated using hybrid DFT in gas phase and in water solution. The inter-H abstraction was here shown to be comparable in energy (24 kcal mol-1) with the intra-H abstraction in which the 5-OHT-6yl abstracts a C2‧ hydrogen from its own sugar. The effect of a neutrally or a negatively charged phosphate group was also studied and the results show no significant impact on the activation energy of the hydrogen abstraction whereas base release and strand break reactions are affected.

  2. Mechanisms of hydroxyl radical-induced contraction of rat aorta.

    PubMed

    Li, Jianfeng; Li, Wenyan; Liu, Weimin; Altura, Bella T; Altura, Burton M

    2004-09-19

    The present study was designed to investigate the effects of hydroxyl radicals (*OH), generated via the Fe2+-mediated Fenton reaction, on isolated rat aortic rings with and without endothelium. In the absence of any vasoactive agent, generation of *OH alone elicited an endothelium-independent contraction in rat aortic rings in a concentration-dependent manner. Hydroxyl radical-induced contractions of denuded rat aortic rings appeared, however, to be slightly stronger than those on intact rat aortic rings. The contractile responses to *OH were neither reversible nor reproducible in the same ring; even small concentrations of *OH radicals resulted in tachyphylaxis. Removal of extracellular calcium ions (Ca2+) or buffering intracellular Ca2+ with 10 microM acetyl methyl ester of bis(o-aminophenoxy) ethane-N,N,N',N',-tetraacetic acid (BAPTA-AM) significantly attenuated the contractile actions of *OH radicals. The presence of 1 microM staurosporine, 1 microM bisindolylmaleimide I, 1 microM Gö6976 [inhibitor of protein kinase C (PKC)], 2 microM PD-980592 (inhibitor of ERK), 10 microM genistein, and 1 microM wortmannin significantly inhibited the contractions induced by *OH. Proadifen (10 microM), on the other hand, significantly potentiated the hydroxyl radical-induced contractions. Exposure of primary cultured aortic smooth muscle cells to *OH produced significant, rapid rises of intracellular free Ca2+ ([Ca2+]i). Several, specific antagonists of possible endogenously formed vasoconstrictors did not inhibit or attenuate either hydroxyl radical-induced contractions or the elevation of [Ca2+]i. Our new results suggest that hydroxyl radical-triggered contractions on rat aortic rings are Ca2+-dependent. Several intracellular signal transduction systems seem to play some role in hydroxyl radical-induced vasoconstriction of rat aortic rings.

  3. Hydrogen peroxide and dioxygen activation by dinuclear copper complexes in aqueous solution: hydroxyl radical production initiated by internal electron transfer.

    PubMed

    Zhu, Qing; Lian, Yuxiang; Thyagarajan, Sunita; Rokita, Steven E; Karlin, Kenneth D; Blough, Neil V

    2008-05-21

    Dinuclear Cu(II) complexes, CuII2Nn (n = 4 or 5), were recently found to specifically cleave DNA in the presence of a reducing thiol and O2 or in the presence of H2O2 alone. However, CuII2N3 and a closely related mononuclear Cu(II) complex exhibited no selective reaction under either condition. Spectroscopic studies indicate an intermediate is generated from CuII2Nn (n = 4 or 5) and mononuclear Cu(II) solutions in the presence of H2O2 or from CuI2Nn (n = 4 or 5) in the presence of O2. This intermediate decays to generate OH radicals and ligand degradation products at room temperature. The lack of reactivity of the intermediate with a series of added electron donors suggests the intermediate discharges through a rate-limiting intramolecular electron transfer from the ligand to the metal peroxo center to produce an OH radical and a ligand-based radical. These results imply that DNA cleavage does not result from direct reaction with a metal-peroxo intermediate but instead arises from reaction with either OH radicals or ligand-based radicals.

  4. Iron chlorin e6 scavenges hydroxyl radical and protects human endothelial cells against hydrogen peroxide toxicity.

    PubMed

    Yu, J W; Yoon, S S; Yang, R

    2001-09-01

    Iron chlorin e6 (FeCe6) has recently been proposed to be potentially antimutagenic and antioxidative. However, the antioxidant property of FeCe6 has not been elucidated in detail. In this study, we investigated the ability of FeCe6 to scavenge hydroxyl radical and to protect biomolecules and mammalian cells from oxidative stress-mediated damage. In electron spin resonance (ESR) experiments, FeCe6 showed excellent hydroxyl radical scavenging activity, whereas its iron-deficient molecule, chlorin e6 (Ce6) showed little effect. FeCe6 also significantly reduced hydroxyl radical-induced thiobarbituric acid reactive substance (TBARS) formation and benzoate hydroxylation in a dose-dependent manner. The rate constant for reaction between FeCe6 and hydroxyl radical was measured as 8.5 x 10(10) M(-1) s(-1) by deoxyribose degradation method, and this value was much higher than that of most hydroxyl radical scavengers. Superoxide dismutase (SOD) activity of FeCe6 was also confirmed by ESR study and cytochrome c reduction assay, but its in vitro activity appeared to be less efficient in comparison with other well-known SOD mimics. In addition, FeCe6 appreciably diminished hydroxyl radical-induced DNA single-strand breakage and protein degradation in Fe-catalyzed and Cu-catalyzed Fenton systems, and it significantly protected human endothelial cells against hydrogen peroxide (H2O2) toxicity. These results suggest that FeCe6 is a novel hydroxyl radical scavenger and may be useful for preventing oxidative injury in biological systems.

  5. Hydroxyl radical-induced formation of highly oxidized organic compounds

    NASA Astrophysics Data System (ADS)

    Berndt, Torsten; Richters, Stefanie; Jokinen, Tuija; Hyttinen, Noora; Kurtén, Theo; Otkjær, Rasmus V.; Kjaergaard, Henrik G.; Stratmann, Frank; Herrmann, Hartmut; Sipilä, Mikko; Kulmala, Markku; Ehn, Mikael

    2016-12-01

    Explaining the formation of secondary organic aerosol is an intriguing question in atmospheric sciences because of its importance for Earth's radiation budget and the associated effects on health and ecosystems. A breakthrough was recently achieved in the understanding of secondary organic aerosol formation from ozone reactions of biogenic emissions by the rapid formation of highly oxidized multifunctional organic compounds via autoxidation. However, the important daytime hydroxyl radical reactions have been considered to be less important in this process. Here we report measurements on the reaction of hydroxyl radicals with α- and β-pinene applying improved mass spectrometric methods. Our laboratory results prove that the formation of highly oxidized products from hydroxyl radical reactions proceeds with considerably higher yields than previously reported. Field measurements support these findings. Our results allow for a better description of the diurnal behaviour of the highly oxidized product formation and subsequent secondary organic aerosol formation in the atmosphere.

  6. Hydroxyl radical-induced formation of highly oxidized organic compounds

    PubMed Central

    Berndt, Torsten; Richters, Stefanie; Jokinen, Tuija; Hyttinen, Noora; Kurtén, Theo; Otkjær, Rasmus V.; Kjaergaard, Henrik G.; Stratmann, Frank; Herrmann, Hartmut; Sipilä, Mikko; Kulmala, Markku; Ehn, Mikael

    2016-01-01

    Explaining the formation of secondary organic aerosol is an intriguing question in atmospheric sciences because of its importance for Earth's radiation budget and the associated effects on health and ecosystems. A breakthrough was recently achieved in the understanding of secondary organic aerosol formation from ozone reactions of biogenic emissions by the rapid formation of highly oxidized multifunctional organic compounds via autoxidation. However, the important daytime hydroxyl radical reactions have been considered to be less important in this process. Here we report measurements on the reaction of hydroxyl radicals with α- and β-pinene applying improved mass spectrometric methods. Our laboratory results prove that the formation of highly oxidized products from hydroxyl radical reactions proceeds with considerably higher yields than previously reported. Field measurements support these findings. Our results allow for a better description of the diurnal behaviour of the highly oxidized product formation and subsequent secondary organic aerosol formation in the atmosphere. PMID:27910849

  7. Silver nanoparticles induce apoptotic cell death in Candida albicans through the increase of hydroxyl radicals.

    PubMed

    Hwang, In-sok; Lee, Juneyoung; Hwang, Ji Hong; Kim, Keuk-Jun; Lee, Dong Gun

    2012-04-01

    Silver nanoparticles have been shown to be detrimental to fungal cells although the mechanism(s) of action have not been clearly established. In this study, we used Candida albicans cells to show that silver nanoparticles exert their antifungal effect through apoptosis. Many studies have shown that the accumulation of reactive oxygen species induces and regulates the induction of apoptosis. Furthermore, hydroxyl radicals are considered an important component of cell death. Therefore, we assumed that hydroxyl radicals were related to apoptosis and the effect of thiourea as a hydroxyl radical scavenger was investigated. We measured the production of reactive oxygen species and investigated whether silver nanoparticles induced the accumulation of hydroxyl radicals. A reduction in the mitochondrial membrane potential shown by flow cytometry analysis and the release of cytochrome c from mitochondria were also verified. In addition, the apoptotic effects of silver nanoparticles were detected by fluorescence microscopy using other confirmed diagnostic markers of yeast apoptosis including phosphatidylserine externalization, DNA and nuclear fragmentation, and the activation of metacaspases. Cells exposed to silver nanoparticles showed increased reactive oxygen species and hydroxyl radical production. All other phenomena of mitochondrial dysfunction and apoptotic features also appeared. The results indicate that silver nanoparticles possess antifungal effects with apoptotic features and we suggest that the hydroxyl radicals generated by silver nanoparticles have a significant role in mitochondrial dysfunctional apoptosis.

  8. Radiocarbon tracer measurements of atmospheric hydroxyl radical concentrations

    NASA Technical Reports Server (NTRS)

    Campbell, M. J.; Farmer, J. C.; Fitzner, C. A.; Henry, M. N.; Sheppard, J. C.

    1986-01-01

    The usefulness of the C-14 tracer in measurements of atmospheric hydroxyl radical concentration is discussed. The apparatus and the experimental conditions of three variations of a radiochemical method of atmosphere analysis are described and analyzed: the Teflon bag static reactor, the flow reactor (used in the Wallops Island tests), and the aircraft OH titration reactor. The procedure for reduction of the aircraft reactor instrument data is outlined. The problems connected with the measurement of hydroxyl radicals are discussed. It is suggested that the gas-phase radioisotope methods have considerable potential in measuring tropospheric impurities present in very low concentrations.

  9. Quenching Dynamics of Electronically Excited Hydroxyl Radicals

    DTIC Science & Technology

    2008-05-19

    the research of graduate students Margaret Greenslade , Erika Derro, Ilana Pollack, Logan Dempsey, and Eunice Li. In addition, postdoctoral...acknowledging AFOSR support 1) M. E. Greenslade , M. 1. Lester, D. C. Radenovi6, A. J. A. van Roij, and D. H. Parker, "(2+1) Resonance Enhanced Ionization...Spectroscopy of a State Selected Beam of OH Radicals", J. Chem. Phys. 123, 074309 (2005). 4 2) E. L. Derro, I. B. Pollack, L. Dempsey, M. E. Greenslade , Y

  10. Hydroxyl radical reactivity at the air-ice interface

    NASA Astrophysics Data System (ADS)

    Kahan, T. F.; Zhao, R.; Donaldson, D. J.

    2010-01-01

    Hydroxyl radicals are important oxidants in the atmosphere and in natural waters. They are also expected to be important in snow and ice, but their reactivity has not been widely studied in frozen aqueous solution. We have developed a spectroscopic probe to monitor the formation and reactions of hydroxyl radicals in situ. Hydroxyl radicals are produced in aqueous solution via the photolysis of nitrite, nitrate, and hydrogen peroxide, and react rapidly with benzene to form phenol. Similar phenol formation rates were observed in aqueous solution and bulk ice. However, no reaction was observed at air-ice interfaces, or when bulk ice samples were crushed prior to photolysis to increase their surface area. We also monitored the heterogeneous reaction between benzene present at air-water and air-ice interfaces with gas-phase OH produced from HONO photolysis. Rapid phenol formation was observed on water surfaces, but no reaction was observed at the surface of ice. Under the same conditions, we observed rapid loss of the polycyclic aromatic hydrocarbon (PAH) anthracene at air-water interfaces, but no loss was observed at air-ice interfaces. Our results suggest that the reactivity of hydroxyl radicals toward aromatic organics is similar in bulk ice samples and in aqueous solution, but is significantly suppressed in the quasi-liquid layer (QLL) that exists at air-ice interfaces.

  11. Hydroxyl radical reactivity at the air-ice interface

    NASA Astrophysics Data System (ADS)

    Kahan, T. F.; Zhao, R.; Donaldson, D. J.

    2009-10-01

    Hydroxyl radicals are important oxidants in the atmosphere and in natural waters. They are also expected to be important in snow and ice, but their reactivity has not been widely studied in frozen aqueous solution. We have developed a spectroscopic probe to monitor the formation and reactions of hydroxyl radicals in situ. Hydroxyl radicals are produced in aqueous solution via the photolysis of nitrite, nitrate, and hydrogen peroxide, and react rapidly with benzene to form phenol. Similar phenol formation rates were observed in aqueous solution and bulk ice. However, no reaction was observed at the air-ice interface, or when bulk ice samples were crushed prior to photolysis to increase their surface area. We also monitored the heterogeneous reaction between benzene present at air-water and air-ice interfaces with gas-phase OH produced from HONO photolysis. Rapid phenol formation was observed on water surfaces, but no reaction was observed at the surface of ice. Under the same conditions, we observed rapid loss of the polycyclic aromatic hydrocarbon (PAH) anthracene at the air-water interface, but no loss was observed at the air-ice interface. Our results suggest that the reactivity of hydroxyl radicals toward aromatic organics is similar in bulk ice samples and in aqueous solution, but is significantly suppressed in the quasi-liquid layer (QLL) that exists at the air-ice interface.

  12. Visible light activity of pulsed layer deposited BiVO4/MnO2 films decorated with gold nanoparticles: The evidence for hydroxyl radicals formation

    NASA Astrophysics Data System (ADS)

    Trzciński, Konrad; Szkoda, Mariusz; Sawczak, Mirosław; Karczewski, Jakub; Lisowska-Oleksiak, Anna

    2016-11-01

    Thin films containing BiVO4 and MnO2 deposited on FTO and modified by Au nanoparticles were studied towards their photoelectrochemical and photocatalytical activities in an aqueous electrolyte. Electrodes were prepared by the pulsed laser deposition (PLD) method. The surfactant-free ablation process was used for preparation of the gold nanoparticles (GNP) water suspension. Obtained layers of varied thicknesses (27-115 nm) were characterized using Raman spectroscopy, UV-vis spectroscopy and scanning electron microscopy. Electrochemical methods such as electrochemical impedance spectroscopy, linear voltammetry and chronoamperometry under visible light illumination and in the dark were applied to characterize layers as photoanodes. Simple modification of the BiVO4 + MnO2 layer by drop-casting of small amount of colloidal gold (1.5 × 10-14 mol of GNP on 1 cm2) leads to enhancement of the generated photocurrent recorded at E = 0.5 V vs. Ag/AgCl (0.1 M KCl) from 63 μA/cm2 to 280 μA/cm2. Photocatalytical studies were also exploited towards decomposition of methylene blue (MB). A possible mechanism of MB photodegradation was proposed. The formation of hydroxyl radicals was detected by photoluminescence spectra using terephthalic acid as the probe molecule.

  13. Photolysis of hydrogen peroxide, an effective disinfection system via hydroxyl radical formation.

    PubMed

    Ikai, Hiroyo; Nakamura, Keisuke; Shirato, Midori; Kanno, Taro; Iwasawa, Atsuo; Sasaki, Keiichi; Niwano, Yoshimi; Kohno, Masahiro

    2010-12-01

    The relationship between the amount of hydroxyl radicals generated by photolysis of H(2)O(2) and bactericidal activity was examined. H(2)O(2) (1 M) was irradiated with laser light at a wavelength of 405 nm to generate hydroxyl radicals. Electron spin resonance spin trapping analysis showed that the amount of hydroxyl radicals produced increased with the irradiation time. Four species of pathogenic oral bacteria, Staphylococcus aureus, Aggregatibacter actinomycetemcomitans, Streptococcus mutans, and Enterococcus faecalis, were used in the bactericidal assay. S. mutans in a model biofilm was also examined. Laser irradiation of suspensions in 1 M H(2)O(2) resulted in a >99.99% reduction of the viable counts of each of the test species within 3 min of treatment. Treatment of S. mutans in a biofilm resulted in a >99.999% reduction of viable counts within 3 min. Other results demonstrated that the bactericidal activity was dependent on the amount of hydroxyl radicals generated. Treatment of bacteria with 200 to 300 μM hydroxyl radicals would result in reductions of viable counts of >99.99%.

  14. Electrochemical DNA biosensor for detection of DNA damage induced by hydroxyl radicals.

    PubMed

    Hájková, Andrea; Barek, Jiří; Vyskočil, Vlastimil

    2017-03-01

    A simple electrochemical DNA biosensor based on a glassy carbon electrode (GCE) was prepared by adsorbing double-stranded DNA (dsDNA) onto the GCE surface and subsequently used for the detection of dsDNA damage induced by hydroxyl radicals. Investigation of the mutual interaction between hydroxyl radicals and dsDNA was conducted using a combination of several electrochemical detection techniques: square-wave voltammetry for direct monitoring the oxidation of dsDNA bases, and cyclic voltammetry and electrochemical impedance spectroscopy as indirect electrochemical methods making use of the redox-active indicator [Fe(CN)6](4-/3-). Hydroxyl radicals were generated electrochemically on the surface of a boron-doped diamond electrode and chemically (via the Fenton's reaction or the auto-oxidation of Fe(II)). The extent of dsDNA damage by electrochemically generated hydroxyl radicals depended on the current density applied to the generating electrode: by applying 5, 10, and 50mAcm(-2), selected relative biosensor responses decreased after 3min incubation from 100% to 38%, 27%, and 3%, respectively. Chemically generated hydroxyl radicals caused less pronounced dsDNA damage, and their damaging activity depended on the form of Fe(II) ions: decreases to 49% (Fenton's reaction; Fe(II) complexed with EDTA) and 33% (auto-oxidation of Fe(II); Fe(II) complexed with dsDNA) were observed after 10min incubation.

  15. Heat shock-induced attenuation of hydroxyl radical generation and mitochondrial aconitase activity in cardiac H9c2 cells.

    PubMed

    Ilangovan, Govindasamy; Venkatakrishnan, C D; Bratasz, Anna; Osinbowale, Sola; Cardounel, Arturo J; Zweier, Jay L; Kuppusamy, Periannan

    2006-02-01

    A mild heat shock (hyperthermia) protects cells from apoptotic and necrotic deaths by inducing overexpression of various heat shock proteins (Hsps). These proteins, in combination with the activation of the nitric oxide synthase (NOS) enzyme, play important roles in the protection of the myocardium against a variety of diseases. In the present work we report that the generation of potent reactive oxygen species (ROS), namely *OH in cardiac H9c2 cells, is attenuated by heat shock treatment (2 h at 42 degrees C). Western blot analyses showed that heat shock treatment induced overexpression of Hsp70, Hsp60, and Hsp25. The observed *OH was found to be derived from the superoxide (O(2)(-)*) generated by the mitochondria. Whereas the manganese superoxide dismutase (MnSOD) activity was increased in the heat-shocked cells, the mitochondrial aconitase activity was reduced. The mechanism of O(2)(-)* conversion into *OH in mitochondria is proposed as follows. The O(2)(-)* leaked from the electron transport chain, oxidatively damages the mitochondrial aconitase, releasing a free Fe(2+). The aconitase-released Fe(2+) combines with H(2)O(2) to generate *OH via a Fenton reaction and the oxidized Fe(3+) recombines with the inactivated enzyme after being reduced to Fe(2+) by other cellular reductants, turning it over to be active. However, in heat-shocked cells, because of higher MnSOD activity, the excess H(2)O(2) causes irreversible damage to the mitochondrial aconitase enzyme, thus inhibiting its activity. In conclusion, we propose that attenuation of *OH generation after heat shock treatment might play an important role in reducing the myocardial ischemic injury, observed in heat shock-treated animals.

  16. Antrodia camphorata Potentiates Neuroprotection against Cerebral Ischemia in Rats via Downregulation of iNOS/HO-1/Bax and Activated Caspase-3 and Inhibition of Hydroxyl Radical Formation

    PubMed Central

    Yang, Po-Sheng; Lin, Po-Yen; Chang, Chao-Chien; Yu, Meng-Che; Yen, Ting-Lin; Lan, Chang-Chou; Jayakumar, Thanasekaran; Yang, Chih-Hao

    2015-01-01

    Antrodia camphorata (A. camphorata) is a fungus generally used in Chinese folk medicine for treatment of viral hepatitis and cancer. Our previous study found A. camphorata has neuroprotective properties and could reduce stroke injury in cerebral ischemia animal models. In this study, we sought to investigate the molecular mechanisms of neuroprotective effects of A. camphorata in middle cerebral artery occlusion (MCAO) rats. A selective occlusion of the middle cerebral artery (MCA) with whole blood clots was used to induce ischemic stroke in rats and they were orally treated with A. camphorata (0.25 and 0.75 g/kg/day) alone or combined with aspirin (5 mg/kg/day). To provide insight into the functions of A. camphorata mediated neuroprotection, the expression of Bax, inducible nitric oxide synthase (iNOS), haem oxygenase-1 (HO-1), and activated caspase-3 was determined by Western blot assay. Treatment of aspirin alone significantly reduced the expressions of HO-1 (P < 0.001), iNOS (P < 0.001), and Bax (P < 0.01) in ischemic regions. The reduction of these expressions was more potentiated when rats treated by aspirin combined with A. camphorata (0.75 g/kg/day). Combination treatment also reduced apoptosis as measured by a significant reduction in active caspase-3 expression in the ischemic brain compared to MCAO group (P < 0.01). Moreover, treatment of A. camphorata significantly (P < 0.05) reduced fenton reaction-induced hydroxyl radical (OH•) formation at a dose of 40 mg/mL. Taken together, A. camphorata has shown neuroprotective effects in embolic rats, and the molecular mechanisms may correlate with the downregulation of Bax, iNOS, HO-1, and activated caspase-3 and the inhibition of OH• signals. PMID:26379739

  17. Antrodia camphorata Potentiates Neuroprotection against Cerebral Ischemia in Rats via Downregulation of iNOS/HO-1/Bax and Activated Caspase-3 and Inhibition of Hydroxyl Radical Formation.

    PubMed

    Yang, Po-Sheng; Lin, Po-Yen; Chang, Chao-Chien; Yu, Meng-Che; Yen, Ting-Lin; Lan, Chang-Chou; Jayakumar, Thanasekaran; Yang, Chih-Hao

    2015-01-01

    Antrodia camphorata (A. camphorata) is a fungus generally used in Chinese folk medicine for treatment of viral hepatitis and cancer. Our previous study found A. camphorata has neuroprotective properties and could reduce stroke injury in cerebral ischemia animal models. In this study, we sought to investigate the molecular mechanisms of neuroprotective effects of A. camphorata in middle cerebral artery occlusion (MCAO) rats. A selective occlusion of the middle cerebral artery (MCA) with whole blood clots was used to induce ischemic stroke in rats and they were orally treated with A. camphorata (0.25 and 0.75 g/kg/day) alone or combined with aspirin (5 mg/kg/day). To provide insight into the functions of A. camphorata mediated neuroprotection, the expression of Bax, inducible nitric oxide synthase (iNOS), haem oxygenase-1 (HO-1), and activated caspase-3 was determined by Western blot assay. Treatment of aspirin alone significantly reduced the expressions of HO-1 (P < 0.001), iNOS (P < 0.001), and Bax (P < 0.01) in ischemic regions. The reduction of these expressions was more potentiated when rats treated by aspirin combined with A. camphorata (0.75 g/kg/day). Combination treatment also reduced apoptosis as measured by a significant reduction in active caspase-3 expression in the ischemic brain compared to MCAO group (P < 0.01). Moreover, treatment of A. camphorata significantly (P < 0.05) reduced fenton reaction-induced hydroxyl radical (OH(•)) formation at a dose of 40 mg/mL. Taken together, A. camphorata has shown neuroprotective effects in embolic rats, and the molecular mechanisms may correlate with the downregulation of Bax, iNOS, HO-1, and activated caspase-3 and the inhibition of OH(•) signals.

  18. Hydroxyl radical induced degradation of salicylates in aerated aqueous solution

    NASA Astrophysics Data System (ADS)

    Szabó, László; Tóth, Tünde; Homlok, Renáta; Rácz, Gergely; Takács, Erzsébet; Wojnárovits, László

    2014-04-01

    Ionizing radiation induced degradation of acetylsalicylic acid, its hydrolysis product salicylic acid and a salicylic acid derivative 5-sulpho-salicylic acid, was investigated in dilute aqueous solutions by UV-vis spectrophotometry, HPLC separation and diode-array or MS/MS detection, chemical oxygen demand, total organic carbon content and by Vibrio fischeri toxicity measurements. Hydroxyl radicals were shown to degrade these molecules readily, and first degradation products were hydroxylated derivatives in all cases. Due to the by-products, among them hydrogen peroxide, the toxicity first increased and then decreased with the absorbed dose. With prolonged irradiation complete mineralization was achieved.

  19. Environmentally persistent free radicals (EPFRs)-2. Are free hydroxyl radicals generated in aqueous solutions?

    PubMed

    Khachatryan, Lavrent; Dellinger, Barry

    2011-11-01

    A chemical spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed to measure the production of hydroxyl radical (·OH) in aqueous suspensions of 5% Cu(II)O/silica (3.9% Cu) particles containing environmentally persistent free radicals (EPFRs) of 2-monochlorophenol (2-MCP). The results indicate: (1) a significant differences in accumulated DMPO-OH adducts between EPFR containing particles and non-EPFR control samples, (2) a strong correlation between the concentration of DMPO-OH adducts and EPFRs per gram of particles, and (3) a slow, constant growth of DMPO-OH concentration over a period of days in solution containing 50 μg/mL EPFRs particles + DMPO (150 mM) + reagent balanced by 200 μL phosphate buffered (pH = 7.4) saline. However, failure to form secondary radicals using standard scavengers, such as ethanol, dimethylsulfoxide, sodium formate, and sodium azide, suggests free hydroxyl radicals may not have been generated in solution. This suggests surface-bound, rather than free, hydroxyl radicals were generated by a surface catalyzed-redox cycle involving both the EPFRs and Cu(II)O. Toxicological studies clearly indicate these bound free radicals promote various types of cardiovascular and pulmonary disease normally attributed to unbound free radicals; however, the exact chemical mechanism deserves further study in light of the implication of formation of bound, rather than free, hydroxyl radicals.

  20. Activation parameters for cyclohexene oxygenation by an oxoiron(IV) porphyrin pi-cation radical complex: entropy control of an allylic hydroxylation reaction.

    PubMed

    Takahashi, Akihiro; Kurahashi, Takuya; Fujii, Hiroshi

    2007-08-06

    Activation parameters for epoxidation and allylic hydroxylation reactions of cyclohexene with FeIVO(TMP)*+Cl (1) were determined. Within the experimental temperature range, the epoxidation reaction was enthalpy-controlled (i.e., DeltaH > -TDeltaS), while the allylic hydroxylation reaction was entropy-controlled (i.e., -TDeltaS > DeltaH). An unexpectedly large contribution of the entropy term for the allylic hydroxylation reaction indicated that the free energy of activation, DeltaG, rather than the activation energy, Ea, should be used to discuss the reaction mechanism and chemoselectivity. The results of this study bring caution to previous density functional theory studies, in which the reaction mechanism and chemoselectivity are evaluated from calculated Ea.

  1. Nanoscale hydroxyl radical generation from multiphoton ionization of tryptophan.

    PubMed

    Bisby, Roger H; Crisostomo, Ana G; Botchway, Stanley W; Parker, Anthony W

    2009-01-01

    Exposure of solutions containing both tryptophan and hydrogen peroxide to a pulsed ( approximately 180 fs) laser beam at 750 nm induces luminescence characteristic of 5-hydroxytryptophan. The results indicate that 3-photon excitation of tryptophan results in photoionization within the focal volume of the laser beam. The resulting hydrated electron is scavenged by hydrogen peroxide to produce the hydroxyl radical. The latter subsequently reacts with tryptophan to form 5-hydroxytryptophan. The involvement of hydroxyl radicals is confirmed by the use of ethanol and nitrous oxide as scavengers and their effects on the fluorescence yield in this system. It is postulated that such multiphoton ionization of tryptophanyl residues in cellular proteins may contribute to the photodamage observed during imaging of cells and tissues using multiphoton microscopy.

  2. Novel denture-cleaning system based on hydroxyl radical disinfection.

    PubMed

    Kanno, Taro; Nakamura, Keisuke; Ikai, Hiroyo; Hayashi, Eisei; Shirato, Midori; Mokudai, Takayuki; Iwasawa, Atsuo; Niwano, Yoshimi; Kohno, Masahiro; Sasaki, Keiichi

    2012-01-01

    The purpose of this study was to evaluate a new denture-cleaning device using hydroxyl radicals generated from photolysis of hydrogen peroxide (H2O2). Electron spin resonance analysis demonstrated that the yield of hydroxyl radicals increased with the concentration of H2O2 and light irradiation time. Staphylococcus aureus, Pseudomonas aeruginosa, and methicillin-resistant S aureus were killed within 10 minutes with a > 5-log reduction when treated with photolysis of 500 mM H2O2; Candida albicans was killed within 30 minutes with a > 4-log reduction with photolysis of 1,000 mM H2O2. The clinical test demonstrated that the device could effectively reduce microorganisms in denture plaque by approximately 7-log order within 20 minutes.

  3. Treating ballast water with hydroxyl radical on introduced organisms

    NASA Astrophysics Data System (ADS)

    Zhang, Zhitao; Bai, Mindi; Xiao, Yu; Bai, Mindong; Yang, Bo; Bai, Xiyao

    2006-06-01

    With physical method of micro-gap gas discharge, a large amount of hydroxyl radical can be produced in 20t/h pilot-scale system using the ionization of O2 and H2O. In this paper, the effect of biochemistry of hydroxyl radicals on introduced organisms in ballast water was experimentally investigated. The results indicate that the contents of chlorophyl- a, chlorophyl- b, chlorophyl- c and carotenoid are decreased by 35% 64% within 8.0s and further to the lowest limit of test 5 minutes. In addition, the main reasons of cell death are the lipid peroxidation, the strong destruction to the monose, amylose, protein, DNA and RNA of cell, and damage in CAT, POD and SOD of antioxidant enzyme system.

  4. Glutathione--hydroxyl radical interaction: a theoretical study on radical recognition process.

    PubMed

    Fiser, Béla; Jójárt, Balázs; Csizmadia, Imre G; Viskolcz, Béla

    2013-01-01

    Non-reactive, comparative (2 × 1.2 μs) molecular dynamics simulations were carried out to characterize the interactions between glutathione (GSH, host molecule) and hydroxyl radical (OH(•), guest molecule). From this analysis, two distinct steps were identified in the recognition process of hydroxyl radical by glutathione: catching and steering, based on the interactions between the host-guest molecules. Over 78% of all interactions are related to the catching mechanism via complex formation between anionic carboxyl groups and the OH radical, hence both terminal residues of GSH serve as recognition sites. The glycine residue has an additional role in the recognition of OH radical, namely the steering. The flexibility of the Gly residue enables the formation of further interactions of other parts of glutathione (e.g. thiol, α- and β-carbons) with the lone electron pair of the hydroxyl radical. Moreover, quantum chemical calculations were carried out on selected GSH/OH(•) complexes and on appropriate GSH conformers to describe the energy profile of the recognition process. The relative enthalpy and the free energy changes of the radical recognition of the strongest complexes varied from -42.4 to -27.8 kJ/mol and from -21.3 to 9.8 kJ/mol, respectively. These complexes, containing two or more intermolecular interactions, would be the starting configurations for the hydrogen atom migration to quench the hydroxyl radical via different reaction channels.

  5. Glutathione – Hydroxyl Radical Interaction: A Theoretical Study on Radical Recognition Process

    PubMed Central

    Fiser, Béla; Jójárt, Balázs; Csizmadia, Imre G.; Viskolcz, Béla

    2013-01-01

    Non-reactive, comparative (2×1.2 μs) molecular dynamics simulations were carried out to characterize the interactions between glutathione (GSH, host molecule) and hydroxyl radical (OH•, guest molecule). From this analysis, two distinct steps were identified in the recognition process of hydroxyl radical by glutathione: catching and steering, based on the interactions between the host-guest molecules. Over 78% of all interactions are related to the catching mechanism via complex formation between anionic carboxyl groups and the OH radical, hence both terminal residues of GSH serve as recognition sites. The glycine residue has an additional role in the recognition of OH radical, namely the steering. The flexibility of the Gly residue enables the formation of further interactions of other parts of glutathione (e.g. thiol, α- and β-carbons) with the lone electron pair of the hydroxyl radical. Moreover, quantum chemical calculations were carried out on selected GSH/OH• complexes and on appropriate GSH conformers to describe the energy profile of the recognition process. The relative enthalpy and the free energy changes of the radical recognition of the strongest complexes varied from −42.4 to −27.8 kJ/mol and from −21.3 to 9.8 kJ/mol, respectively. These complexes, containing two or more intermolecular interactions, would be the starting configurations for the hydrogen atom migration to quench the hydroxyl radical via different reaction channels. PMID:24040010

  6. Immunogenicity of mitochondrial DNA modified by hydroxyl radical.

    PubMed

    Alam, Khurshid; Moinuddin; Jabeen, Suraya

    2007-05-01

    Mitochondria consume about 90 percent of oxygen used by the body, and are a particularly rich source of reactive oxygen species (ROS). In this research communication mitochondrial DNA (mtDNA) was isolated from fresh goat liver and modified in vitro by hydroxyl radical generated from UV irradiation (254 nm) of hydrogen peroxide. As a consequence of hydroxyl radical modification, mtDNA showed hyperchromicity and sensitivity to nuclease S1 digestion as compared to control mtDNA. Animals immunized with mtDNA and ROS-modified mtDNA induced antibodies as detected by direct binding and competition ELISA. The data suggest that immunogenicity of mtDNA got augmented after treatment with hydroxyl radical. IgG isolated from immune sera showed specificity for respective immunogen and cross-reaction with other nucleic acids. Binding of induced antibodies with array of antigens clearly indicates their polyspecific nature. Moreover, the polyspecificity exhibited by induced antibodies is unique in view of similar multiple antigen binding properties of naturally occurring anti-DNA antibodies derived from SLE patients.

  7. Generation of hydroxyl radicals from metal-loaded humic acids

    SciTech Connect

    Paciolla, M.D.; Jansen, S.A.; Davies, G.

    1999-06-01

    Humic acids (HAs) are naturally occurring biopolymers that are ubiquitous in the environment. They are most commonly found in the soil, drinking water, and a variety of plants. Pharmacological and therapeutic studies involving humic acids have been reported to some extent. However, when certain transition metals are bound to humic acids, e.g., iron and copper, they can be harmful to biological organisms. For this study, humic acids were extracted from German, Irish, and New Hampshire soils that were selectively chosen because of their reich abundance in humic material. Each sample was treated at room temperature with 0.1 M ferric and cupric solutions for 48 h. The amount of iron and copper adsorbed by humic acid was accurately quantitated using atomic absorption spectroscopy. The authors further demonstrate that these metal-loaded humic acids can produce deleterious oxidizing species such as the hydroxyl radical (HO*) through the metal-driven Fenton reaction. Electron paramagnetic resonance (EPR) employing spin trapping techniques with 5,5-dimethylpyrroline N-oxide (DMPO) is used to confirm the generation of hydroxyl radicals. The DMPO-OH adduct with hyperfine splitting constants A{sub N} = A{sub H} = 14.9 G is observed upon the addition of exogenous hydrogen peroxide. The concentration of hydroxyl radical was determined using 4-hydroxytempo (TEMPO-OH) as a spin standard. The presence of another oxidizing species, Fe{double_bond}O{sup 2+}, is also proposed in the absence of hydrogen peroxide.

  8. Superb hydroxyl radical-mediated biocidal effect induced antibacterial activity of tuned ZnO/chitosan type II heterostructure under dark

    NASA Astrophysics Data System (ADS)

    Podder, Soumik; Halder, Suman; Roychowdhury, Anirban; Das, Dipankar; Ghosh, Chandan Kr.

    2016-10-01

    Reactive oxygen species (ROS) is the most dominating factor for bacteria cell toxicity due to release of oxidative stress. Hydroxyl radical (·OH) is a strong oxidizing ROS that has high impact on biocidal activity. This present paper highlights ·OH influenced antibacterial activity and biocidal propensity of tuned ZnO/chitosan (ZnO/CS) nanocomposite against Pseudomonas putida (P. putida) in the absence of light for the first time. For this purpose, the CS proportion was increased by 25 % (w/w) of ZnO during the preparation of ZnO/CS nanocomposite and a systematic study of different ROS like superoxide anion (O 2 ·- ), hydrogen peroxide (H2O2) and ·OH production as well as their kinetics was carried out both under UV irradiation and in dark by UV-Vis spectroscopy using NBT dye, starch and iodine reaction and fluorescence spectroscopy using terephthalic acid. The decoration of ZnO nanoparticles (ZnO·NPs) with CS tuning was characterized by XRD and FTIR spectroscopy, revealing sustained crystallinity and surface coating of ZnO NP (size about 24 nm) by CS molecule. The hybridization of ZnO nanoparticles with CS@50 wt% (w/w) resulted superior biocidal activity (81 %) within 3 h in dark mediated by optimum production of ·OH among all ROS. Here we have proposed the enhanced production of ·OH in ZnO/CS due to generation of holes by entrapment of electrons in acceptor level formed in nanocomposite for the first time, and the acceptor levels were probed by Positron annihilation lifetime spectroscopy. The increase in non-positronium (non-Ps) formation probability (I2) in ZnO/CS nanocomposite confirmed the acceptor levels. This work also confirms surface defect-mediated ROS generation in dark, and zinc interstitials are proposed as active defect sites for generation of holes and ·OH for the first time and confirmed by steady-state room temperature photoluminescence spectroscopy. Finally, a plausible mechanism was hypothesized focusing on hole generation in ZnO NP and

  9. Hydroxyl radical reaction with trans-resveratrol: initial carbon radical adduct formation followed by rearrangement to phenoxyl radical.

    PubMed

    Li, Dan-Dan; Han, Rui-Min; Liang, Ran; Chen, Chang-Hui; Lai, Wenzhen; Zhang, Jian-Ping; Skibsted, Leif H

    2012-06-21

    In the reaction between trans-resveratrol (resveratrol) and the hydroxyl radical, kinetic product control leads to a short-lived hydroxyl radical adduct with an absorption maximum at 420 nm and a lifetime of 0.21 ± 0.01 μs (anaerobic acetonitrile at 25 °C) as shown by laser flash photolysis using N-hydroxypyridine-2(1H)-thione (N-HPT) as a "photo-Fenton" reagent. The transient spectra of the radical adduct are in agreement with density functional theory (DFT) calculations showing an absorption maximum at 442 or 422 nm for C2 and C6 hydroxyl adducts, respectively, and showing the lowest energy for the transition state leading to the C2 adduct compared to other radical products. From this initial product, the relative long-lived 4'-phenoxyl radical of resveratrol (τ = 9.9 ± 0.9 μs) with an absorption maximum at 390 nm is formed in a process with a time constant (τ = 0.21 ± 0.01 μs) similar to the decay constant for the C2 hydroxyl adduct (or a C2/C6 hydroxyl adduct mixture) and in agreement with thermodynamics identifying this product as the most stable resveratrol radical. The hydroxyl radical adduct to phenoxyl radical conversion with concomitant water dissociation has a rate constant of 5 × 10(6) s(-1) and may occur by intramolecular hydrogen atom transfer or by stepwise proton-assisted electron transfer. Photolysis of N-HPT also leads to a thiyl radical which adds to resveratrol in a parallel reaction forming a sulfur radical adduct with a lifetime of 0.28 ± 0.04 μs and an absorption maximum at 483 nm.

  10. Structural Characterization of Hydroxyl Radical Adducts in Aqueous Media

    NASA Astrophysics Data System (ADS)

    Janik, Ireneusz; Tripathi, G. N. R.

    2015-06-01

    The oxidation by the hydroxyl (OH) radical is one of the most widely studied reactions because of its central role in chemistry, biology, organic synthesis, and photocatalysis in aqueous environments, wastewater treatment, and numerous other chemical processes. Although the redox potential of OH is very high, direct electron transfer (ET) is rarely observed. If it happens, it mostly proceeds through the formation of elusive OH adduct intermediate which facilitates ET and formation of hydroxide anion. Using time resolved resonance Raman technique we structurally characterized variety of OH adducts to sulfur containing organic compounds, halide ions as well as some metal cations. The bond between oxygen of OH radical and the atom of oxidized molecule differs depending on the nature of solute that OH radical reacts with. For most of sulfur containing organics, as well as halide and pseudo-halide ions, our observation suggested that this bond has two-center three-electron character. For several metal aqua ions studied, the nature of the bond depends on type of the cation being oxidized. Discussion on spectral parameters of all studied hydroxyl radical adducts as well as the role solvent plays in their stabilization will be presented.

  11. Methyl-esterified 3-hydroxybutyrate oligomers protect bacteria from hydroxyl radicals.

    PubMed

    Koskimäki, Janne J; Kajula, Marena; Hokkanen, Juho; Ihantola, Emmi-Leena; Kim, Jong H; Hautajärvi, Heidi; Hankala, Elina; Suokas, Marko; Pohjanen, Johanna; Podolich, Olga; Kozyrovska, Natalia; Turpeinen, Ari; Pääkkönen, Mirva; Mattila, Sampo; Campbell, Bruce C; Pirttilä, Anna Maria

    2016-05-01

    Bacteria rely mainly on enzymes, glutathione and other low-molecular weight thiols to overcome oxidative stress. However, hydroxyl radicals are the most cytotoxic reactive oxygen species, and no known enzymatic system exists for their detoxification. We now show that methyl-esterified dimers and trimers of 3-hydroxybutyrate (ME-3HB), produced by bacteria capable of polyhydroxybutyrate biosynthesis, have 3-fold greater hydroxyl radical-scavenging activity than glutathione and 11-fold higher activity than vitamin C or the monomer 3-hydroxybutyric acid. We found that ME-3HB oligomers protect hypersensitive yeast deletion mutants lacking oxidative stress-response genes from hydroxyl radical stress. Our results show that phaC and phaZ, encoding polymerase and depolymerase, respectively, are activated and polyhydroxybutyrate reserves are degraded for production of ME-3HB oligomers in bacteria infecting plant cells and exposed to hydroxyl radical stress. We found that ME-3HB oligomer production is widespread, especially in bacteria adapted to stressful environments. We discuss how ME-3HB oligomers could provide opportunities for numerous applications in human health.

  12. Generation of hydroxyl radicals during ascites experimentally induced in broilers.

    PubMed

    Arab, H A; Jamshidi, R; Rassouli, A; Shams, G; Hassanzadeh, M H

    2006-04-01

    Increased metabolic rates, pulmonary hypertension and cardiac dysfunction are the most important features of the ascites syndrome in broiler chickens. However, the mechanism of cell injury causing the pathogenesis of the syndrome is not clearly understood. Our study aimed to examine the generation of hydroxyl radicals (OH*) in broiler chickens experiencing ascites. The hundred and fifty 1-d-old chickens were purchased from a local hatchery and reared in an open poultry house for 46 d. They were divided at random into three groups and ascites was induced in two groups by exposing them to low temperature or administration of triiodothyronine (T(3)). The third group served as control and was reared normally. Haematological, biochemical and pathological tests were used to determine the incidence of ascites: including total red blood cell (RBC), packed cell volume (PCV), release of alanine transaminase (ALT) and aspartate transaminase (AST) and ratio of right ventricular weight to total ventricular weight (RV/TV). A salicylate hydroxylation method was used to examine the generation of hydroxyl radicals (OH*) in treated groups. TWo hydroxylated salicylic acid metabolites, 2,3- and 2,5-dihydroxy benzoic acid (2,3- and 2,5-DHBA), were measured by HPLC to detect the generation of OH*. An ascites syndrome was observed in T(3) and low-temperature treated groups, as shown by necropsy changes and increases in f RBC, PCV, ALT, AST and the ratio of RV/TV. Concentrations of 2,3- and 2,5-DHBA were increased in groups experiencing ascites compared to control group. It is suggested that reactive oxygen species that is OH* ions, may be involved in the pathogenesis of the ascites syndrome in broiler chickens.

  13. Synthesis and antioxidant capacities of hydroxyl derivatives of cinnamoylphenethylamine in protecting DNA and scavenging radicals.

    PubMed

    Yang, Yang; Song, Zhi-Guang; Liu, Zai-Qun

    2011-04-01

    Cinnamoylphenethylamine (CNPA) derivatives including feruloylphenethylamine (FRPA), caffeoylphenethylamine (CFPA), cinnamoyltyramine (CNTA), feruloyltyramine (FRTA) and caffeoyltyramine (CFTA) were synthesized in order to investigate the influence of the number and position of hydroxyl group on Cu(2+)/glutathione (GSH) and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidation of DNA. The radical-scavenging properties of these CNPA derivatives were also evaluated by trapping 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonate) cationic radical (ABTS(+•)), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH) and galvinoxyl radical. In addition, these CNPA derivatives were tested by linoleic acid (LH)-β-carotene-bleaching experiment. The chemical kinetic was employed to treat the results from AAPH-induced oxidation of DNA and gave the order of antioxidant ability as CFTA > CFPA > FRTA > FRPA. CFTA and CFPA also possessed high abilities to inhibit Cu²(+)/GSH-mediated degradation of DNA, whereas FRPA and FRTA can protect LH against the auto-oxidation efficiently. Finally, CFPA and FRPA exhibited high activity in trapping ABTS(+•), DPPH and galvinoxyl radicals. Therefore, the cinnamoyl group bearing ortho-dihydroxyl or hydroxyl with ortho-methoxyl benefited for CNPA derivatives to protect DNA, while hydroxyl in tyramine cannot enhance the radical-scavenging abilities of CNPA derivatives.

  14. Future Directions of Structural Mass Spectrometry using Hydroxyl Radical Footprinting

    SciTech Connect

    J Kiselar; M Chance

    2011-12-31

    Hydroxyl radical protein footprinting coupled to mass spectrometry has been developed over the last decade and has matured to a powerful method for analyzing protein structure and dynamics. It has been successfully applied in the analysis of protein structure, protein folding, protein dynamics, and protein-protein and protein-DNA interactions. Using synchrotron radiolysis, exposure of proteins to a 'white' X-ray beam for milliseconds provides sufficient oxidative modification to surface amino acid side chains, which can be easily detected and quantified by mass spectrometry. Thus, conformational changes in proteins or protein complexes can be examined using a time-resolved approach, which would be a valuable method for the study of macromolecular dynamics. In this review, we describe a new application of hydroxyl radical protein footprinting to probe the time evolution of the calcium-dependent conformational changes of gelsolin on the millisecond timescale. The data suggest a cooperative transition as multiple sites in different molecular subdomains have similar rates of conformational change. These findings demonstrate that time-resolved protein footprinting is suitable for studies of protein dynamics that occur over periods ranging from milliseconds to seconds. In this review, we also show how the structural resolution and sensitivity of the technology can be improved as well. The hydroxyl radical varies in its reactivity to different side chains by over two orders of magnitude, thus oxidation of amino acid side chains of lower reactivity are more rarely observed in such experiments. Here we demonstrate that the selected reaction monitoring (SRM)-based method can be utilized for quantification of oxidized species, improving the signal-to-noise ratio. This expansion of the set of oxidized residues of lower reactivity will improve the overall structural resolution of the technique. This approach is also suggested as a basis for developing hypothesis

  15. [Effects of hydroxyl radicals on purified angiotensin I converting enzyme].

    PubMed

    Michel, B; Nirina, L B; Grima, M; Ingert, C; Coquard, C; Barthelmebs, M; Imbs, J L

    1998-08-01

    Somatic angiotensin-converting enzyme (ACE) is a protein which contains two similar domains (N and C), each possessing a functional active site. The relationship between ACE, its natural substrates and oxygen free radicals is starting to be explored. On one hand, superoxide anions production is induced by angiotensin II and on the other hand, activated polynuclear neutrophils, through free radicals generation, alter endothelial ACE activity. In this study, we examined the impact of hydroxyl radicals (.OH) on purified ACE. .OH were produced using a generator: 2,2'-azo-bis 2-amidinopropane (GRH) provided by Lara-Spiral (Fr). GRH (3 mM), in a time-dependent fashion, inhibited ACE activity. When ACE was co-incubated for 4 h with GRH, its activity decreased by 70%. Addition of dimethylthiourea (DMTU: 0.03 to 1 mM) or mannitol + methionine (20/10 mM), two sets of .OH scavengers, produced a dose-dependent protection on ACE activity. To examine whether oxidation of thiol groups in the ACE molecule could be involved in the action of GRH, the effects of thiol reducing agents: mercaptoethanol and dithiotreitol (DTT) were investigated. These compounds produced a dose-dependent and significant protection; with 100% protection at 0.2 and 0.3 mM for mercaptoethanol and at 0.1 mM for DTT. The hydrolysis of two natural and domain-specific substrates were also explored. The hydrolysis of angiotensin I preferentially cleaved by the C domain was significantly (p < 0.01) inhibited by 57, 58 and 69% in contact with 0.3, 1 and 3 mM GRH [in nmol angio II formed/min/nmol of ACE, n = 4; 35.9 +/- 0.6 (control), 15.5 +/- 2.8 (GRH : 0.3 mM), 15.1 +/- 0.5 (1), 10.9 +/- 0.6 (3)]. The hydrolysis of the hemoregulatory peptide (hp), preferential substrate for the N domain was not affected by GRH at 0.3 mM and inhibited by 28% (not significant) by 1 mM GRH [in nmol ph hydrolized/min/nmol ACE, n = 4; 12.6 +/- 1.9 (control), 14.9 (GRH : 0.3 mM), 8.3 +/- 4.0 (1). These results demonstrated that .OH

  16. Quantum Chemical Study on the Antioxidation Mechanism of Piceatannol and Isorhapontigenin toward Hydroxyl and Hydroperoxyl Radicals

    PubMed Central

    Lu, Yang; Wang, AiHua; Shi, Peng; Zhang, Hui; Li, ZeSheng

    2015-01-01

    A systematic study of the antioxidation mechanisms behind hydroxyl (•OH) and hydroperoxyl (•OOH) radical scavenging activity of piceatannol (PIC) and isorhapontigenin (ISO) was carried out using density functional theory (DFT) method. Two reaction mechanisms, abstraction (ABS) and radical adduct formation (RAF), were discussed. A total of 24 reaction pathways of scavenging •OH and •OOH with PIC and ISO were investigated in the gas phase and solution. The thermodynamic and kinetic properties of all pathways were calculated. Based on these results, we evaluated the antioxidant activity of every active site of PIC and ISO and compared the abilities of PIC and ISO to scavenge radicals. According to our results, PIC and ISO may act as effective •OH and •OOH scavengers in organism. A4-hydroxyl group is a very important active site for PIC and ISO to scavenge radicals. The introducing of -OH or -OCH3 group to the ortho-position of A4-hydroxyl group would increase its antioxidant activity. Meanwhile, the conformational effect was researched, the results suggest that the presence and pattern of intramolecular hydrogen bond (IHB) are considerable in determining the antioxidant activity of PIC and ISO. PMID:26176778

  17. Ultraviolet irradiation-induced substitution of fluorine with hydroxyl radical for mass spectrometric analysis of perfluorooctane sulfonyl fluoride.

    PubMed

    Wang, Peng; Tang, Xuemei; Huang, Lulu; Kang, Jie; Zhong, Hongying

    2016-01-28

    A rapid and solvent free substitution reaction of a fluorine atom in perfluorooctane sulfonyl fluoride (PFOSF) with a hydroxyl radical is reported. Under irradiation of ultraviolet laser on semiconductor nanoparticles or metal surfaces, hydroxyl radicals can be generated through hole oxidization. Among all fluorine atoms of PFOSF, highly active hydroxyl radicals specifically substitute the fluorine of sulfonyl fluoride functional group. Resultant perfluorooctane sulfonic acid is further ionized through capture of photo-generated electrons that switch the neutral molecules to negatively charged odd electron hypervalent ions. The unpaired electron subsequently initiates α O-H bond cleavage and produces perfluorooctane sulfonate negative ions. Hydroxyl radical substitution and molecular dissociation of PFOSF have been confirmed by masses with high accuracy and resolution. It has been applied to direct mass spectrometric imaging of PFOSF adsorbed on surfaces of plant leaves.

  18. Iron reduction potentiates hydroxyl radical formation only in flavonols.

    PubMed

    Macáková, Kateřina; Mladěnka, Přemysl; Filipský, Tomáš; Říha, Michal; Jahodář, Luděk; Trejtnar, František; Bovicelli, Paolo; Proietti Silvestri, Ilaria; Hrdina, Radomír; Saso, Luciano

    2012-12-15

    Flavonoids, substantial components of the human diet, are generally considered to be beneficial. However, they may possess possible pro-oxidative effects, which could be based on their reducing potential. The aims of this study were to evaluate the ability of 26 flavonoids to reduce ferric ions at relevant pH conditions and to find a possible relationship with potentiation of hydroxyl radical production. A substantial ferric ions reduction was achieved under acidic conditions, particularly by flavonols and flavanols with the catecholic ring B. Apparently corresponding bell-shaped curves displaying the pro-oxidant effect of flavonols quercetin and kaempferol on iron-based Fenton reaction were documented. Several flavonoids were efficient antioxidants at very low concentrations but rather inefficient or pro-oxidative at higher concentrations. Flavonols, morin and rutin were progressively pro-oxidant, while 7-hydroxyflavone and hesperetin were the only flavonoids with dose-dependent inhibition of hydroxyl radical production. Conclusively, administration of flavonoids may lead to unpredictable consequences with few exceptions.

  19. Hydroxyl radical generation by a light-dependent Fenton reaction.

    PubMed

    Van der Zee, J; Krootjes, B B; Chignell, C F; Dubbelman, T M; Van Steveninck, J

    1993-02-01

    Illumination of Fe3+, with light of a wavelength varying from 250 to 450 nm, in the presence of the iron chelators ethylenediamine N,N,N',N'-tetraacetic acid (EDTA), ethyleneglycol-bis-(beta-aminoethylether)N,N,N',N'-tetraacet ic acid (EGTA), diethylenetriamine-N,N,N',N',N'-pentaacetic acid (DTPA), or citrate resulted in the reduction of Fe3+ to Fe2+. Fe2+ formation was measured by the formation of its complex with bathophenanthroline disulfonic acid. In all cases Fe2+ formation was completely dependent on the presence of the iron chelator and on the wavelength used for illumination. A correlation was found between the absorption spectrum of the iron-chelator complex and the amount of Fe3+ reduced, suggesting that the absorption of light induced an electron transfer from the chelator to the iron ion. Exposure to oxygen, either during or after illumination, resulted in degradation of the chelator molecule. Illumination of the Fe(3+)-chelator complexes in the presence of H2O2 resulted in the formation of hydroxyl radicals, which could be determined by the formation of the 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-hydroxyl radical adduct, using electron spin resonance spectroscopy. Formation of the spin adduct was inhibited by addition of catalase, mannitol, ethanol, or formate, whereas superoxide dismutase had no effect.

  20. Role of the hydroxyl radical in soot formation

    NASA Technical Reports Server (NTRS)

    King, Galen B.; Laurendeau, Normand M.

    1983-01-01

    The goal of this project is to determine the role of the hydroxyl radical during formation of soot. Correlations will be sought between OH concentration and (1) the critical equivalence ratio for incipient soot formation and (2) soot yield as a function of higher equivalence ratios. The ultimate aim is the development of a quasi-global kinetic model for the pre-particulate chemistry leading to soot nucleation. Hydroxyl radical concentration profiles are measured directly in both laminar premixed and diffusion flames using the newly developed technique, laser saturated fluorescence (LSF). This method is capable of measuring OH in the presence of soot particles. Aliphatic and aromatic fuels will be used to assess the influence of fuel type on soot formation. The influence of flame temperature on the critical equivalence ratio and soot yield will be related to changes in the OH concentration profiles. LSF measurements will be augmented with auxiliary measurements of soot and PAH concentrations to allow the development of a quasi-global model for soot formation.

  1. Unexpectedly high indoor hydroxyl radical concentrations associated with nitrous acid.

    PubMed

    Gómez Alvarez, Elena; Amedro, Damien; Afif, Charbel; Gligorovski, Sasho; Schoemaecker, Coralie; Schoemacker, Coralie; Fittschen, Christa; Doussin, Jean-Francois; Wortham, Henri

    2013-08-13

    The hydroxyl (OH) radical is the most important oxidant in the atmosphere since it controls its self-oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been ignored up to now. In the indoor air, the ozonolysis of alkenes has been suggested as an alternative route of OH formation. Models and indirect measurements performed up to now according to this hypothesis suggest concentrations of OH radicals on the order of 10(4)-10(5) molecules per cubic centimeter. Here, we present direct measurements of significant amounts of OH radicals of up to 1.8⋅10(6) molecules per cubic centimeter during an experimental campaign carried out in a school classroom in Marseille. This concentration is on the same order of magnitude of outdoor OH levels in the urban scenario. We also show that photolysis of HONO is an important source of OH radicals indoors under certain conditions (i.e., direct solar irradiation inside the room). Additionally, the OH concentrations were found to follow a linear dependence with the product J(HONO)⋅[HONO]. This was also supported by using a simple quasiphotostationary state model on the OH radical budget. These findings force a change in our understanding of indoor air quality because the reactivity linked to OH would involve formation of secondary species through chemical reactions that are potentially more hazardous than the primary pollutants in the indoor air.

  2. Unexpectedly high indoor hydroxyl radical concentrations associated with nitrous acid

    PubMed Central

    Gómez Alvarez, Elena; Amedro, Damien; Afif, Charbel; Gligorovski, Sasho; Schoemaecker, Coralie; Fittschen, Christa; Doussin, Jean-Francois; Wortham, Henri

    2013-01-01

    The hydroxyl (OH) radical is the most important oxidant in the atmosphere since it controls its self-oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been ignored up to now. In the indoor air, the ozonolysis of alkenes has been suggested as an alternative route of OH formation. Models and indirect measurements performed up to now according to this hypothesis suggest concentrations of OH radicals on the order of 104–105 molecules per cubic centimeter. Here, we present direct measurements of significant amounts of OH radicals of up to 1.8⋅106 molecules per cubic centimeter during an experimental campaign carried out in a school classroom in Marseille. This concentration is on the same order of magnitude of outdoor OH levels in the urban scenario. We also show that photolysis of HONO is an important source of OH radicals indoors under certain conditions (i.e., direct solar irradiation inside the room). Additionally, the OH concentrations were found to follow a linear dependence with the product J(HONO)⋅[HONO]. This was also supported by using a simple quasiphotostationary state model on the OH radical budget. These findings force a change in our understanding of indoor air quality because the reactivity linked to OH would involve formation of secondary species through chemical reactions that are potentially more hazardous than the primary pollutants in the indoor air. PMID:23898188

  3. Hydroxyl radicals form in natural sediments - effects on sedimentary organic matter

    NASA Astrophysics Data System (ADS)

    Skoog, Annelie; Alejandro Arias-Esquivel, Victor

    2010-05-01

    We show that hydroxyl radicals form at the oxic anoxic interface in marine sediments from ferrous iron reacting with hydrogen peroxide in the Fenton reaction. The aggressive nature of hydroxyl radicals makes it likely that they participate in degradation of sedimentary organic matter (SOM). We used terephthalic acid (TPA) to trap the hydroxyl radicals in sediment cores - TPA reacts with hydroxyl radicals to form the highly fluorescent product TPAOH. Results indicated formation of TPAOH at high concentrations at the oxic-anoxic interface. We also subjected SOM to hydroxyl radicals formed by the Fenton reaction, which resulted in changes in fluorescence properties and chemical composition. This is the first study showing formation of hydroxyl radicals and their effect on SOM, which is a previously unknown mechanism in the global carbon cycle.

  4. Environmentally Persistent Free Radicals (EPFRs). 3. Free versus Bound Hydroxyl Radicals in EPFR Aqueous Solutions

    PubMed Central

    2015-01-01

    Additional experimental evidence is presented for in vitro generation of hydroxyl radicals because of redox cycling of environmentally persistent free radicals (EPFRs) produced after adsorption of 2-monochlorophenol at 230 °C (2-MCP-230) on copper oxide supported by silica, 5% Cu(II)O/silica (3.9% Cu). A chemical spin trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed. Experiments in spiked O17 water have shown that ∼15% of hydroxyl radicals formed as a result of redox cycling. This amount of hydroxyl radicals arises from an exogenous Fenton reaction and may stay either partially trapped on the surface of particulate matter (physisorbed or chemisorbed) or transferred into solution as free OH. Computational work confirms the highly stable nature of the DMPO–OH adduct, as an intermediate produced by interaction of DMPO with physisorbed/chemisorbed OH (at the interface of solid catalyst/solution). All reaction pathways have been supported by ab initio calculations. PMID:25036238

  5. Reactivity of aqueous phase hydroxyl radical with halogenated carboxylate anions: experimental and theoretical studies.

    PubMed

    Minakata, Daisuke; Song, Weihua; Crittenden, John

    2011-07-15

    With concerns about emerging contaminants increasing, advanced oxidation processes have become attractive technologies because of potential mineralization of these contaminants via radical involved reactions that are induced by highly reactive hydroxyl radical. Considering the expensive and time-consuming experimental studies of degradation intermediates and byproduct, there is a need to develop a first-principles computer-based kinetic model that predict reaction pathways and associated reaction rate constants. In this study, we measured temperature-dependent hydroxyl radical reaction rate constants for a series of haloacetate ions and obtained their Arrhenius kinetic parameters. We found a linear correlation between these reaction rate constants and theoretically calculated aqueous-phase free energies of activation. To understand the quantitative effects on entropy of solvation due to solvent water molecules, we calculate each portion of the entropic energies that contribute to the overall aqueous phase entropy of activation; cavity formation is a dominant portion. For the series of reactions of hydroxyl radical with carboxylate ions, the increase in the entropy of activation during the solvation process is approximately 10-15 cal mol(-1)K(-1) because of interactions with solvent water molecules and the transition state. Finally, charge distribution analysis for the aqueous-phase reactions of hydroxyl radical with acetate/haloacetate ions reveals that in the aqueous phase, the degree of polarizability at the transition state is less substantial than those that are in the gaseous phase resulting in a high charge density. In the presence of electronegative halogenated functional groups, the transition state is less polarized and hydrogen bonding interactions are expected to be weaker.

  6. L-carnosine (beta-alanyl-L-histidine) and carcinine (beta-alanylhistamine) act as natural antioxidants with hydroxyl-radical-scavenging and lipid-peroxidase activities.

    PubMed Central

    Babizhayev, M A; Seguin, M C; Gueyne, J; Evstigneeva, R P; Ageyeva, E A; Zheltukhina, G A

    1994-01-01

    Carnosine (beta-alanyl-L-histidine) and carcinine (beta-alanylhistamine) are natural imidazole-containing compounds found in the non-protein fraction of mammalian tissues. Carcinine was synthesized by an original procedure and characterized. Both carnosine and carcinine (10-25 mM) are capable of inhibiting the catalysis of linoleic acid and phosphatidylcholine liposomal peroxidation (LPO) by the O2(-.)-dependent iron-ascorbate and lipid-peroxyl-radical-generating linoleic acid 13-monohydroperoxide (LOOH)-activated haemoglobin systems, as measured by thiobarbituric-acid-reactive substance. Carcinine and carnosine are good scavengers of OH. radicals, as detected by iron-dependent radical damage to the sugar deoxyribose. This suggests that carnosine and carcinine are able to scavenge free radicals or donate hydrogen ions. The iodometric, conjugated diene and t.l.c. assessments of lipid hydroperoxides (13-monohydroperoxide linoleic acid and phosphatidylcholine hydroperoxide) showed their efficient reduction and deactivation by carnosine and carcinine (10-25 mM) in the liberated and bound-to-artificial-bilayer states. This suggests that the peroxidase activity exceeded that susceptible to direct reduction with glutathione peroxidase. Imidazole, solutions of beta-alanine, or their mixtures with peptide moieties did not show antioxidant potential. Free L-histidine and especially histamine stimulated iron (II) salt-dependent LPO. Due to the combination of weak metal chelating (abolished by EDTA), OH. and lipid peroxyl radicals scavenging, reducing activities to liberated fatty acid and phospholipid hydroperoxides, carnosine and carcinine appear to be physiological antioxidants able to efficiently protect the lipid phase of biological membranes and aqueous environments. PMID:7998987

  7. Spectroscopy and reaction dynamics of collision complexes containing hydroxyl radicals

    SciTech Connect

    Lester, M.I.

    1993-12-01

    The DOE supported work in this laboratory has focused on the spectroscopic characterization of the interaction potential between an argon atom and a hydroxyl radical in the ground X{sup 2}II and excited A {sup 2}{summation}{sup +} electronic states. The OH-Ar system has proven to be a test case for examining the interaction potential in an open-shell system since it is amenable to experimental investigation and theoretically tractable from first principles. Experimental identification of the bound states supported by the Ar + OH (X {sup 2}II) and Ar + OH(A {sup 2}{summation}{sup +}) potentials makes it feasible to derive realistic potential energy surfaces for these systems. The experimentally derived intermolecular potentials provide a rigorous test of ab initio theory and a basis for understanding the dramatically different collision dynamics taking place on the ground and excited electronic state surfaces.

  8. Perinatal manganese exposure and hydroxyl radical formation in rat brain.

    PubMed

    Bałasz, Michał; Szkilnik, Ryszard; Brus, Ryszard; Malinowska-Borowska, Jolanta; Kasperczyk, Sławomir; Nowak, Damian; Kostrzewa, Richard M; Nowak, Przemysław

    2015-01-01

    The present study was designed to investigate the role of pre- and postnatal manganese (Mn) exposure on hydroxyl radical (HO(•)) formation in the brains of dopamine (DA) partially denervated rats (Parkinsonian rats). Wistar rats were given tap water containing 10,000 ppm manganese chloride during the duration of pregnancy and until the time of weaning. Control rat dams consumed tap water without added Mn. Three days after birth, rats of both groups were treated with 6-hydroxydopamine at one of three doses (15, 30, or 67 µg, intraventricular on each side), or saline vehicle. We found that Mn content in the brain, kidney, liver, and bone was significantly elevated in dams exposed to Mn during pregnancy. In neonates, the major organs that accumulated Mn were the femoral bone and liver. However, Mn was not elevated in tissues in adulthood. To determine the possible effect on generation of the reactive species, HO(•) in Mn-induced neurotoxicity, we analyzed the contents of 2.3- and 2.5-dihydroxybenzoic acid (spin trap products of salicylate; HO(•) being an index of in vivo HO(•) generation), as well as antioxidant enzyme activities of superoxide dismutase (SOD) isoenzymes and glutathione S-transferase (GST). 6-OHDA-depletion of DA produced enhanced HO(•) formation in the brain tissue of newborn and adulthood rats that had been exposed to Mn, and the latter effect did not depend on the extent of DA denervation. Additionally, the extraneuronal, microdialysate, content of HO(•) in neostriatum was likewise elevated in 6-OHDA-lesioned rats. Interestingly, there was no difference in extraneuronal HO(•) formation in the neostriatum of Mn-exposed versus control rats. In summary, findings in this study indicate that Mn crosses the placenta but in contrast to other heavy metals, Mn is not deposited long term in tissues. Also, damage to the dopaminergic system acts as a "trigger mechanism," initiating a cascade of adverse events leading to a protracted increase in

  9. Hydroxylated chalcones with dual properties: xanthine oxidase inhibitors and radical scavengers

    PubMed Central

    Hofmann, Emily; Webster, Jonathan; Do, Thuy; Kline, Reid; Snider, Lindsey; Hauser, Quintin; Higginbottom, Grace; Campbell, Austin; Ma, Lili; Paula, Stefan

    2016-01-01

    In this study, we evaluated the abilities of a series of chalcones to inhibit the activity of the enzyme xanthine oxidase (XO) and to scavenge radicals. 20 mono- and polyhydroxylated chalcone derivatives were synthesized by Claisen-Schmidt condensation reactions and then tested for inhibitory potency against XO, a known generator of reactive oxygen species (ROS). In parallel, the ability of the synthesized chalcones to scavenge a stable radical was determined. Structure-activity relationship analysis in conjunction with molecular docking indicated that the most active XO inhibitors carried a minimum of three hydroxyl groups. Moreover, the most effective radical scavengers had two neighboring hydroxyl groups on at least one of the two phenyl rings. Since it has been proposed previously that XO inhibition and radical scavenging could be useful properties for reduction of ROS-levels in tissue, we determined the chalcones’ effects to rescue neurons subjected to ROS-induced stress created by the addition of β-amyloid peptide. Best protection was provided by chalcones that combined good inhibitory potency with high radical scavenging ability in a single molecule, an observation that points to a potential therapeutic value of this compound class. PMID:26762836

  10. Hydroxylated chalcones with dual properties: Xanthine oxidase inhibitors and radical scavengers.

    PubMed

    Hofmann, Emily; Webster, Jonathan; Do, Thuy; Kline, Reid; Snider, Lindsey; Hauser, Quintin; Higginbottom, Grace; Campbell, Austin; Ma, Lili; Paula, Stefan

    2016-02-15

    In this study, we evaluated the abilities of a series of chalcones to inhibit the activity of the enzyme xanthine oxidase (XO) and to scavenge radicals. 20 mono- and polyhydroxylated chalcone derivatives were synthesized by Claisen-Schmidt condensation reactions and then tested for inhibitory potency against XO, a known generator of reactive oxygen species (ROS). In parallel, the ability of the synthesized chalcones to scavenge a stable radical was determined. Structure-activity relationship analysis in conjunction with molecular docking indicated that the most active XO inhibitors carried a minimum of three hydroxyl groups. Moreover, the most effective radical scavengers had two neighboring hydroxyl groups on at least one of the two phenyl rings. Since it has been proposed previously that XO inhibition and radical scavenging could be useful properties for reduction of ROS-levels in tissue, we determined the chalcones' effects to rescue neurons subjected to ROS-induced stress created by the addition of β-amyloid peptide. Best protection was provided by chalcones that combined good inhibitory potency with high radical scavenging ability in a single molecule, an observation that points to a potential therapeutic value of this compound class.

  11. In vitro effect of H2O 2, some transition metals and hydroxyl radical produced via fenton and fenton-like reactions, on the catalytic activity of AChE and the hydrolysis of ACh.

    PubMed

    Méndez-Garrido, Armando; Hernández-Rodríguez, Maricarmen; Zamorano-Ulloa, Rafael; Correa-Basurto, José; Mendieta-Wejebe, Jessica Elena; Ramírez-Rosales, Daniel; Rosales-Hernández, Martha Cecilia

    2014-11-01

    It is well known that the principal biomolecules involved in Alzheimer's disease (AD) are acetylcholinesterase (AChE), acetylcholine (ACh) and the amyloid beta peptide of 42 amino acid residues (Aβ42). ACh plays an important role in human memory and learning, but it is susceptible to hydrolysis by AChE, while the aggregation of Aβ42 forms oligomers and fibrils, which form senile plaques in the brain. The Aβ42 oligomers are able to produce hydrogen peroxide (H2O2), which reacts with metals (Fe(2+), Cu(2+), Cr(3+), Zn(2+), and Cd(2+)) present at high concentrations in the brain of AD patients, generating the hydroxyl radical ((·)OH) via Fenton (FR) and Fenton-like (FLR) reactions. This mechanism generates high levels of free radicals and, hence, oxidative stress, which has been correlated with the generation and progression of AD. Therefore, we have studied in vitro how AChE catalytic activity and ACh levels are affected by the presence of metals (Fe(3+), Cu(2+), Cr(3+), Zn(2+), and Cd(2+)), H2O2 (without Aβ42), and (·) OH radicals produced from FR and FLR. The results showed that the H2O2 and the metals do not modify the AChE catalytic activity, but the (·)OH radical causes a decrease in it. On the other hand, metals, H2O2 and (·)OH radicals, increase the ACh hydrolysis. This finding suggests that when H2O2, the metals and the (·)OH radicals are present, both, the AChE catalytic activity and ACh levels diminish. Furthermore, in the future it may be interesting to study whether these effects are observed when H2O2 is produced directly from Aβ42.

  12. Comparison of fluorescence-based techniques for the quantification of particle-induced hydroxyl radicals

    PubMed Central

    Cohn, Corey A; Simon, Sanford R; Schoonen, Martin AA

    2008-01-01

    Background Reactive oxygen species including hydroxyl radicals can cause oxidative stress and mutations. Inhaled particulate matter can trigger formation of hydroxyl radicals, which have been implicated as one of the causes of particulate-induced lung disease. The extreme reactivity of hydroxyl radicals presents challenges to their detection and quantification. Here, three fluorescein derivatives [aminophenyl fluorescamine (APF), amplex ultrared, and dichlorofluorescein (DCFH)] and two radical species, proxyl fluorescamine and tempo-9-ac have been compared for their usefulness to measure hydroxyl radicals generated in two different systems: a solution containing ferrous iron and a suspension of pyrite particles. Results APF, amplex ultrared, and DCFH react similarly to the presence of hydroxyl radicals. Proxyl fluorescamine and tempo-9-ac do not react with hydroxyl radicals directly, which reduces their sensitivity. Since both DCFH and amplex ultrared will react with reactive oxygen species other than hydroxyl radicals and another highly reactive species, peroxynitite, they lack specificity. Conclusion The most useful probe evaluated here for hydroxyl radicals formed from cell-free particle suspensions is APF due to its sensitivity and selectivity. PMID:18307787

  13. Scavenging of hydroxyl radicals generated in human plasma following X-ray irradiation.

    PubMed

    Hosokawa, Yoichiro; Sano, Tomoaki

    2015-11-01

    There are various antioxidant materials that scavenge free radicals in human plasma. It is possible that the radical-scavenging function causes a radiation protective effect in humans. This study estimated the hydroxyl (OH) radical-scavenging activity induced by X-ray irradiation in human plasma. The test subjects included 111 volunteers (75 males and 36 females) ranging from 22 to 35 years old (average, 24.0). OH radicals generated in irradiated human plasma were measured by electron spin resonance (ESR). The relationships between the amount of the OH radical and chemical and biological parameters [total protein, total cholesterol, triglycerides and hepatitis B surface (HBs) antibodies] were estimated in the plasma of the 111 volunteers by a multivariate analysis. The presence of HBs antibodies had the greatest influence on OH radical-scavenging activity. One volunteer who did not have the HBs antibody was given an inoculation of the hepatitis B vaccine. There was a remarkable decrease in the amount of OH radical generated from plasma after the HBs antibody was produced. The results indicate that the HBs antibody is an important factor for the scavenging of OH radicals initiated by X-ray irradiation in the human body.

  14. Demonstration of hydroxyl radical generation in stunned' myocardium of intact dogs using aromatic hydroxylation of phenylalanine

    SciTech Connect

    Bolli, R.; Kaur, H.; Li, X.Y.; Triana, J.F.; Halliwell, B. Univ. of California, Davis King's College, London )

    1991-03-11

    Numerous studies have shown that postischemic myocardial dysfunction is attenuated by scavengers of hydroxyl ({sup {sm bullet}}OH) radicals and by iron chelators, suggesting an important pathogenetic role of {sup {sm bullet}}OH. However, the evidence provided by these studies is indirect. Since phenyl-alanine (PH) has been shown to react with {sup {sm bullet}}OH to form o-, m-, and p-tyrosines (TYR), the authors used aromatic hydroxylation of PH to detect {sup {sm bullet}}OH in stunned myocardium. Open-chest dogs underwent a 15-min coronary occlusion (O) followed by reperfusion (R). PH was infused i.v. starting 5 min pre-O and ending 10 min after R (n = 3) or starting at R and ending 10 min later (n = 8). TYR concentration in local coronary venous effluent plasma was measured using HPLC with electrochemical detection. No appreciable production of TYR was observed before or during O. After R, however, in all dogs there was a dramatic increase in myocardial production of o-, m-, and p-TYR which peaked at 1-3 min and ceased after 10 min. In 5 control dogs, infusion of PH without O/R did not result in any TYR production. These results provide evidence that the highly reactive {sup {sm bullet}}OH radical is produced after brief regional ischemia in the intact animal and indicate that PH may be a useful probe for measuring this species. The findings support the hypothesis that {sup {sm bullet}}OH contributes to myocardial stunning.'

  15. Oxidation of acetovanillone by photochemical processes and hydroxyl radicals.

    PubMed

    Benitez, F Javier; Real, Francisco J; Acero, Juan L; Leal, Ana I; Cotilla, Sonia

    2005-01-01

    Acetovanillone [Ethanone, 1-(4-hydroxy-3-metoxyphenyl)] is one of the major pollutants that is present in the wastewater produced during the boiling of raw material in the cork industry. The oxidation of its aqueous solutions by monochromatic UV radiation alone and combined with hydrogen peroxide, Fenton's reagent and the photo-Fenton system has been investigated. In the single UV radiation process, the apparent rate constants and the quantum yields are determined, and in the UV/H2O2 combination, the additional efficiency in the oxidation process due to the presence of hydrogen peroxide is established. The influence of some operating variables, such as initial concentrations of H2O2 and Fe(II), as well as the pH, is discussed in the Fenton and photo-Fenton systems, and the partial contribution of the radical pathways to the global oxidation rates are evaluated. The rate constant for the reaction of acetovanillone with hydroxyl radicals is also determined by means of a competition kinetics model, its value being 5.62 x 10(9) M(-1)s(-1). Finally, chemical oxidation experiments of wastewaters generated in this industry were carried out by using the same advanced oxidation processes. Specifically, the elimination of acetovanillone in these effluents was determined, and the removal of the global organic pollutant content was also evaluated.

  16. A pro-chelator triggered by hydrogen peroxide inhibits iron-promoted hydroxyl radical formation.

    PubMed

    Charkoudian, Louise K; Pham, David M; Franz, Katherine J

    2006-09-27

    The synthesis and structural characterization of a new pro-chelating agent, isonicotinic acid [2-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-benzylidene]-hydrazide (BSIH), are presented. BSIH only weakly interacts with iron unless hydrogen peroxide (H2O2) is present to remove the boronic ester protecting group to reveal a phenol that is a key metal-binding group of tridentate salicylaldehyde isonicotinoyl hydrazone (SIH). BSIH prevents deoxyribose degradation caused by hydroxyl radicals that are generated from H2O2 and redox-active iron by sequestering Fe3+ and preventing iron-promoted hydroxyl radical formation. The rate-determining step for iron sequestration is conversion of BSIH to SIH, followed by rapid Fe3+ complexation. The pro-chelate approach of BSIH represents a promising strategy for chelating a specific pool of detrimental metal ions without disturbing healthy metal ion distribution.

  17. Photochemical formation of hydroxyl radical from effluent organic matter.

    PubMed

    Dong, Mei Mei; Rosario-Ortiz, Fernando L

    2012-04-03

    The photochemical formation of hydroxyl radical (HO•) from effluent organic matter (EfOM) was evaluated using three bulk wastewater samples collected at different treatment facilities under simulated sunlight. For the samples studied, the formation rates of HO•(R(HO•)) were obtained from the formation rate of phenol following the hydroxylation of benzene. The values of R(HO•) ranged from 2.3 to 3.8 × 10(-10) M s(-1) for the samples studied. The formation rate of HO• from nitrate photolysis (R(NO3)(HO•)) was determined to be 3.0 × 10(-7) M(HO)• M(NO3)(-1) s(-1). The HO• production rate from EfOM (R(EfOM)(HO•)) ranged from 0.76 to 1.3 × 10(-10) M s(-1). For the wastewater samples studied, R(EfOM)(HO•) varied from 1.5 to 2.4 × 10(-7) M(HO)• M(C)(-1) (s-1) on molarcarbon basis, which was close to HO• production from nitrate photolysis. The apparent quantum yield for the formation of HO• from nitrate (Φ(NO3-HO•)(a)) was determined as 0.010 ± 0.001 for the wavelength range 290-400 nm in ultrapure water. The apparent quantum yield for HO• formation in EfOM (Φ(EfOM-HO•)(a)) ranged from 6.1 to 9.8 × 10(-5), compared to 2.99 to 4.56 × 10(-5) for organic matter (OM) isolates. The results indicate that wastewater effluents could produce significant concentrations of HO•, as shown by potential higher nitrate levels and relatively higher quantum yields of HO• formation from EfOM.

  18. Hyperglycemia induces apoptosis in rat liver through the increase of hydroxyl radical: new insights into the insulin effect.

    PubMed

    Francés, Daniel E; Ronco, María T; Monti, Juan A; Ingaramo, Paola I; Pisani, Gerardo B; Parody, Juan P; Pellegrino, José M; Sanz, Paloma Martín; Carrillo, María C; Carnovale, Cristina E

    2010-05-01

    In this study, we analyzed the contribution of hydroxyl radical in the liver apoptosis mediated by hyperglycemia through the Bax-caspase pathway and the effects of insulin protection against the apoptosis induced by hyperglycemia. Male adult Wistar rats were randomized in three groups: control (C) (sodium citrate buffer, i.p.), streptozotocin (STZ)-induced diabetic (SID) (STZ 60 mg/kg body weight, i.p.), and insulin-treated SID (SID+I; 15 days post STZ injection, SID received insulin s.c., twice a day, 15 days). Rats were autopsied on day 30. In liver tissue, diabetes promoted a significant increase in hydroxyl radical production which correlated with lipid peroxidation (LPO) levels. Besides, hyperglycemia significantly increased mitochondrial BAX protein expression, cytosolic cytochrome c levels, and caspase-3 activity leading to an increase in apoptotic index. Interestingly, the treatment of diabetic rats with desferoxamine or tempol (antioxidants/hydroxyl radical scavengers) significantly attenuated the increase in both hydroxyl radical production and in LPO produced by hyperglycemia, preventing apoptosis by reduction of mitochondrial BAX and cytosolic cytochrome c levels. Insulin treatment showed similar results. The finding that co-administration of antioxidants/hydroxyl radical scavengers together with insulin did not provide any additional benefit compared with those obtained using either inhibitors or insulin alone shows that it is likely that insulin prevents oxidative stress by reducing the effects of hydroxyl radicals. Importantly, insulin significantly increased apoptosis inhibitor protein expression by induction of its mRNA. Taken together, our studies support that, at least in part, the hydroxyl radical acts as a reactive intermediate, which leads to liver apoptosis in a model of STZ-mediated hyperglycemia. A new anti-apoptosis signal for insulin is shown, given by an increase of apoptosis inhibitor protein.

  19. Measurements of snow grain hydroxyl radical at Summit, Greenland

    NASA Astrophysics Data System (ADS)

    Anastasio, C.; Galbavy, E.; Hutterli, M.; Friel, D.; Bales, R.

    2004-12-01

    Sunlit snowpacks release a number of volatile organic compounds (VOCs) such as formaldehyde and other carbonyls, carboxylic acids, alkenes, and alkyl halides. It has been hypothesized that this flux of VOCs to the overlying atmosphere is in part due to reactions of hydroxyl radical (OH) with snowgrain organic matter. Recent laboratory measurements by Grannas et al. support this idea by showing that the photolysis of polar snow releases formaldehyde, and that this release is enhanced by the addition of nitrate, a photochemical source of OH. In addition to its effects on organic chemistry, OH is probably also important in other snowpack reactions such as the oxidation of halides to form volatile, reactive gaseous halogens. However, the possible role of OH in these reactions has not been quantified. To begin to address the importance of OH in snowpack chemistry, we have measured the photochemical formation of hydroxyl radicals on snow grains at Summit, Greenland during the spring and summer. Measurements were made using a chemical probe technique where benzoate is added to the snow sample in order to scavenge OH and convert it into p-hydroxybenzoate, which is measured by HPLC. We found that OH is formed on snow grains during both seasons and that the rate of formation in the summer was more than an order of magnitude greater than the typical springtime value. Expressed on a bulk (melted) snow volume basis, the average summer value was approximately 200 nM/hr. Assuming that this reactivity occurs within a snowgrain "quasi-liquid layer" (QLL) that represents approximately 0.001% of the bulk liquid volume, rates of OH photoformation in the QLL are on the order of 10 mM/hr. The possible implications of this enormous rate of OH formation for snowpack chemistry (e.g., for VOC release) will be discussed. We have also examined the relative importance of nitrate and hydrogen peroxide as sources of photoformed OH on snow grains at Summit. Based on quantum yields determined in

  20. The reaction of methyl peroxy and hydroxyl radicals as a major source of atmospheric methanol

    NASA Astrophysics Data System (ADS)

    Müller, Jean-François; Liu, Zhen; Nguyen, Vinh Son; Stavrakou, Trissevgeni; Harvey, Jeremy N.; Peeters, Jozef

    2016-10-01

    Methyl peroxy, a key radical in tropospheric chemistry, was recently shown to react with the hydroxyl radical at an unexpectedly high rate. Here, the molecular reaction mechanisms are elucidated using high-level quantum chemical methodologies and statistical rate theory. Formation of activated methylhydrotrioxide, followed by dissociation into methoxy and hydroperoxy radicals, is found to be the main reaction pathway, whereas methylhydrotrioxide stabilization and methanol formation (from activated and stabilized methylhydrotrioxide) are viable minor channels. Criegee intermediate formation is found to be negligible. Given the theoretical uncertainties, useful constraints on the yields are provided by atmospheric methanol measurements. Using a global chemistry-transport model, we show that the only explanation for the high observed methanol abundances over remote oceans is the title reaction with an overall methanol yield of ~30%, consistent with the theoretical estimates given their uncertainties. This makes the title reaction a major methanol source (115 Tg per year), comparable to global terrestrial emissions.

  1. The reaction of methyl peroxy and hydroxyl radicals as a major source of atmospheric methanol.

    PubMed

    Müller, Jean-François; Liu, Zhen; Nguyen, Vinh Son; Stavrakou, Trissevgeni; Harvey, Jeremy N; Peeters, Jozef

    2016-10-17

    Methyl peroxy, a key radical in tropospheric chemistry, was recently shown to react with the hydroxyl radical at an unexpectedly high rate. Here, the molecular reaction mechanisms are elucidated using high-level quantum chemical methodologies and statistical rate theory. Formation of activated methylhydrotrioxide, followed by dissociation into methoxy and hydroperoxy radicals, is found to be the main reaction pathway, whereas methylhydrotrioxide stabilization and methanol formation (from activated and stabilized methylhydrotrioxide) are viable minor channels. Criegee intermediate formation is found to be negligible. Given the theoretical uncertainties, useful constraints on the yields are provided by atmospheric methanol measurements. Using a global chemistry-transport model, we show that the only explanation for the high observed methanol abundances over remote oceans is the title reaction with an overall methanol yield of ∼30%, consistent with the theoretical estimates given their uncertainties. This makes the title reaction a major methanol source (115 Tg per year), comparable to global terrestrial emissions.

  2. The reaction of methyl peroxy and hydroxyl radicals as a major source of atmospheric methanol

    PubMed Central

    Müller, Jean-François; Liu, Zhen; Nguyen, Vinh Son; Stavrakou, Trissevgeni; Harvey, Jeremy N.; Peeters, Jozef

    2016-01-01

    Methyl peroxy, a key radical in tropospheric chemistry, was recently shown to react with the hydroxyl radical at an unexpectedly high rate. Here, the molecular reaction mechanisms are elucidated using high-level quantum chemical methodologies and statistical rate theory. Formation of activated methylhydrotrioxide, followed by dissociation into methoxy and hydroperoxy radicals, is found to be the main reaction pathway, whereas methylhydrotrioxide stabilization and methanol formation (from activated and stabilized methylhydrotrioxide) are viable minor channels. Criegee intermediate formation is found to be negligible. Given the theoretical uncertainties, useful constraints on the yields are provided by atmospheric methanol measurements. Using a global chemistry-transport model, we show that the only explanation for the high observed methanol abundances over remote oceans is the title reaction with an overall methanol yield of ∼30%, consistent with the theoretical estimates given their uncertainties. This makes the title reaction a major methanol source (115 Tg per year), comparable to global terrestrial emissions. PMID:27748363

  3. Coumestan inhibits radical-induced oxidation of DNA: is hydroxyl a necessary functional group?

    PubMed

    Xi, Gao-Lei; Liu, Zai-Qun

    2014-06-18

    Coumestan is a natural tetracycle with a C═C bond shared by a coumarin moiety and a benzofuran moiety. In addition to the function of the hydroxyl group on the antioxidant activity of coumestan, it is worth exploring the influence of the oxygen-abundant scaffold on the antioxidant activity as well. In this work, seven coumestans containing electron-withdrawing and electron-donating groups were synthesized to evaluate the abilities to trap 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS(•+)), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH), and galvinoxyl radical, respectively, and to inhibit the oxidations of DNA mediated by (•)OH, Cu(2+)/glutathione (GSH), and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH), respectively. It was found that all of the coumestans used herein can quench the aforementioned radicals and can inhibit (•)OH-, Cu(2+)/GSH-, and AAPH-induced oxidations of DNA. In particular, substituent-free coumestan exhibits higher ability to quench DPPH and to inhibit AAPH-induced oxidation of DNA than Trolox. In addition, nonsubstituted coumestan shows a similar ability to inhibit (•)OH- and Cu(2+)/GSH-induced oxidations of DNA relative to that of Trolox. The antioxidant effectiveness of the coumestan can be attributed to the lactone in the coumarin moiety and, therefore, a hydroxyl group may not be a necessary functional group for coumestan to be an antioxidant.

  4. ESR ST study of hydroxyl radical generation in wet peroxide system catalyzed by heterogeneous ruthenium.

    PubMed

    Rokhina, Ekaterina V; Golovina, Elena A; As, Henk van; Virkutyte, Jurate

    2009-09-01

    Ru-based catalysts gained popularity because of their applicability for a variety of processes, including carbon monoxide oxidation, wet air catalytic oxidation and wastewater treatment. The focus of a current study was generation of hydroxyl radicals in the wet peroxide system catalyzed by heterogeneous ruthenium, spin-trapped by DEPMPO and DIPPMPO by means of electron spin resonance spin-trapping technique (ESR ST). The mechanism of free radicals formation was proposed via direct cleavage of hydrogen peroxide over ruthenium active sites. The chemical reactions occurring in the system were introduced according to the experimental results. Also, radical production rate was assessed based on concentration changes of species involved in the bulk liquid phase oxidation.

  5. Hydroxyl radical oxidation of cylindrospermopsin (cyanobacterial toxin) and its role in the photochemical transformation.

    PubMed

    Song, Weihua; Yan, Shuwen; Cooper, William J; Dionysiou, Dionysios D; O'Shea, Kevin E

    2012-11-20

    Cylindrospermopsin (CYN), an alkaloid guanidinium sulfated toxin, is produced by a number of cyanobacteria regularly found in lakes, rivers, and reservoirs. Steady-state and time-resolved radiolysis methods were used to determine reaction pathways and kinetic parameters for the reactions of hydroxyl radical with CYN. The absolute bimolecular reaction rate constant for the reaction of hydroxyl radical with CYN is (5.08 ± 0.16) × 10(9) M(-1) s(-1). Comparison of the overall reaction rate of CYN with hydroxyl radical with the individual reaction rate for addition to the uracil ring in CYN indicate the majority of the hydroxyl radicals (84%) react at the uracil functionality of CYN. Product analyses using liquid chromatography-mass spectrometry indicate the major products from the reaction of hydroxyl radical with CYN involve attack of hydroxyl radical at the uracil ring and hydrogen abstraction from the hydroxy-methine bridge linking the uracil ring to the tricyclic guanidine functionality. The role of hydroxyl radical initiated pathways in the natural organic matter (NOM) photosensitized transformation of CYN were evaluated. Scavenger and trapping experiments indicate that hydroxyl radical mediated transformations account for approximately ~70% of CYN destruction in surface waters under solar irradiation in the presence of NOM. The absence of solvent isotope effect indicates singlet oxygen does not play a significant role in the NOM sensitized transformation of CYN. The primary degradation pathways for HO• mediated and NOM photosensitized destruction of CYN involve destruction of the uracil ring. The fundamental kinetic parameters determined from these studies are critical for the accurate evaluation of hydroxyl-radical based technologies for the remediation of this problematic cyanotoxin in drinking water and important in the assessment of the environmental oxidative transformation of uracil based compounds.

  6. A QSAR for the hydroxyl radical reaction rate constant: validation, domain of application, and prediction

    NASA Astrophysics Data System (ADS)

    Öberg, Tomas

    A large number of anthropogenic organic chemicals are emitted into the troposphere. Reactions with the hydroxyl radical are a dominant removal pathway for most organic compounds, but experimentally determined gas-phase reaction rate constants are only available for about 750 compounds. The lack of experimental data increases the importance of applying quantitative structure-activity relationships (QSAR) to evaluate and predict reactivities. It is generally acknowledged that these empirical relationships are valid only within the same domain for which they were developed. However, model validation is sometimes neglected and the application domain is not always well defined. The purpose of this paper is to outline how validation and domain definition can facilitate the modeling and prediction of the hydroxyl radical reaction rates for a large database. A substantial number of theoretical descriptors (867) were generated from 2D molecular structures for compounds present in the Syracuse Research Corporation's PhysProp Database. A QSAR model was developed for the hydroxyl radical reaction rate constant using a projection-based regression technique, partial least squares regression (PLSR). The PLSR model was subsequently validated with an external test set. The main factors of variation could be attributed to two reaction pathways, hydrogen atom abstraction and addition to double bonds or aromatic systems. A set of 17 293 compounds, drawn from the PhysProp Database, was projected onto the PLSR model and 74% were inside the applicability domain. The predicted hydroxyl reaction rates for 25% of these compounds were slow or negligible, with atmospheric half-lives in the range from days to years. Finally, the list of persistent organic compounds was matched against the OECD list of high production volume chemicals (HPVC). Together with the experimental data, nearly three hundred compounds were identified as both persistent and in high volume production.

  7. Interactive enhancements of ascorbic acid and iron in hydroxyl radical generation in quinone redox cycling.

    PubMed

    Li, Yi; Zhu, Tong; Zhao, Jincai; Xu, Bingye

    2012-09-18

    Quinones are toxicological substances in inhalable particulate matter (PM). The mechanisms by which quinones cause hazardous effects can be complex. Quinones are highly active redox molecules that can go through a redox cycle with their semiquinone radicals, leading to formation of reactive oxygen species. Electron spin resonance spectra have been reported for semiquinone radicals in PM, indicating the importance of ascorbic acid and iron in quinone redox cycling. However, these findings are insufficient for understanding the toxicity associated with quinone exposure. Herein, we investigated the interactions among anthraquinone (AQ), ascorbic acid, and iron in hydroxyl radical (·OH) generation through the AQ redox cycling process in a physiological buffer. We measured ·OH concentration and analyzed the free radical process. Our results showed that AQ, ascorbic acid, and iron have synergistic effects on ·OH generation in quinone redox cycling; i.e., ascorbyl radical oxidized AQ to semiquinone radical and started the redox cycling, iron accelerated this oxidation and enhanced ·OH generation through Fenton reactions, while ascorbic acid and AQ could help iron to release from quartz surface and enhance its bioavailability. Our findings provide direct evidence for the redox cycling hypothesis about airborne particle surface quinone in lung fluid.

  8. Photoformation of hydroxyl radical on snow grains at Summit, Greenland

    NASA Astrophysics Data System (ADS)

    Anastasio, Cort; Galbavy, Edward S.; Hutterli, Manuel A.; Burkhart, John F.; Friel, Donna K.

    We measured the photoformation of hydroxyl radical ( ṡOH) on snow grains at Summit, Greenland during the spring and summer. Midday rates of ṡOH formation in the snow phase in the summer range from 130 to 610nmolL-1h-1, expressed relative to the liquid equivalent volume of snow. Calculated formation rates of snow-grain ṡOH based on the photolysis of hydrogen peroxide and nitrate agree well with our measured rates during summer, indicating that there are probably not other major sources of ṡOH under these conditions. Throughout both the spring and summer, HOOH is by far the dominant source of snow-grain ṡOH; on average, HOOH produces approximately 100 times more ṡOH than does NO3-. Rates of ṡOH photoformation have a strong seasonal dependence and increase by approximately a factor of 10 between early spring and summer at midday. The rate of ṡOH photoformation on snow grains decreases rapidly with depth in the snowpack, with approximately 90% of photoformation occurring within the top 10 cm, although ṡOH formation occurs to depths below 20 cm. The formation of ṡOH on snow grains likely initiates a suite of reactions in the snowpack, including the transformation of organic carbon (OC) and oxidation of halides. The reaction of ṡOH with OC probably forms a number of volatile organic compounds (VOCs) that are potentially emitted into the atmospheric boundary layer. Indeed, our measured rates of ṡOH photoformation on snow grains are large enough that they could account for previously reported fluxes of VOCs from the snowpack at Summit, although the relative importance of thermal desorption and photochemical production for most of these VOCs still needs to be determined.

  9. Relevance of the capacity of phosphorylated fructose to scavenge the hydroxyl radical.

    PubMed

    Spasojević, Ivan; Mojović, Milos; Blagojević, Dusko; Spasić, Snezana D; Jones, David R; Nikolić-Kokić, Aleksandra; Spasić, Mihajlo B

    2009-01-05

    The hydroxyl radical (*OH) has detrimental biological activity due to its very high reactivity. Our experiments were designed to determine the effects of equimolar concentrations of glucose, fructose and mannitol and three phosphorylated forms of fructose (fructose-1-phosphate (F1P); fructose-6-phosphate (F6P); and fructose-1,6-bis(phosphate) (F16BP)) on *OH radical production via the Fenton reaction. EPR spectroscopy using spin-trap DEPMPO was applied to detect radical production. We found that the percentage inhibition of *OH radical formation decreased in the order F16BP>F1P>F6P>fructose>mannitol=glucose. As ketoses can sequester redox-active iron thus preventing the Fenton reaction, the Haber-Weiss-like system was also employed to generate *OH, so that the effect of iron sequestration could be distinguished from direct *OH radical scavenging. In the latter system, the rank order of *OH scavenging activity was F16BP>F1P>F6P>fructose=mannitol=glucose. Our results clearly demonstrate that intracellular phosphorylated forms of fructose have more scavenging properties than fructose or glucose, leading us to conclude that the acute administration of fructose could overcome the body's reaction to exogenous antioxidants during appropriate therapy in certain pathophysiological conditions related to oxidative stress, such as sepsis, neurodegenerative diseases, atherosclerosis, malignancy, and some complications of pregnancy.

  10. Ratiometric coumarin-neutral red (CONER) nanoprobe for detection of hydroxyl radicals.

    PubMed

    Ganea, Gabriela M; Kolic, Paulina E; El-Zahab, Bilal; Warner, Isiah M

    2011-04-01

    Excessive production of reactive oxygen species can lead to alteration of cellular functions responsible for many diseases including cardiovascular diseases, neurodegenerative diseases, cancer, and aging. Hydroxyl radical is a short-lived radical which is considered very aggressive due to its high reactivity toward biological molecules. In this study, a COumarin-NEutral Red (CONER) nanoprobe was developed for detection of hydroxyl radical based on the ratiometric fluorescence signal between 7-hydroxy coumarin 3-carboxylic acid and neutral red dyes. Biocompatible poly lactide-co-glycolide (PLGA) nanoparticles containing encapsulated neutral red were produced using a coumarin 3-carboxylic acid conjugated poly(sodium N-undecylenyl-Nε-lysinate) (C3C-poly-Nε-SUK) as moiety reactive to hydroxyl radicals. The response of the CONER nanoprobe was dependent on various parameters such as reaction time and nanoparticle concentration. The probe was selective for hydroxyl radicals as compared with other reactive oxygen species including O(2)(•-), H(2)O(2), (1)O(2), and OCl(-). Furthermore, the CONER nanoprobe was used to detect hydroxyl radicals in vitro using viable breast cancer cells exposed to oxidative stress. The results suggest that this nanoprobe represents a promising approach for detection of hydroxyl radicals in biological systems.

  11. Involvement of inducible nitric oxide synthase in hydroxyl radical-mediated lipid peroxidation in streptozotocin-induced diabetes

    PubMed Central

    Stadler, Krisztian; Bonini, Marcelo G.; Dallas, Shannon; Jiang, JinJie; Radi, Rafael; Mason, Ronald P.; Kadiiska, Maria B.

    2008-01-01

    Free radical production is implicated in the pathogenesis of diabetes mellitus, where several pathways and different mechanisms were suggested in the pathophysiology of the complications. In this study, we used electron paramagnetic resonance (EPR) spectroscopy combined with in vivo spin-trapping techniques to investigate the sources and mechanisms of free radical formation in streptozotocin-induced diabetic rats. Free radical production was directly detected in the diabetic bile, which correlated with lipid peroxidation in the liver and kidney. EPR spectra showed the trapping of a lipid-derived radical. Such radicals were demonstrated to be induced by hydroxyl radical through isotope labeling experiments. Multiple enzymes and metabolic pathways were examined as the potential source of the hydroxyl radicals using specific inhibitors. Neither xanthine oxidase, cytochrome P450s, the Fenton reaction, nor macrophage activation were required for the production of radical adducts. Interestingly, inducible nitric oxide synthase (apparently uncoupled) was identified as the major source of radical generation. The specific iNOS inhibitor 1400W as well as l-arginine pretreatment reduced the EPR signals to baseline levels, implicating peroxynitrite as the source of hydroxyl radical production. Applying immunological techniques, we localized iNOS overexpression in the liver and kidney of diabetic animals, which was closely correlated with the lipid radical generation and 4-hydroxynonenal-adducted protein formation, indicating lipid peroxidation. In addition, protein oxidation to protein free radicals occurred in the diabetic target organs. Taken together, our studies support inducible nitric oxide synthase as a significant source of EPR-detectable reactive intermediates, which leads to lipid peroxidation and may contribute to disease progression as well. PMID:18620046

  12. Fast repair of thymine-hydroxyl radical adduct by phenylpropanoid glycosides

    NASA Astrophysics Data System (ADS)

    Wenyan, Li; Zhihua, Zou; Rongliang, Zheng; Changzeng, Wang; Zhongjian, Jia; Side, Yao; Nianyun, Lin

    1997-04-01

    The repair effect on thymine-hydroxyl adduct by phenylpropanoid glycosides (PPG): verbascoside, and pedicularioside A, isolated from Pedicularis, were studied using pulse radiolysis technique. From the analysis of transient absorption spectra, the rapid electron transfer from PPG to T-OH - was observed. Phenoxyl radical of PPG were generated via one-electron-transfer reaction. This result showed that two PPG exhibited repair activities on oxidizing T-OH -. The reaction rate constants of electron transfer from PPGs were 1.27 × 10 9 and 1.29 × 10 9 dm 3·mol -1s -1 respectively.

  13. Use of high-performance liquid chromatography to detect hydroxyl and superoxide radicals generated from mitomycin C.

    PubMed

    Pritsos, C A; Constantinides, P P; Tritton, T R; Heimbrook, D C; Sartorelli, A C

    1985-11-01

    Distinguishing between short-lived reactive oxygen species like hydroxyl and superoxide radicals is difficult; the most successful approaches employ electron spin resonance (ESR) spin-trapping techniques. Using the spin trap 5,5-dimethyl-l-pyrroline N-oxide (DMPO) to selectively trap various radicals in the presence and absence of ethanol, an HPLC system which is capable of separating the hydroxyl- and superoxide-generated DMPO adduct species has been developed. The radical-generated DMPO adducts were measured with an electrochemical detector attached to the HPLC system and confirmed by spin-trapping techniques. The HPLC separation was carried out on an ODS reverse-phase column with a pH 5.1 buffered 8.5% acetonitrile mobile phase. The advantage of the HPLC system described is that it permits the separation and detection of hydroxyl and superoxide radicals without requiring ESR instrumentation. The antineoplastic bioreductive alkylating agent mitomycin C, when activated by NADPH-cytochrome c reductase, was shown to generate both hydroxyl and superoxide radicals.

  14. Hydroxyl-radical-dependent DNA damage by ambient particulate matter from contrasting sampling locations

    SciTech Connect

    Shi Tingming; Duffin, Rodger; Borm, Paul J.A.; Li Hui; Weishaupt, Christel; Schins, Roel P.F. . E-mail: roel.schins@uni-duesseldorf.de

    2006-05-15

    Exposure to ambient particulate matter (PM) has been reported to be associated with increased respiratory, cardiovascular, and malignant lung disease. Previously we have shown that PM can induce oxidative DNA damage in A549 human lung epithelial cells. The aims of the present study were to investigate the variability of the DNA-damaging properties of PM sampled at different locations and times and to relate the observed effects to the hydroxyl-radical ({center_dot}OH)-generating activities of these samples. Weekly samples of coarse (10-2.5 {mu}m) and fine (<2.5 {mu}m) PM from four sites (Nordrheim Westfalen, Germany) were analyzed for hydrogen-peroxide-dependent {center_dot}OH formation using electron paramagnetic resonance and formation of 8-hydroxydeoxyguanosine (8-OHdG) in calf thymus DNA using an immuno-dot-blot assay. DNA strand breakage by fine PM in A549 human lung epithelial cells was quantified using the alkaline comet assay. Both PM size distribution fractions elicited {center_dot}OH generation and 8-OHdG formations in calf thymus DNA. Significantly higher {center_dot}OH generation was observed for PM sampled at urban/industrial locations and for coarse PM. Samples of fine PM also caused DNA strand breakage in A549 cells and this damage could be prevented using the hydroxyl-radical scavengers 5,5-dimethyl-1-pyrroline-N-oxide and dimethyl sulfoxide. The observed DNA strand breakage appeared to correlate with the hydroxyl-radical-generating capacities of the PM samples but with different profiles for rural versus urban/industrial samples. In conclusion, when considered at equal mass, {center_dot}OH formation of PM shows considerable variability with regard to the sampling location and time and is correlated with its ability to cause DNA damage.

  15. Rapid screening, separation, and detection of hydroxyl radical scavengers from total flavonoids of Ginkgo biloba leaves by chromatography combined with molecular devices.

    PubMed

    Wang, Jing; Zheng, Meizhu; Chen, Lina; Liu, Zhiqiang; Zhang, Yuchi; Liu, Chun-Ming; Liu, Shu

    2016-11-01

    Hydroxyl radicals are the most reactive free radical of human body, a strong contributor to tissue damage. In this study, liquid chromatography coupled to electrospray ionization mass spectrometry was applied to screen and identify hydroxyl radical scavengers from the total flavonoids of Ginkgo biloba leaves, and high-performance counter current chromatography was used to separate and isolate the active compounds. Furthermore, molecular devices were used to determine hydroxyl radical scavenging activities of the obtained hydroxyl radical scavengers and other flavonoids from G. biloba leaves. As a result, six compounds were screened as hydroxyl radical scavengers, but only three flavonoids, namely, rutin, cosmos glycosides and apigenin-7-O-Glu-4'-O-Rha, were isolated successfully from total flavonoids by high-performance counter current chromatography. The purities of the three obtained compounds were over 90%, respectively, as determined by liquid chromatography. Molecular devices with 96-well microplates evaluation indicated that the 50% scavenging concentration values of screened compounds were lower than that of other flavonoids, they performed greater hydroxyl radical scavenging activity, and the evaluation effects were consistent with the liquid chromatography with mass spectrometry screening results. Therefore, chromatography combined with molecular devices is a feasible and an efficient method for systematic screening, identification, isolation, and evaluation of bioactive components in mixture of botanical medicines.

  16. Inhibition of hydroxyl radical reaction with aromatics by dissolved natural organic matter

    USGS Publications Warehouse

    Lindsey, M.E.; Tarr, M.A.

    2000-01-01

    Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compound molecules bound to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H2O2 + Fe2+ ??? Fe3+ + HO- + HO??). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanism for the observed inhibition is that hydroxyl radical formation occurs in microenvironmental sites remote from the aromatic compounds. In addition to changes in kinetics, pyrene hydroxyl radical reaction also exhibited a mechanistic change in the presence of fulvic acid. The mechanism changed from a reaction that was apparently firstorder in pyrene to one that was apparently secondorder in pyrene, indicating that pyrene self-reaction may have become the dominant mechanism in the presence of fulvic acid. Dissolved NOM causes significant changes in the rate and mechanism of hydroxyl radical degradation of aromatic compounds. Consequently, literature rate constants measured in pure water will not be useful for predicting the degradation of pollutants in environmental systems. The kinetic and mechanistic information in this study will be useful for developing improved degradation methods involving Fenton chemistry.Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compounds molecules bounds to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H2O2 + Fe2+ ??? Fe3+ + HO- + HO??). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanisms for the observed inhibition is that hydroxyl radical

  17. Atmospheric hydroxyl radical production from electronically excited NO2 and H2O.

    PubMed

    Li, Shuping; Matthews, Jamie; Sinha, Amitabha

    2008-03-21

    Hydroxyl radicals are often called the "detergent" of the atmosphere because they control the atmosphere's capacity to cleanse itself of pollutants. Here, we show that the reaction of electronically excited nitrogen dioxide with water can be an important source of tropospheric hydroxyl radicals. Using measured rate data, along with available solar flux and atmospheric mixing ratios, we demonstrate that the tropospheric hydroxyl contribution from this source can be a substantial fraction (50%) of that from the traditional O(1D) + H2O reaction in the boundary-layer region for high solar zenith angles. Inclusion of this chemistry is expected to affect modeling of urban air quality, where the interactions of sunlight with emitted NOx species, volatile organic compounds, and hydroxyl radicals are central in determining the rate of ozone formation.

  18. RAPID MEASUREMENT OF AQUEOUS HYDROXYL RADICAL CONCENTRATIONS IN STEADY-STATE HO· FLUX SYSTEMS

    EPA Science Inventory

    The spin-trap compound a-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone (4-POBN) is utilized for the detection and quantitation of the hydroxyl radical (HO·) in aqueous solution. Capillary electrophoresis enables rapid analysis of the probe compound. The thermally unstable HO· radical ...

  19. Effect of apotransferrin, lactoferrin and ovotransferrin on the hydroxyl radical mediated degradation of beta-glucan.

    PubMed

    Faure, Audrey M; Nyström, Laura

    2016-08-01

    Beta-glucan is a polysaccharide widely accepted and used as a functional ingredient due to its positive effects on human health. However, beta-glucan is readily degraded in aqueous systems in presence of a hydroxyl radical generating system such as ascorbic/iron(II). In the present study, we tested whether iron binding proteins; apotransferrin, lactoferrin and ovotransferrin; could prevent the hydroxyl radical mediated degradation of beta-glucan. The radical formation was investigated by ESR spectroscopy and the polysaccharide degradation was monitored by the viscosity loss of the solutions. Apo-transferrin increased the formation of hydroxyl radicals and this related with a faster degradation of beta-glucan. Lactoferrin did not have any effect on the ascorbate induced degradation of beta-glucan, whereas ovotransferrin completely inhibited the hydroxyl radical generation by a system containing ascorbic acid and iron(II). However, the presence of ovotransferrin in beta-glucan decreased the viscosity of the solution, which was accompanied by the apparition of a precipitate, indicating a potential interaction between the protein and beta-glucan. FT-IR analyses indicate the presence of beta-glucan and ovotransferrin in both precipitate and supernatant, as well as the occurrence of interactions between the two compounds. This study reveals that ovotransferrin is a promising candidate for inhibiting the formation of ascorbate/iron(II) induced hydroxyl radicals in beta-glucan solutions.

  20. Hydroxyl radical regeneration in isoprene oxidation: upgraded mechanism LIM1

    NASA Astrophysics Data System (ADS)

    Peeters, Jozef; Son Nguyen, Vinh; Nguyen, Thanh Lam; Stravrakou, Trissevgeni; Muller, Jean-Francois

    2013-04-01

    The OH regeneration known to occur in isoprene oxidation at low/moderate NO is attributed in the Leuven Isoprene Mechanism to novel, theoretically characterized chemical pathways (LIM0: Peeters et al. 2009; Peeters and Muller 2010). Its key new features are (i) quasi-equilibration of the thermally labile beta-OH- and delta-OH-isoprenylperoxy isomers; (ii) 1,6-H shift isomerisation of the Z-delta-OH-peroxy isomers to yield hydroperoxy-methyl-butenals (HPALDs); (iii) fast photolysis of the HPALDs resulting overall in several OH radicals per HPALD. The OH-regeneration through photolabile HPALDs has recently found experimental support, but the peroxy isomerisation rate, HPALD yield and extent of OH recycling are still uncertain (Crounse et al. 2011; Wolfe et al. 2012). In this work, the upgraded LIM1 mechanism is presented. Based on much higher levels of theory that fully account for dispersion effects, the crucial equilibrium ratio of the isomerising Z-delta-OH-peroxys over the majority beta-OH-isoprenylperoxys is reduced by a factor ≈5 and the isomerisation rate of the Z-delta-OH-peroxys by a factor ≈1.5 compared to LIM0. The chemistry following the 1,6-H shift of the Z-delta-OH-peroxys is also much expanded and extended. Firstly, LIM1 introduces other pathways beside HPALD formation following the Z-delta-OH-peroxy isomerisation, but resulting likewise in OH recycling. This, together with the revised Z-delta-OH- equilibrium and isomerisation data above, affords a fair model-reproduction of the HPALD and other product yields observed by Crounse et al. (2011). Secondly, LIM1 proposes new fast reactions of HO2 with the alpha-oxoketene products from the peroxy isomerisation routes; these reactions are shown to efficiently convert HO2 into OH and are prime candidates for the unknown X + HO2 → OH + ... hydroxyl-recycling routes invoked in recent studies (Hofzumahaus et al.2009; Whalley et al. 2011). Modeling results using the IMAGES global CTM will be presented on

  1. Differential roles of hydrogen peroxide and hydroxyl radical in cisplatin-induced cell death in renal proximal tubular epithelial cells.

    PubMed

    Baek, Su Mi; Kwon, Chae Hwa; Kim, Jae Ho; Woo, Jae Suk; Jung, Jin Sup; Kim, Yong Keun

    2003-09-01

    Reactive oxygen species (ROS) have been suggested as important mediators of cisplatin-induced acute renal failure in vivo. However, our previous studies have shown that cisplatin-induced cell death in vitro could not be prevented by scavengers of hydrogen peroxide and hydroxyl radical in rabbit renal cortical slices. This discrepancy may be attributed to differential roles of ROS in necrotic and apoptotic cell death. We therefore examined, in this study, the roles of ROS in necrosis and apoptosis induced by cisplatin in primary cultured rabbit proximal tubule. Cisplatin induced necrosis at high concentrations over a few hours and apoptosis at much lower concentrations over longer periods. Necrosis induced by high concentration of cisplatin was prevented by a cell-permeable superoxide scavenger (tiron), hydrogen peroxide scavengers (catalase and pyruvate), and antioxidants (Trolox and deferoxamine), whereas hydroxyl radical scavengers (dimethythiourea and thiourea) did not affect the cisplatin-induced necrosis. However, apoptosis induced by lower concentration of cisplatin was partially prevented by tiron and hydroxyl radical scavengers but not by hydrogen peroxide scavengers and antioxidants. Cisplatin-induced apoptosis was mediated by the signaling pathway that is associated with cytochrome c release from mitochondria and caspase-3 activation. These effects were prevented by tiron and dimethylthiourea but not by catalase. Dimethylthiourea produced a significant protection against cisplatin-induced acute renal failure, and the effect was associated with an inhibition of apoptosis. These results suggest that hydrogen peroxide is involved in the cisplatin-induced necrosis, whereas hydroxyl radical is responsible for the cisplatin-induced apoptosis. The protective effects of hydroxyl radical scavengers are associated with an inhibition of cytochrome c release and caspase activation.

  2. Efficacy of puffer fish (Takifugu rubripes) sauce in reducing hydroxyl radical damage to DNA assessed using the apurinic/apyrimidinic site method.

    PubMed

    Harada, Kazuki; Makino, Yoshio; Yamauchi, Tomio; Fukuda, Nami; Tamaru, Miki; Okubo, Yasue; Maeda, Toshimichi; Fukuda, Yutaka; Shiba, Tsuneo

    2007-09-01

    Apurinic/apyrimidinic (AP) sites are frequently observed DNA lesions when cells are exposed to hydroxyl radicals. We developed a new method for measurement of the antioxidative activity of foods using the occurrence frequency of AP sites on DNA. Combined with the electron spin resonance (ESR) method as a standard method, we examined whether fish and soy sauces including puffer fish [Takifugu rubripes (Temminck et Schlegel)] sauce could protect DNA from damage caused by hydroxyl radicals. The results showed that the ratios of DNA protection by puffer fish sauce, salmon fish sauce, sandfish fish sauce (Shottsuru), colorless soy sauce, squid fish sauce (Ishiru), dark color soy sauce and light color soy sauce were 68.9, 67.0, 60.1, 49.7, 34.1, 28.2 and -4.4%, respectively. Puffer, salmon, and sandfish fish sauces showed high ratios of DNA protection against hydroxyl radicals. On the other hand, IC(50) values of hydroxyl radical scavenging of the puffer, salmon, sandfish, squid fish sauces and colorless, dark and light color soy sauces were 0.20, 0.09, 4.16, 0.26% and 0.28, 0.14 and 0.18%, respectively. Though the puffer fish sauce exhibited the highest level of DNA protection among the examined samples and a high hydroxyl radical scavenging capability, a correlation between the radical scavenging capability and DNA protection against hydroxyl radicals among the examined fish and soy sauces was not found.

  3. Hydroxyl radical concentration profile in photo-Fenton oxidation process: generation and consumption of hydroxyl radicals during the discoloration of azo-dye Orange II.

    PubMed

    Maezono, Takuya; Tokumura, Masahiro; Sekine, Makoto; Kawase, Yoshinori

    2011-03-01

    Dynamic behaviors of hydroxyl (OH) radical generation and consumption in photo-Fenton oxidation process were investigated by measuring OH radical concentration during the discoloration of azo-dye Orange II. The effects of operating parameters for photo-Fenton discoloration, i.e. dosages of H(2)O(2) and Fe, initial dye concentration, solution pH and UV irradiation, on the generation and consumption of OH radicals playing the main role in advanced oxidation processes were extensively studied. The scavenger probe or trapping technique in which coumarin is scavenger of OH radical was applied to estimate OH radical concentration in the photoreactor during the photo-Fenton discoloration process. The OH radical generation was enhanced with increasing the dosages of Fenton regents, H(2)O(2) and Fe. At the initial stage of photo-Fenton discoloration of Orange II, the OH radical concentration rapidly increased (Phase-I) and the OH radical concentration decreased after reaching of OH radical concentration at maximum value (Phase-II). The decrease in OH radical concentration started when the complete discoloration of Orange II was nearly achieved and the H(2)O(2) concentration became rather low. The dynamic behavior of OH radical concentration during the discoloration of Orange II was found to be strongly linked with the change in H(2)O(2) concentration. The generation of OH radical was maximum at solution pH of 3.0 and decreased with an increase of solution pH. The OH radical generation rate in the Fenton Process was rather slower than that in the photo-Fenton process.

  4. Aliphatic peptidyl hydroperoxides as a source of secondary oxidation in hydroxyl radical protein footprinting.

    PubMed

    Saladino, Jessica; Liu, Mian; Live, David; Sharp, Joshua S

    2009-06-01

    Hydroxyl radical footprinting is a technique for studying protein structure and binding that entails oxidizing a protein system of interest with diffusing hydroxyl radicals, and then measuring the amount of oxidation of each amino acid. One important issue in hydroxyl radical footprinting is limiting amino acid oxidation by secondary oxidants to prevent uncontrolled oxidation, which can cause amino acids to appear more solvent accessible than they really are. Previous work suggested that hydrogen peroxide was the major secondary oxidant of concern in hydroxyl radical footprinting experiments; however, even after elimination of all hydrogen peroxide, some secondary oxidation was still detected. Evidence is presented for the formation of peptidyl hydroperoxides as the most abundant product upon oxidation of aliphatic amino acids. Both reverse phase liquid chromatography and catalase treatment were shown to be ineffective at eliminating peptidyl hydroperoxides. The ability of these peptidyl hydroperoxides to directly oxidize methionine is demonstrated, suggesting the value of methionine amide as an in situ protectant. Hydroxyl radical footprinting protocols require the use of an organic sulfide or similar peroxide scavenger in addition to removal of hydrogen peroxide to successfully eradicate all secondary oxidizing species and prevent uncontrolled oxidation of sulfur-containing residues.

  5. Effect of pH on Fenton process using estimation of hydroxyl radical with salicylic acid as trapping reagent.

    PubMed

    Chang, Chen-Yu; Hsieh, Yung-Hsu; Cheng, Kai-Yuan; Hsieh, Ling-Ling; Cheng, Ta-Chih; Yao, Kuo-Shan

    2008-01-01

    This study estimates the yield of hydroxyl radical using salicylic acid as the trapping reagent and investigates the relationship between hydroxyl radical and pH value. The formation and variation of hydroxyl radical under different pH values were evaluated using reaction products, 2,3-DHBA, 2,5-DHBA, and catechol. The formation rate of hydroxyl radical was dependent on the ratio of ferrous ion to hydrogen peroxide and pH values. The difference between various pH values was explored. The kinetics and mechanisms of hydroxyl radical reactions were established in the Fenton process. Experimental results showed that the best reaction conditions were 8.5 mM H(2)O(2), 1.25 mM Fe(2 + ), Fe(2 + )/H(2)O(2) = 0.147 at pH 3 and the formation rate constant of hydroxyl radical was 1.12 x 10(11) M(-1) s(-1).

  6. Anticancer system created by acrolein and hydroxyl radical generated in enzymatic oxidation of spermine and other biochemical reactions.

    PubMed

    Alarcon, R A

    2012-10-01

    A hypothesis suggesting the existence of a ubiquitous physiological anticancer system created by two highly reactive oxidative stress inducers with anticancer properties, acrolein and hydroxyl radical, is reported in this communication. Both components can originate separately or together in several biochemical interactions, among them, the enzymatic oxidation of the polyamine spermine, which appear to be their main source. The foundations of this hypothesis encompass our initial search for growth-inhibitors or anticancer compounds in biological material leading to the isolation of spermine, a polyamine that became highly cytotoxic through the generation of acrolein, when enzymatically oxidized. Findings complemented with pertinent literature data by other workers and observed anticancer activities by sources capable of producing acrolein and hydroxyl radical. This hypothesis obvious implication: spermine enzymatic oxidations or other biochemical interactions that would co-generate acrolein and hydroxyl radical, the anticancer system components, should be tried as treatments for any given cancer. The biochemical generation of acrolein observed was totally unexpected, since this aldehyde was known; as a very toxic and highly reactive xenobiotic chemical produced in the pyrolysis of fats and other organic material, found as an atmospheric pollutant, in tobacco smoke and car emissions, and mainly used as a pesticide or aquatic herbicide. Numerous studies on acrolein, considered after our work a biological product, as well, followed. In them, acrolein widespread presence, its effects on diverse cellular proteins, such as, growth factors, and its anticancer activities, were additionally reported. Regarding hydroxyl radical, the second component of the proposed anticancer system, and another cytotoxic product in normal cell metabolism, it co-generates with acrolein in several biochemical interactions, occurrences suggesting that these products might jointly fulfill some

  7. Rifampin induces hydroxyl radical formation in Mycobacterium tuberculosis.

    PubMed

    Piccaro, Giovanni; Pietraforte, Donatella; Giannoni, Federico; Mustazzolu, Alessandro; Fattorini, Lanfranco

    2014-12-01

    The antituberculosis (anti-TB) drug rifampin (RIF) binds to the beta subunit of the RNA polymerase (RpoB) of Mycobacterium tuberculosis, but the bactericidal responses triggered after target interaction are not known. To evaluate whether RIF induced an oxidative burst, lysates of RIF-treated M. tuberculosis were tested for determination of reactive oxygen species (ROS) by the electron paramagnetic resonance (EPR) technique using 1-hydroxy-3-carboxy-pyrrolidine (CPH) and 5,5-dimethyl-1-pyrrolidine-N-oxide (DMPO) as spin traps. M. tuberculosis killing by RIF stimulated an increase in the rate of formation of the CPH radical (CP·). Lysate pretreatment with the O2·(-) and ·OH scavengers superoxide dismutase (SOD) and thiourea (THIO), respectively, or with the metal chelator diethylene triamine pentaacetic acid (DTPA) inhibited CP· formation, arguing in favor of a metal-catalyzed ROS response. Formation of CP· did not increase following treatment of RIF-resistant strains with RIF, indicating that the ROS were induced after RpoB binding. To identify the ROS formed, lysates of RIF-treated bacilli were incubated with DMPO, a spin trap specific for ·OH and O2·(-), with or without pretreatment with SOD, catalase, THIO, or DTPA. Superoxide dismutase, catalase, and THIO decreased formation of the DMPO-OH adduct, and SOD plus DTPA completely suppressed it, suggesting that RIF activated metal-dependent O2·(-)-mediated mechanisms producing ·OH inside tubercle bacilli. The finding that the metal chelator DTPA reduced the bactericidal activity of RIF supported the possibility that ·OH was generated through these mechanisms and that it participated at least in part in M. tuberculosis killing by the drug.

  8. Glutathione conjugation of busulfan produces a hydroxyl radical-trapping dehydroalanine metabolite.

    PubMed

    Peer, Cody J; Younis, Islam R; Leonard, Stephen S; Gannett, Peter M; Minarchick, Valerie C; Kenyon, Allison J; Rojanasakul, Yon; Callery, Patrick S

    2012-12-01

    The Phase 2 drug metabolism of busulfan yields a glutathione conjugate that undergoes a β-elimination reaction. The elimination product is an electrophilic metabolite that is a dehydroalanine-containing tripeptide, γ-glutamyldehydroalanylglycine (EdAG). In the process, glutathione lacks thiol-related redox properties and gains a radical scavenging dehydroalanine group. EdAG scavenged hydroxyl radical generated in the Fenton reaction in a concentration-dependent manner was monitored by electron paramagnetic resonance (EPR) spectroscopy. The apparent rate of hydroxyl radical scavenging was in the same range as published values for known antioxidants, including N-acyl dehydroalanines. A captodatively stabilized carbon-centered radical intermediate was spin trapped in the reaction of EdAG with hydroxyl radical. The proposed structure of a stable product in the Fenton reaction with EdAG was consistent with that of a γ-glutamylserylglycyl dimer. Observation of the hydroxyl trapping properties of EdAG suggests that the busulfan metabolite EdAG may contribute to or mitigate redox-related cytotoxicity associated with the therapeutic use of busulfan, and reaffirms indicators that support a role in free radical biology for dehydroalanine-containing peptides and proteins.

  9. Probing Hfq:RNA interactions with hydroxyl radical and RNase footprinting.

    PubMed

    Ellis, Michael J; Trussler, Ryan S; Ross, Joseph A; Haniford, David B

    2015-01-01

    RNA footprinting and structure probing techniques are used to characterize the interaction between RNA-binding proteins and RNAs in vitro. Hydroxyl radical footprinting results in the identification of protein binding site(s) in an RNA. Ribonuclease (RNase) structure probing is a complementary technique that also provides information about protein binding sites, as well as RNA structure and possible protein-directed RNA remodeling. Here we provide a comprehensive protocol for studying the interaction between Hfq and an mRNA or sRNA of interest using a combination of RNase A, T1, and V1 as well as hydroxyl radical footprinting techniques. Detailed protocols for in vitro synthesis of (32)P-labeled RNA; formation of Hfq:RNA binary complex(es), RNase, and hydroxyl radical footprinting; preparation and running of sequencing gels; and data analysis are provided.

  10. The hydroxyl radical scavenging effect of textile preparation auxiliaries on the photochemical treatment of nonylphenol ethoxylate.

    PubMed

    Arslan-Alaton, Idil; Shayin, Sarina; Olmez-Hanci, Tugba

    2012-01-01

    The present paper deals with the effects of frequently used textile preparation chemicals and common ions on the H2O2/UV-C treatment of a commercially important and slowly biodegradable nonionic surfactant, namely a nonylphenol bearing 10 ethoxylated chains. For this purpose, the effect of soda ash carbonate (0-5.0 g L(-1)), two phosphonic acid-based organic sequestering agents (0-2.5 g L(-1)) and chloride (0-3.0 g L(-1)) at two different pH values (3.5 and 10.5) as hydroxyl radical scavengers was experimentally investigated. Among the studied textile preparation chemicals and hydroxyl radical scavengers, the decreasing order of hydroxyl radical scavenging capacity was established as diethylene triamine pentamethylene phosphonic acid > 1-hydroxy ethylidene-1,1-diphosphonic acid > soda ash carbonate at pH 10.5 > chloride at pH 3.5 > chloride at pH 10.5.

  11. Hypersensitive radical probe studies of chloroperoxidase-catalyzed hydroxylation reactions.

    PubMed

    Toy, P H; Newcomb, M; Hager, L P

    1998-07-01

    The oxidation of hypersensitive radical probes by chloroperoxidase from Caldariomyces fumago (CPO) was studied in an attempt to "time" a putative radical intermediate. Oxidation of (trans-2-phenylcyclopropyl)methane, previously studied by Zaks and Dodds [Zaks, A., and Dodds, D. R. (1995) J. Am. Chem. Soc. 115, 10419-10424] was reinvestigated. Unrearranged oxidation products were found as previously reported, and control experiments demonstrated that the cyclic alcohol from oxidation at the cyclopropylcarbinyl position, while subject to further oxidation, survives CPO oxidation as detectable species. However, in contrast to the report by Zaks and Dodds, the rearranged alcohol product expected from ring opening of a cyclopropylcarbinyl radical intermediate was shown to be unstable toward the enzyme oxidation reaction. Because of this instability, two new hypersensitive radical probes, (trans-2-phenylcyclopropyl)ethane and 2-(trans-2-phenylcyclopropyl)propane, and their potential cyclic and acyclic products from oxidation at the cyclopropylcarbinyl position were synthesized and tested. Oxidation of both of these probes at the cyclopropylcarbinyl position by CPO gave unrearranged alcohol products only, but control experiments again demonstrated that the rearranged alcohol products were unstable toward CPO oxidation conditions. From the combination of the probe and control studies, the lifetime of a putative radical intermediate must be less than 3 ps. Whereas the results are consistent with an insertion mechanism for production of alcohol product, they do not exclude a very short-lived intermediate.

  12. Covalently bound fluorescent probes as reporters for hydroxyl radical penetration into liposomal membranes.

    PubMed

    Fortier, Chanel A; Guan, Bing; Cole, Richard B; Tarr, Matthew A

    2009-05-15

    The ability of hydroxyl radicals to penetrate into liposomal model membranes (dimyristoylphosphatidylcholine) has been demonstrated. Liposomes were prepared and then characterized by digital fluorescence microscopy and dynamic light scattering after extrusion to determine liposomal lamellarity, size, and shape. Hydroxyl radicals were generated in the surrounding aqueous medium using a modified Fenton reagent (hydrogen peroxide and Fe(2+)) with the water-soluble iron chelator EDTA. High and low doses of radical were used, and the low dose was achieved with physiologically relevant iron and peroxide concentrations. Fluorescent probes covalently bound to the membrane phospholipid were used, including two lipophilic pyrenyl probes within the membrane bilayer and one polar probe at the water-membrane interface. Radical reactions with the probes were monitored by following the decrease in fluorescence and by observing oxidation products via matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Differences in the probe position within the membrane were correlated with the reactivity of the probe to assess radical access to the site of the probe. For all probes, reaction rates increased with increasing temperature. Within the membrane bilayer, reaction rates were greater for the probe closest to the membrane-water interface. Cholesterol protected these probes from oxidation. Kinetic models, scavenger studies, and product identification studies indicated that hydroxyl radical reacted directly with the in-membrane probes without the mediation of a secondary radical.

  13. Cupric-amyloid beta peptide complex stimulates oxidation of ascorbate and generation of hydroxyl radical.

    PubMed

    Dikalov, Sergey I; Vitek, Michael P; Mason, Ronald P

    2004-02-01

    A growing body of evidence supports an important role for oxidative stress in the pathogenesis of Alzheimer's disease. Recently, a number of papers have shown a synergistic neurotoxicity of amyloid beta peptide and cupric ions. We hypothesized that complexes of cupric ions with neurotoxic amyloid beta peptides (Abeta) can stimulate copper-mediated free radical formation. We found that neurotoxic Abeta (1-42), Abeta (1-40), and Abeta (25-35) stimulated copper-mediated oxidation of ascorbate, whereas nontoxic Abeta (40-1) did not. Formation of ascorbate free radical was significantly increased by Abeta (1-42) in the presence of ceruloplasmin. Once cupric ion is reduced to cuprous ion, it can be oxidized by oxygen to generate superoxide radical or it can react with hydrogen peroxide to form hydroxyl radical. Hydrogen peroxide greatly increased the oxidation of cyclic hydroxylamines and ascorbate by cupric-amyloid beta peptide complexes, implying redox cycling of copper ions. Using the spin-trapping technique, we have shown that toxic amyloid beta peptides led to a 4-fold increase in copper-mediated hydroxyl radical formation. We conclude that toxic Abeta peptides do indeed stimulate copper-mediated oxidation of ascorbate and generation of hydroxyl radicals. Therefore, cupric-amyloid beta peptide-stimulated free radical generation may be involved in the pathogenesis of Alzheimer's disease.

  14. E.s.r. of spin-trapped radicals in aqueous solutions of peptides. Reactions of the hydroxyl radical.

    PubMed

    Joshi, A; Rustgi, S; Moss, H; Riesz, P

    1978-03-01

    The reactions of hydroxyl radicals with 30 dipeptides and several larger peptides were studied in aqueous solutions. The OH radicals were generated by U.V. photolysis of H2O2. The short-lived peptide radicals were spin-trapped using t-nitrosobutane and identified by e.s.r. For dipeptides containing the amino terminal residues glycine, alanine and phenylalanine, abstraction of the hydrogen from the carbon adjacent to the peptide nitrogen was the major process leading to the spin-adducts. Such radicals will be referred to as backbone radicals. Dipeptides with a carbonyl terminal serine residue and also glycylglutamic acid form both backbone and side-chain radicals, with the latter being formed in larger quantities. For dipeptides, side-chain radicals were detected on either the carboxyl or amino terminal residues of both. The effect of pD on the e.s.r. sectrum of the spin-adducts of glycylglycine was studied and the pK of the carboxyl group of this radical was determined to be 2.5. For (Ala)3 and (Ala)n, with an average value of n = 1800, backbone and minor side-chain radicals were observed. For ribonucleases-S-peptide, containing 20 amino acid residues, both backbone and side-chain radicals were detected.

  15. Theoretical study on the gas phase reaction of allyl chloride with hydroxyl radical

    NASA Astrophysics Data System (ADS)

    Zhang, Yunju; Chao, Kai; Sun, Jingyu; Zhang, Wanqiao; Shi, Haijie; Yao, Cen; Su, Zhongmin; Pan, Xiumei; Zhang, Jingping; Wang, Rongshun

    2014-02-01

    The reaction of allyl chloride with the hydroxyl radical has been investigated on a sound theoretical basis. This is the first time to gain a conclusive insight into the reaction mechanism and kinetics for important pathways in detail. The reaction mechanism confirms that OH addition to the C=C double bond forms the chemically activated adducts, IM1 (CH2CHOHCH2Cl) and IM2 (CH2OHCHCH2Cl) via low barriers, and direct H-abstraction paths may also occur. Variational transition state model and multichannel RRKM theory are employed to calculate the temperature-, pressure-dependent rate constants. The calculated rate constants are in good agreement with the experimental data. At 100 Torr with He as bath gas, IM6 formed by collisional stabilization is the major products in the temperature range 200-600 K; the production of CH2CHCHCl via hydrogen abstractions becomes dominant at high temperatures (600-3000 K).

  16. Ascorbate-dependent formation of hydroxyl radicals in the presence of iron chelates.

    PubMed

    Prabhu, H R; Krishnamurthy, S

    1993-10-01

    The autoxidation of L-ascorbate on incubation in saline phosphate buffer (pH 7.4) is accompanied by hydroxyl radical (.OH) generation. The metal chelator EDTA showed significant inhibition of ascorbate autoxidation and ascorbate-dependent .OH release. On the other hand, Fe2+ (EDTA) greatly augmented both ascorbate autoxidation and ascorbate-dependent .OH production. The biological iron chelating compounds such as ATP, ADP, citrate and pyrophosphate suppressed both ascorbate autoxidation and ascorbate-mediated .OH production, thereby indicating that these compounds suppress the activating effect of iron. Ascorbate autoxidation and ascorbate-dependent .OH formation, stimulated by Fe2+ (EDTA) were significantly inhibited by .OH scavengers, namely mannitol, thiourea and sodium formate, as well as by catalase and to a lesser extent by bovine serum albumin, superoxide dismutase (native and heat denatured) and heat denatured catalase.

  17. Hydroxyl radicals from secondary organic aerosol decomposition in water

    NASA Astrophysics Data System (ADS)

    Tong, Haijie; Arangio, Andrea M.; Lakey, Pascale S. J.; Berkemeier, Thomas; Liu, Fobang; Kampf, Christopher. J.; Pöschl, Ulrich; Shiraiwa, Manabu

    2016-04-01

    We found that ambient and laboratory-generated secondary organic aerosols (SOA) form substantial amounts of OH radicals upon interaction with liquid water, which can be explained by the decomposition of organic hydroperoxides. The molar OH yield from SOA formed by ozonolysis of terpenes (α-pinene, β-pinene, and limonene) is ~ 0.1% upon extraction with pure water, and which increases to ~ 1.5% in the presence of iron ions due to Fenton-like reactions. Our findings imply that the chemical reactivity and aging of SOA particles is strongly enhanced upon interaction with water and iron. In cloud droplets under dark conditions, SOA decomposition can compete with the classical hydrogen peroxide Fenton reaction as the source of OH radicals. Also in the human respiratory tract, the inhalation and deposition of SOA particles may lead to a substantial release of OH radicals, which may contribute to oxidative stress and play an important role in the adverse health effects of atmospheric aerosols.

  18. Hydroxyl radicals from secondary organic aerosol decomposition in water

    NASA Astrophysics Data System (ADS)

    Tong, Haijie; Arangio, Andrea M.; Lakey, Pascale S. J.; Berkemeier, Thomas; Liu, Fobang; Kampf, Christopher J.; Brune, William H.; Pöschl, Ulrich; Shiraiwa, Manabu

    2016-02-01

    We found that ambient and laboratory-generated secondary organic aerosols (SOA) form substantial amounts of OH radicals upon interaction with liquid water, which can be explained by the decomposition of organic hydroperoxides. The molar OH yield from SOA formed by ozonolysis of terpenes (α-pinene, β-pinene, limonene) is ˜ 0.1 % upon extraction with pure water and increases to ˜ 1.5 % in the presence of Fe2+ ions due to Fenton-like reactions. Upon extraction of SOA samples from OH photooxidation of isoprene, we also detected OH yields of around ˜ 0.1 %, which increases upon addition of Fe2+. Our findings imply that the chemical reactivity and aging of SOA particles is strongly enhanced upon interaction with water and iron. In cloud droplets under dark conditions, SOA decomposition can compete with the classical H2O2 Fenton reaction as the source of OH radicals. Also in the human respiratory tract, the inhalation and deposition of SOA particles may lead to a substantial release of OH radicals, which may contribute to oxidative stress and play an important role in the adverse health effects of atmospheric aerosols.

  19. Hydroxyl radicals from secondary organic aerosol decomposition in water

    NASA Astrophysics Data System (ADS)

    Tong, H.; Arangio, A. M.; Lakey, P. S. J.; Berkemeier, T.; Liu, F.; Kampf, C. J.; Pöschl, U.; Shiraiwa, M.

    2015-11-01

    We found that ambient and laboratory-generated secondary organic aerosols (SOA) form substantial amounts of OH radicals upon interaction with liquid water, which can be explained by the decomposition of organic hydroperoxides. The molar OH yield from SOA formed by ozonolysis of terpenes (α-pinene, β-pinene, limonene) is ~ 0.1 % upon extraction with pure water and increases to ~ 1.5 % in the presence of Fe2+ ions due to Fenton-like reactions. Our findings imply that the chemical reactivity and aging of SOA particles is strongly enhanced upon interaction with water and iron. In cloud droplets under dark conditions, SOA decomposition can compete with the classical H2O2 Fenton reaction as the source of OH radicals. Also in the human respiratory tract, the inhalation and deposition of SOA particles may lead to a substantial release of OH radicals, which may contribute to oxidative stress and play an important role in the adverse health effects of atmospheric aerosols.

  20. HYDROXYL RADICAL/OZONE RATIOS DURING OZONATION PROCESSES. I. THE RCT CONCEPT

    EPA Science Inventory

    The ozonation of model systems and several natural waters was examined in bench-scale batch experiments. In addition to measuring the concentration of ozone (03), the rate of depletion of an in situ hydroxyl radical probe compound was monitored, thus providing information on the ...

  1. [Study on the spectrophotometric determination of hydroxyl free radical from low power trench-type ultrasound].

    PubMed

    Cao, Yan-ping; Yuan, Ying-mao; Zhu, Yu-chen

    2012-05-01

    Under the condition of different pH (7-11) and different ethanol volume fraction (45% to 85%), the ultraviolet-visible absorption spectra of malachite green were studied in neutral and alkaline ethanol solution, the maximum absorption wavelength at 620 nm was found, and the matching degree of standard curve was better established. In low power trench-type ultrasound apparatus, the absorption of the malachite green solution was measured under ultrasound and non-ultrasound, respectively. the difference values of the ultraviolet absorption of the malachite green solution under low power trench-type ultrasound were measured results of the hydroxyl free radical oxidation degrading malachite green, therefore hydroxyl free radical from low power trench-type ultrasound was determined indirectly. Then the contents of hydroxyl free radical in four conditions were measured. The detection limit of the method of 8.4 x 10(-6) mmol x L(-1) and the relative standard deviation of the method of 9.4 x 10(-5) - 3.7 x 10(-4) mmol x L(-1) were determined, a higher testing precision and good reproducibility were confirmed. It can be applied for fast detection of neutral and alkaline ethanol solution system in the case of very low concentration of hydroxyl free radicals. Since malachite green is heat sensitive, so compared to measuring temperature, the method possessed better functions for thermal effects of ultrasound.

  2. PHOTOCHEICAL PRODUCTION OF HYDROXYL RADICAL IN NATURAL WATER - THE ROLE OF IRON AND DISSOLVED ORGANIC MATTER

    EPA Science Inventory

    Photochemical hydroxyl radical (OH) production was measured in several natural waters to investigate the importance of colored dissolved organic matter (CDOM) and iron-CDOM complexes as sources of OH. High rates of OH photoproduction in highly colored, iron-rich, acidic waters a...

  3. RELATIVE RATE CONSTANTS OF CONTAMINANT CANDIDATE LIST PESTICIDES WITH HYDROXYL RADICALS

    EPA Science Inventory

    The objective of this study was to establish the rate constants for the reactions of selected pesticides listed on the US EPA Contaminant Candidate List, with UV and hydroxyl radicals (·OH). Batch experiments were conducted in phosphate buffered solution at pH 7. All pestici...

  4. Rovibrational intensities and electric dipole moment function of the X2 Pi hydroxyl radical

    NASA Technical Reports Server (NTRS)

    Chackerian, C., Jr.; Goorvitch, D.; Benidar, A.; Farrenq, R.; Guelachvili, G.; Martin, P. M.; Abrams, M. C.; Davis, S. P.

    1992-01-01

    Recent work aimed at determining the absolute rovibrational transition intensities for the ground electronic state of the hydroxyl radical is reviewed. Two new sets of Fourier transform emission spectra of OH are described which were recorded at the University of Paris and at the Kitt Peak National Solar Observatory.

  5. Methyl-esterified 3-hydroxybutyrate oligomers protect bacteria from hydroxyl radicals

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bacteria rely mainly on enzymes, glutathione and other low-molecular weight thiols to overcome oxidative stress. However, hydroxyl radicals are the most cytotoxic reactive oxygen species, and no known enzymatic system exists for their detoxification. We now show that methyl-esterified dimers and tri...

  6. Characterization of the reaction rate coefficient of DNA with the hydroxyl radical

    SciTech Connect

    Milligan, J.R.; Ward, J.F.; Aguilera, J.A.

    1996-11-01

    Using agarose gel electrophoresis, we have measured the yield of single-strand breaks (SSBs) induced by {sup 137}Cs {gamma} irradiation in a variety of plasmid DNA substrates ranging in size from 2.7 kb to 38 kb irradiated in aerobic aqueous solution in the presence of the hydroxyl radical scavenger dimethyl sulfoxide (DMSO). Under these conditions DNA SSBs are caused mainly by the hydroxyl radical. Using the competition between DMSO and DNA for the hydroxyl radical, we have estimated the rate coefficient for the reaction of the hydroxyl radical with DNA. The results cannot be characterized by conventional steady-state competition kinetics. However, it is possible to describe the second-order rate constant for the reaction as a function of the scavenging capacity of the solution. The second-order rate constant increases with increasing scavenging capacity, rising from about 5x10{sup 8} dm{sup 3} mol{sup -1} s{sup -1} at 10{sup 5} s{sup -1} to about 10{sup 10} dm{sup 3} mol{sup -1} s{sup -1} at 10{sup 10} s{sup -1}. This dependence of the second-order rate constant on the scavenging capacity appears to be more pronounced for larger plasmids. 17 refs., 4 figs.

  7. A new mechanism for hydroxyl radical production in irradiated nanoparticle solutions.

    PubMed

    Sicard-Roselli, Cécile; Brun, Emilie; Gilles, Manon; Baldacchino, Gérard; Kelsey, Colin; McQuaid, Harold; Polin, Chris; Wardlow, Nathan; Currell, Frederick

    2014-08-27

    The absolute yield of hydroxyl radicals per unit of deposited X-ray energy is determined for the first time for irradiated aqueous solutions containing metal nanoparticles based on a "reference" protocol. Measurements are made as a function of dose rate and nanoparticle concentration. Possible mechanisms for hydroxyl radical production are considered in turn: energy deposition in the nanoparticles followed by its transport into the surrounding environment is unable to account for observed yield whereas energy deposition in the water followed by a catalytic-like reaction at the water-nanoparticle interface can account for the total yield and its dependence on dose rate and nanoparticle concentration. This finding is important because current models used to account for nanoparticle enhancement to radiobiological damage only consider the primary interaction with the nanoparticle, not with the surrounding media. Nothing about the new mechanism appears to be specific to gold, the main requirements being the formation of a structured water layer in the vicinity of the nanoparticle possibly through the interaction of its charge and the water dipoles. The massive hydroxyl radical production is relevant to a number of application fields, particularly nanomedicine since the hydroxyl radical is responsible for the majority of radiation-induced DNA damage.

  8. Scavenging of hydroxyl radical by resveratrol and related natural stilbenes after hydrogen peroxide attack on DNA.

    PubMed

    Rossi, Miriam; Caruso, Francesco; Antonioletti, Roberto; Viglianti, Angela; Traversi, Gianandrea; Leone, Stefano; Basso, Emiliano; Cozzi, Renata

    2013-11-25

    Resveratrol (3,5,4'-trihydroxystilbene) is of interest due to its role in prevention and therapy of degenerative diseases as cancer and aging. However, depending on its concentration and cell type studied, resveratrol activity appears conflicting. It exerts antioxidant action, as a scavenger of free radicals and as promoter of antioxidant enzyme activity, but resveratrol acts also as a pro-oxidant. Here we present experimental and theoretical studies for resveratrol and two methoxy-derivatives found in plants, pterostilbene and 3,5,4'-trimethoxystilbene. We show that both methoxy-derivatives induce less DNA damage than resveratrol. The protective effects of the three molecules against oxidative DNA damage induced by hydrogen peroxide treatment were analyzed on mammalian cells in vitro. Our data show for the first time that methoxylated derivatives of resveratrol are very efficient in reducing DNA damage: using the same concentration of the three molecules we obtain a relative reduction of 85.5% (pterostilbene), 43.7% (trimethoxystilbene) and 21.1% (resveratrol). Analysis of the crystal structures of pterostilbene and 3,5,4'-trimethoxystilbene, compared to resveratrol, show fewer intermolecular interactions and a lack of planarity, due to packing forces, which is confirmed by density functional theory (DFT) calculations. We also describe the results of DFT calculations (including water solvent effects) in which the three stilbene species scavenge the hydroxyl radical (associated with the H2O2 insult).

  9. Theoretical study of the oxidation mechanisms of thiophene initiated by hydroxyl radicals.

    PubMed

    Shiroudi, Abolfazl; Deleuze, Michael S

    2015-11-01

    The mechanisms for the oxidation of thiophene by OH radicals under inert conditions (Ar) have been studied using density functional theory in conjunction with various exchange-correlation functionals. These results were compared with benchmark CBS-QB3 theoretical results. Kinetic rate constants were estimated by means of variational transition state theory (VTST) and the statistical Rice-Ramsperger-Kassel-Marcus (RRKM) theory. Effective rate constants were calculated via a steady-state analysis based upon a two-step model reaction mechanism. In line with experimental results, the computed branching ratios indicate that the most kinetically efficient process involves OH addition to a carbon atom adjacent to the sulfur atom. Due to the presence of negative activation energies, pressures larger than 10(4) bar are required to reach the high-pressure limit. Nucleus-independent chemical shift indices and natural bond orbital analysis show that the computed activation energies are dictated by changes in aromaticity and charge-transfer effects due to the delocalization of lone pairs from sulfur to empty π(*) orbitals. Graphical Abstract CBS-QB3 energy profiles for the reaction pathways 1-3 characterizing the oxidation of thiophene by hydroxyl radicals into the related products.

  10. EPR detection of hydroxyl radical generation and its interaction with antioxidant system in Carassius auratus exposed to pentachlorophenol.

    PubMed

    Luo, Yi; Wang, Xiao-rong; Ji, Liang-liang; Su, Yan

    2009-11-15

    In the present study, direct evidence of hydroxyl radical production in livers of Carassius auratus exposed to pentachlorophenol (PCP) was provided using electron paramagnetic resonance (EPR) with spin-trapping. A dose-effect relationship was obtained between hydroxyl radical intensities and PCP exposure. It was observed that hydroxyl radical was significantly induced by 0.001 mg l(-1) (below the criteria for Chinese fishery water quality) of PCP exposure. A strong positive correlation (r=0.9581, p<0.001) was observed between PCP liver concentrations and hydroxyl radical intensities within 7d of PCP exposure, which suggests that hydroxyl radical are mainly produced from PCP itself. However, no correlation was observed between PCP liver concentrations and hydroxyl radical intensities after 7d, and a higher intensity of hydroxyl radical could still be observed when the PCP liver concentrations decreased to a lower level, which suggests that other mechanisms may possibly contribute to hydroxyl radical production after 7d. The glutathione/oxidized glutathione (GSH/GSSG) ratio decreased below that of the control level during the entire period of PCP exposure (0.05 mg l(-1)), which suggested oxidative stress occurred.

  11. Arbutin, an intracellular hydroxyl radical scavenger, protects radiation-induced apoptosis in human lymphoma U937 cells.

    PubMed

    Wu, Li-Hua; Li, Peng; Zhao, Qing-Li; Piao, Jin-Lan; Jiao, Yu-Fei; Kadowaki, Makoto; Kondo, Takashi

    2014-11-01

    Ionizing radiation (IR) can generate reactive oxygen species (ROS). Excessive ROS have the potential to damage cellular macromolecules including DNA, proteins, and lipids and eventually lead to cell death. In this study, we evaluated the potential of arbutin, a drug chosen from a series of traditional herbal medicine by measuring intracellular hydroxyl radical scavenging ability in X-irradiated U937 cells. Arbutin (hydroquinone-β-D-glucopyranoside), a naturally occurring glucoside of hydroquinone, has been traditionally used to treat pigmentary disorders. However, there are no reports describing the effect of arbutin on IR-induced apoptosis. We confirmed that arbutin can protect cells from apoptosis induced by X-irradiation. The combination of arbutin and X-irradiation could reduce intracellular hydroxyl radical production and prevent mitochondrial membrane potential loss. It also could down-regulate the expression of phospho-JNK, phospho-p38 in whole cell lysate and activate Bax in mitochondria. Arbutin also inhibits cytochrome C release from mitochondria to cytosol. To verify the role of JNK in X-irradiation-induced apoptosis, the cells were pretreated with a JNK inhibitor, and found that JNK inhibitor could reduce apoptosis induced by X-irradiation. Taken together, our data indicate that arbutin plays an anti-apoptotic role via decreasing intracellular hydroxyl radical production, inhibition of Bax-mitochondria pathway and activation of the JNK/p38 MAPK pathway.

  12. Monitoring equilibrium changes in RNA structure by 'peroxidative' and 'oxidative' hydroxyl radical footprinting.

    PubMed

    Bachu, Ravichandra; Padlan, Frances-Camille S; Rouhanifard, Sara; Brenowitz, Michael; Schlatterer, Jörg C

    2011-10-17

    RNA molecules play an essential role in biology. In addition to transmitting genetic information, RNA can fold into unique tertiary structures fulfilling a specific biologic role as regulator, binder or catalyst. Information about tertiary contact formation is essential to understand the function of RNA molecules. Hydroxyl radicals (•OH) are unique probes of the structure of nucleic acids due to their high reactivity and small size. When used as a footprinting probe, hydroxyl radicals map the solvent accessible surface of the phosphodiester backbone of DNA and RNA with as fine as single nucleotide resolution. Hydroxyl radical footprinting can be used to identify the nucleotides within an intermolecular contact surface, e.g. in DNA-protein and RNA-protein complexes. Equilibrium and kinetic transitions can be determined by conducting hydroxyl radical footprinting as a function of a solution variable or time, respectively. A key feature of footprinting is that limited exposure to the probe (e.g., 'single-hit kinetics') results in the uniform sampling of each nucleotide of the polymer. In this video article, we use the P4-P6 domain of the Tetrahymena ribozyme to illustrate RNA sample preparation and the determination of a Mg(II)-mediated folding isotherms. We describe the use of the well known hydroxyl radical footprinting protocol that requires H(2)O(2) (we call this the 'peroxidative' protocol) and a valuable, but not widely known, alternative that uses naturally dissolved O(2)(we call this the 'oxidative' protocol). An overview of the data reduction, transformation and analysis procedures is presented.

  13. Inhibition of hydroxyl radical reaction with aromatics by dissolved natural organic matter

    SciTech Connect

    Lindsey, M.E.; Tarr, M.A.

    2000-02-01

    Remediation of hydrophobic pollutants is complicated by sorption of these compounds to hydrophobic sites of dissolved natural organic matter (NOM), suspended particulates, soil, and sediment. This sorption causes the pollutants to be less easily degraded by remediation techniques. Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compound molecules bound to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H{sub 2}O{sub 2} + Fe{sup 2+} {yields} Fe{sup 3+} + HO{sup {minus}} + HO{sm_bullet}). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanism for the observed inhibition is that hydroxyl radical formation occurs in microenvironmental sites remote from the aromatic compounds. In addition to changes in kinetics, pyrene hydroxyl radical reaction also exhibited a mechanistic change in the presence of fulvic acid. The mechanism changed from a reaction that was apparently first-order in pyrene to one that was apparently second-order in pyrene, indicating that pyrene self-reaction may have become the dominant mechanism in the presence of fulvic acid. Dissolved NOM causes significant changes in the rate and mechanism of hydroxyl radical degradation of aromatic compounds. Consequently, literature rate constants measured in pure water will not be useful for predicting the degradation of pollutants in environmental systems. The kinetic and mechanistic information in this study will be useful for developing improved degradation methods involving Fenton chemistry.

  14. Tropospheric reactions of the haloalkyl radicals formed from hydroxyl radical reaction with a series of alternative fluorocarbons

    NASA Technical Reports Server (NTRS)

    Atkinson, Roger

    1990-01-01

    In the present assessment, the hydrogen containing halocarbons being considered as alternatives to the the presently used chlorofluorocarbons are the hydrochlorofluorocarbons (HCFCs) 123 (CF3CHCl2), 141b (CFCl2CH3), 142b (CF2ClCH3), 22 (CHF2Cl) and 124 (CF3CHFCl) and the hydrofluorocarbons (HFCs) 134a (CF3CH2F), 152a (CHF2CH3) and 125 (CF3CHF2). All of these HCFCs and HFCs will react with the hydroxyl (OH) radical in the troposphere, giving rise to haloalkyl radicals which then undergo a complex series of reactions in the troposphere. These reactions of the haloalkyl radicals formed from the initial OH radical reactions with the HCFCs and HFCs under tropospheric conditions are the focus here.

  15. Mechanism of hydroxyl radical generation from biochar suspensions: Implications to diethyl phthalate degradation.

    PubMed

    Fang, Guodong; Zhu, Changyin; Dionysiou, Dionysios D; Gao, Juan; Zhou, Dongmei

    2015-01-01

    This paper investigated hydroxyl radical (OH) generation from biochar suspensions for diethyl phthalate (DEP) degradation in the presence of oxygen. Electron paramagnetic resonance (EPR) coupled with a salicylic acid trapping method were used to detect free radicals in biochar and verify OH generation from biochar suspensions. Free radicals (FRs) in biochar could induce OH generation, and ≈12 spins of FRs were consumed to produce one trapped [OH] molecule. The proposed mechanism of OH generation was that FRs in biochar transferred electrons to O2 to produce the superoxide radical anion and hydrogen peroxide, which reacted further with FRs to produce OH. Free radical-quenching studies utilizing superoxide dismutase, catalase, and deferoxamine as scavengers were used to testify this mechanism. Furthermore, OH generated from biochar suspensions could degrade DEP efficiently. These findings of this study provide new insights into the physicochemical properties and environmental implications of biochar.

  16. Radiation-induced cell lethality of samonella typhimurium ATCC 14028: Cooperative effect of hydroxyl radical and oxygen

    SciTech Connect

    Kim, Y.A.; Thayer, D.W.

    1995-10-01

    The lethality of {gamma}-radiation doses of 0.2 to 1.0 kGy for Salmonella typhimurium ATCC 14028 was measured in the presence of air, N{sub 2} and N{sub 2}O and with the hydroxyl radical scavengers formate and polyethylene glycol (PEG), M{sub r} 8,000. Saturation of cell suspensions with either N{sub 2}O or N{sub 2}/N{sub 2}/N{sub 2}O (1:1, v/v) gas was expected to double the number of hydroxyl radicals (OH{center_dot}) and to produce an equivalent increase in lethality, but this did not occur. Adding 10% (v/v) O{sub 2} to either N{sub 2}/N{sub 2}O gas produced approximately the same {gamma}-irradiation lethality for S. typhimurium as did air. Addition of hydroxyl radical scavengers, 40 mM formate and 1.5% (w/v) PEG, significantly reduced the lethality of {gamma} radiation for S. typhimurium in the presence of air but not in the presence of N{sub 2} or N{sub 2}O gases. Membrane-permeable formate provided slightly better protection than nonpermeable PEG. Cells of S. typhimurium grown under anaerobic conditions were more sensitive to radiation, and were less protected by hydroxyl radical scavengers, especially formate, than when cells grown under aerobic conditions were irradiated in the presence of oxygen. Hydroxyl radical scavengers provided no further protection during irradiation in the absence of oxygen. These results indicated that the increased radiation sensitivity of cells grown under anaerobic conditions may be related to superoxide radicals which could increase intercellular damage during irradiation in the presence of oxygen. However, endogenous superoxide dismutase and catalase activities did not protect cells from the radiation-induced lethality of S. typhimurium. Cytoplasmic extracts protected bacterial DNA in vitro in either the presence of absence of oxygen, and no radiation-induced lipid peroxidation of the cellular components was identified by measuring the levels of 2-thiobarbituric acid. 38 refs., 4 figs., 2 tabs.

  17. Intracellular-produced hydroxyl radical mediates H2O2-induced Ca2+ influx and cell death in rat beta-cell line RIN-5F.

    PubMed

    Ishii, Masakazu; Shimizu, Shunichi; Hara, Yuji; Hagiwara, Tamio; Miyazaki, Akira; Mori, Yasuo; Kiuchi, Yuji

    2006-06-01

    The melastatin-related transient receptor potential channel TRPM2 is a Ca(2+)-permeable channel that is activated by H(2)O(2), and the Ca(2+) influx through TRPM2 mediates cell death. However, the responsible oxidants for TRPM2 activation remain to be identified. In the present study, we investigated the involvement of hydroxyl radical on TRPM2 activation in TRPM2-expressing HEK293 cells and the rat beta-cell line RIN-5F. In both cell types, H(2)O(2) induced Ca(2+) influx in a concentration-dependent manner. However, the addition of hydroxyl radical, which was produced by mixing FeSO(4) and H(2)O(2), to the cells, did not increase intracellular Ca(2+) concentration. Interestingly, when H(2)O(2) was added to the cells under intracellular Fe(2+)-accumulated conditions, Ca(2+) influx was markedly enhanced compared to H(2)O(2) alone. In addition, the H(2)O(2)-induced Ca(2+) influx was reduced by hydroxyl radical scavengers and an iron chelator. Under intracellular Fe(2+)-accumulated conditions, H(2)O(2)-induced RIN-5F cell death through TRPM2 activation was also markedly enhanced. Hydroxyl radical scavengers and an iron chelator suppressed the RIN-5F cell death by H(2)O(2). These results strongly suggest that the intracellular hydroxyl radical plays a key role in the activation of TRPM2 during H(2)O(2) treatment, and TRPM2 activation mediated by hydroxyl radical is implicated in H(2)O(2)-induced cell death in the beta-cell line RIN-5F.

  18. Hydroxyl radical (OH) scavenging in young and mature landfill leachates.

    PubMed

    Ghazi, Niloufar M; Lastra, Andres A; Watts, Michael J

    2014-06-01

    The final discharge point for collected landfill leachates is frequently the local municipal wastewater treatment facility. The salinity, color, nutrient, and anthropogenic organics contamination of leachates often necessitate some form of pre-treatment. When advanced oxidation processes (AOPs) are considered for pre-treatment, the unique composition of dissolved organic matter (DOM) and the relatively high concentrations of some inorganic solutes in leachate will inhibit treatment efficiency. The most important benchmark for design of AOPs is the expected steady-state production of free radical (OH). Without a quantitative assessment of total OH consumption in high-strength waste water, like a landfill leachate, efficient AOP treatment is uncertain. For this reason, two landfill leachates, distinct in color, DOM, and age of landfill, were characterized for OH-scavenging using an established competition kinetics method. After stripping the samples of inorganic carbon, the DOM in leachate from mature (stabilized) landfill was found to react with OH at a rate of 9.76 × 10(8) M(-1)s(-1). However, DOM in leachate from newer landfill was observed to scavenge available OH at a faster rate (8.28 × 10(9) M(-1)s(-1)). The combination of fast rate of reaction with OH and abundance of DOM in the sampled leachate severely limited the contribution of OH to degradation of an O3- and OH-labile organic probe compound (bisphenol-a) in oxidized mature leachate (fOH = 0.03). Substantial dosing of both O3 and H2O2 (>70 mg/L and >24 mg/L, respectively) may be required to see at least 1-log-removal (>90%) of an OH-selective leachate contaminant (i.e., parachlorobenzoic acid) in a mature landfill leachate.

  19. The Collisional and Radiative Processes of the Hydroxyl Radical

    NASA Astrophysics Data System (ADS)

    Steffens, Kristen Lisa

    1995-01-01

    The OH radical is an important species in the chemistry of atmospheric and combustion environments, where an understanding of OH concentration and chemistry is necessary to create and validate chemical models. Laser-induced fluorescence (LIF) is used with great success in OH detection, but OH LIF measurements require a vast knowledge of the collisional and spectroscopic properties of OH. Information is still lacking, especially concerning vibrational levels v^' > 0 of the rm A^2Sigma^+ electronic state. We investigate transition probabilities and collisional processes of these higher vibrational levels. Experimental vibrational band transition probabilities from v^' = 3 and 2 of OH rm A^2Sigma^+ are needed to determine the electronic transition moment for the rm A^2Sigma^+ -rm X^2Pi_{i } system to calculate a consistent set of rotational and vibrational dependent transition probabilities for uses including rm X^2Pi_ {i} temperature determinations and rm A^2Sigma^+ and rm X^2Pi_{i} nascent population determinations. Using LIF in a low -pressure CH_4/O_2 flame, we measured relative emission intensities for vibrational bands (3,0) through (3,5) and (2,0) through (2,6). Our emission intensities have been used in another study to determine the best rm A^2 Sigma^+-rm X^2 Pi_{i} electronic transition moment. For quantitative OH concentration measurements in high pressure flames exciting the predissociative v ^' = 3 level, one must account for vibrational energy transfer (VET). We measure the amounts of VET occurring from v^' = 3 in CH_4/O_2 , CH_4/air, and H _2/O_2 flames at pressures between 14 and 760 Torr. Significant amounts of VET occur in all flames and must be accounted for to get accurate OH concentrations. Stratospheric OH concentration measurement employs OH rm A^2Sigma^+v ^' = 1 excitation, which requires accurate VET and quenching cross sections for major colliders. We use LIF to measure the v^ ' = 1 VET and quenching cross sections for N_2, O_2 and CO_2

  20. Oxidation of carboxylic acids regenerates hydroxyl radicals in the unpolluted and nighttime troposphere.

    PubMed

    da Silva, Gabriel

    2010-07-01

    The hydroxyl radical (OH) controls the removal of organic compounds from the troposphere. Atmospheric chemistry models significantly under-predict OH levels in unpolluted environments, implying that they are regenerated via some unknown mechanism(s). This work uses computational chemistry to demonstrate that the photochemical oxidation of alkyl carboxylic acids can efficiently regenerate the hydroxyl radical via unimolecular decomposition of alpha-carboxyalkylperoxy radicals. For acetic acid and propanoic acid the proposed mechanism is predicted to dominate in the unpolluted lower troposphere, and it may also operate to some extent in the mid to upper troposphere. Alkyl carboxylic acids are also predicted to act as a new source of nighttime OH throughout the planetary boundary layer, where OH levels are also under-predicted. The thermodynamic requirements for reactions of this class are discussed, and some candidate OH-reforming molecules particularly relevant to aromatic photooxidation are identified. Adopting a broader perspective, the alpha-carboxyalkyl radical precursors that react with O(2) to form the unstable alpha-carboxyalkylperoxy type radicals are also expected to form during combustion, in the interstellar medium, and from the gamma-irradiation of glycine and related amino acids, and the potential importance of this new chemistry in these environments is discussed. Master equation simulations suggest that alpha-carboxyalkyl + O(2) reactions provide a prompt OH source during the autoignition and combustion of biodiesel and other oxygenated biofuels, where carboxylic acids are formed as early stage oxidation products. Ketene combustion is also thought to proceed via these OH-reforming alpha-carboxyalkyl radicals. The in vivo formation of alpha-carboxyalkylperoxy radicals followed by oxidation to the highly reactive OH radical may induce oxidative stress in the human body, in a process initiated by gamma-rays. Finally, the reaction of ketenes with OH to

  1. Reactions of hydroxyl radicals with alkenes in low-temperature matrices

    NASA Astrophysics Data System (ADS)

    Feltham, Emma J.; Almond, Matthew J.; Marston, George; Wiltshire, Karen S.; Goldberg, Nicola

    2000-11-01

    The reactions of hydroxyl radicals with a number of stable alkenes have been studied in low-temperature matrices. The reactions were initiated by broad band UV-visible irradiation of matrices containing H 2O 2 and the alkene under investigation. The hydroxyalkyl radical products were identified principally by comparison of their spectra with the spectra of corresponding stable alcohols. Accordingly, IR spectra were recorded for the following series of alcohols isolated in argon matrices — methanol, ethanol, ethanol- d6, propan-1-ol, propan-2-ol, butan-2-ol, 2-methylpropan-1-ol ( iso-butyl alcohol), 2-methylpropan-2-ol ( tert-butyl alcohol), 2-methylbutan-2-ol ( tert-amyl alcohol), 3-methylbutan-2-ol and 2,3-dimethylbutan-2-ol. The hydroxyalkyl radicals, which appear to be formed from the alkenes studied were as follows — from ethene, 2-hydroxyethyl radical; from cis- or trans-but-2-ene, 1-methyl-2-hydroxypropyl radical; from propene, 1-methyl-2-hydroxyethyl and 2-hydroxypropyl radicals; from but-1-ene, 1-hydroxymethylpropyl and 2-hydroxybutyl radicals; from 2-methylpropene ( iso-butene), 1,1-dimethyl-2-hydroxyethyl and 2-methyl-2-hydroxypropyl radicals; the radical products from buta-1,3-diene and isoprene could not be identified. In the cases, where two radical products were possible, i.e. when propene, but-1-ene or 2-methylpropene were the substrates, it was found that the concentration of the secondary or tertiary radical always exceeded that of the primary radical. However, the relative concentration of these radicals appears to be determined by subsequent photolysis to give carbonyl compounds. There seems, therefore, to be little preference for the secondary and tertiary radicals over the primary radicals in the primary addition process. Comments on the mechanism of the transformation from radical to carbonyl compound based upon identification of intermediates within the matrix and isotopic substitution experiments are made. The characterisation of the 2

  2. Bactericidal effect of colistin on planktonic Pseudomonas aeruginosa is independent of hydroxyl radical formation.

    PubMed

    Brochmann, Rikke Prejh; Toft, Anders; Ciofu, Oana; Briales, Alejandra; Kolpen, Mette; Hempel, Casper; Bjarnsholt, Thomas; Høiby, Niels; Jensen, Peter Østrup

    2014-02-01

    The bactericidal effect of several major types of antibiotics has recently been demonstrated to be dependent on the formation of toxic amounts of hydroxyl radicals (OH·) resulting from oxidative stress in metabolically active cells. Since killing by the antimicrobial peptide colistin does not require bacterial metabolic activity, we tested whether the bactericidal effect of colistin depends on the formation of OH·. In Pseudomonas aeruginosa cultures, OH-mediated killing by ciprofloxacin was demonstrated by decreased bacterial survival and induction of 3'-(p-hydroxyphenyl) fluorescein (HPF) fluorescence. OH·-mediated killing by ciprofloxacin was further confirmed by rescue of cells and reduction of HPF fluorescence due to prevention of OH· accumulation by scavenging with thiourea, by chelating with dipyridyl, by decreasing metabolism as well as by anoxic growth. In contrast, no formation of OH· was seen in P. aeruginosa during killing by colistin, and prevention of OH· accumulation could not rescue P. aeruginosa from killing by colistin. These results therefore demonstrate that the bactericidal activity of colistin on P. aeruginosa is not dependent on oxidative stress. In conclusion, antimicrobial peptides that do not rely on OH· formation should be considered for treatment of Gram-negative bacteria growing at low oxygen tension such as in endobronchial mucus and paranasal sinuses in cystic fibrosis patients, in abscesses and in infectious biofilm.

  3. Temperature dependence of the photochemical formation of hydroxyl radical from dissolved organic matter.

    PubMed

    McKay, Garrett; Rosario-Ortiz, Fernando L

    2015-04-07

    The temperature dependence of the photochemical production of the hydroxyl radical (•OH) from dissolved organic matter (DOM) was investigated by measuring the apparent temperature dependence of the quantum yield (Φa) for this process. Temperature dependent Φa values were analyzed using the Arrhenius equation. Apparent activation energies obtained for DOM isolates purchased from the International Humic Substances Society ranged from 16 to 34 kJ mol(-1). Addition of 40 units mL(-1) catalase, used to hinder the hydrogen peroxide (H2O2)-dependent pathway to •OH, did not impact the observed activation energy. However, an increase in activation energy was observed in lower molecular weight DOM obtained by size fractionation. We also measured the temperature dependence of p-benzoquionone photolysis as a model compound for DOM and observed no temperature dependence (slope p = 0.41) for the formation of phenol from oxidation of benzene (the •OH probe used), but a value of about 10 kJ mol(-1) for p-benzoquinone loss, which is consistent with formation of a quinone-water exciplex. These data provide insight into DOM photochemistry as well as provide parameters useful for modeling steady state •OH concentrations in natural systems.

  4. [Studies on the oxidation of tyrosine induced by hydroxyl radical with fluorescence spectroscopic method].

    PubMed

    Sun, Yan-hui; Wang, Wei-long; Wu, Lin-sheng; Jia, Xiao-li

    2011-07-01

    Dityrosine is a marker of tyrosine oxidation. To study effecting factors of hydroxyl radical on tyrosine oxidation, synchronous fluorescence spectra with two dimensional correlation was used. The results showed that the peak position and intensity of dityrosine changed while pH value varied. In the system of tyrosine oxidation, with the increment of tyrosine concentration, the concentration of dityrosine decreased. With the increment of hydrogen peroxide concentration, the concentration of dityrosine increased. The oxidation reaction was prone to taking place in acid conditions while difficult to develop in basic conditions. With the development of oxidation reaction, the fluorescence intensity of dityrosine increased and then decreased. Two dimentional correlation synchronous fluorescence spectra showed that the variation in the intensity at 292 nm preceded that of 281, 300 and 374 nm. Thus, fluorescence spectroscopy was simple and easy for studying tyrosine oxidation induced by hydroxyl radical.

  5. Comparison of chemiluminescence methods for analysis of hydrogen peroxide and hydroxyl radicals

    NASA Astrophysics Data System (ADS)

    Pehrman, R.; Amme, M.; Cachoir, C.

    2006-01-01

    Assessment of alpha radiolysis influence on the chemistry of geologically disposed spent fuel demands analytical methods for radiolytic product determination at trace levels. Several chemiluminescence methods for the detection of radiolytic oxidants hydrogen peroxide and hydroxyl radicals are tested. Two of hydrogen peroxide methods use luminol, catalyzed by either μ-peroxidase or hemin, one uses 10-methyl-9-(p-formylphenyl)-acridinium carboxylate trifluoromethanesulfonate and one potassium periodate. All recipes are tested as batch systems in basic conditions. For hydroxyl radical detection luminophores selected are 3-hydroxyphthalic hydrazide and rutin. Both methods are tested as batch systems. The results are compared and the applicability of the methods for near-field dissolution studies is discussed.

  6. The reaction of methionine with hydroxyl radical: reactive intermediates and methanethiol production.

    PubMed

    Spasojević, Ivan; Bogdanović Pristov, Jelena; Vujisić, Ljubodrag; Spasić, Mihajlo

    2012-06-01

    The mechanisms of reaction of methionine with hydroxyl radical are not fully understood. Here, we unequivocally show using electron paramagnetic resonance spin-trapping spectroscopy and GC-FID and GC-MS, the presence of specific carbon-, nitrogen- and sulfur-centered radicals as intermediates of this reaction, as well as the liberation of methanethiol as a gaseous end product. Taking into account the many roles that methionine has in eco- and biosystems, our results may elucidate redox chemistry of this amino acid and processes that methionine is involved in.

  7. Gas-phase photolytic production of hydroxyl radicals in an ultraviolet purifier for air and surfaces.

    PubMed

    Crosley, David R; Araps, Connie J; Doyle-Eisele, Melanie; McDonald, Jacob D

    2017-02-01

    We have measured the concentration of hydroxyl radicals (OH) produced in the gas phase by a commercially available purifier for air and surfaces, using the time rate of decay of n-heptane added to an environmental chamber. The hydroxyl generator, an Odorox® BOSS™ model, produces the OH through 185-nm photolysis of ambient water vapor. The steady-state concentration of OH produced in the 120 m(3) chamber is, with 2σ error bars, (3.25 ± 0.80) × 10(6) cm(-3). The properties of the hydroxyl generator, in particular the output of the ultraviolet lamps and the air throughput, together with an estimation of the water concentration, were used to predict the amount of OH produced by the device, with no fitted parameters. To relate this calculation to a steady-state concentration, we must estimate the OH loss rate within the chamber owing to reaction with the n-heptane and the 7 ppb of background hydrocarbons that are present. The result is a predicted steady-state concentration in excellent agreement with the measured value. This shows we understand well the processes occurring in the gas phase during operation of this hydroxyl radical purifier.

  8. Nighttime formation of peroxy and hydroxyl radicals during the BERLIOZ campaign: Observations and modeling studies

    NASA Astrophysics Data System (ADS)

    Geyer, Andreas; BäChmann, Kurt; Hofzumahaus, Andreas; Holland, Frank; Konrad, Stefan; Klüpfel, Thomas; PäTz, Hans-Werner; Perner, Dieter; Mihelcic, Djuro; SchäFer, Hans-Jürgen; Volz-Thomas, Andreas; Platt, Ulrich

    2003-02-01

    Traditionally, tropospheric radical chemistry is discussed in terms of the daytime photochemically produced hydroxyl radical (OH). Radicals, however, are also important during nighttime: this is especially true for ozone and the nitrate radical (NO3), which both act as key initiators of the degradation of alkenes such as biogenic monoterpenes. These reactions lead to the formation of peroxy radicals (HO2 and RO2) and hydroxyl radicals at night. We present recent observations of nighttime concentrations of NO3, RO2, HO2, and OH by differential optical absorption spectroscopy (DOAS), matrix isolation electron spin resonance (MIESR), laser-induced fluorescence (LIF), and a chemical amplifier (CA) in the framework of the Berliner Ozonexperiment (BERLIOZ) campaign at Pabstthum, Germany, together with modeling studies of nocturnal radical chemistry. Modeled RO2 mixing ratios reached 40 ppt while the measured ROx level went up to 22 ppt at the same time. Modeled and measured HO2 mixing ratios were up to 6 and 4 ppt, respectively. In the case of OH, a nocturnal concentration of (1.85 ± 0.82) × 105 cm-3 was measured during one night. At this time, the model yielded an OH level of (4.1 ± 0.7) × 105 cm-3. This overestimation by the model could point to a missing nocturnal sink of OH. Nitrate radical reactions with terpenes were found responsible for producing 77% of the RO2 radicals, 53% of the HO2, and 36% of the OH radicals during night. Nighttime ozonolysis formed 12% of the RO2, 47% of the HO2, and 64% of the OH radicals. Another 11% of the RO2 radicals were formed by OH-volatile organic compound (VOC) reactions. A positive linear correlation of RO2 and NO3 was observed and could be reproduced in model calculations originating from the loss of both radicals by reaction with NO and the NO3-initiated RO2 production. The contribution of nighttime OH to the atmosphere's oxidation capacity (oxidation rate of VOCs, CO, and CH4) was found negligible (<0.5%).

  9. New technological developments for the remote detection of atmospheric hydroxyl radicals

    NASA Technical Reports Server (NTRS)

    Mcdermid, I. S.; Laudenslager, J. B.; Pacala, T. J.

    1983-01-01

    New developments in the areas of narrowband tunable excimer lasers, high-resolution high-rejection optical filters, and wavelength measurement devices are considered for application to the remote sensing of atmospheric hydroxyl radicals. The conclusion is that an increase in the SNR of 10,000 could readily be gained through the use of these new devices. Also, considerable reductions in size and electrical energy consumption could be realized.

  10. The temperature dependence of the rate constant for the reaction of hydroxyl radicals with nitric acid

    NASA Technical Reports Server (NTRS)

    Kurylo, M. J.; Cornett, K. D.; Murphy, J. L.

    1982-01-01

    The rate constant for the reaction of hydroxyl radicals with nitric acid in the 225-443 K temperature range has been measured by means of the flash photolysis resonance fluorescence technique. Above 300 K, the rate constant levels off in a way that can only be explained by the occurrence of two reaction channels, of which one, operative at low temperatures, proceeds through the formation of an adduct intermediate. The implications of these rate constant values for stratospheric reaction constants is discussed.

  11. Production of hydroxyl radicals by copper-containing metallothionein: roles as prooxidant.

    PubMed

    Suzuki, K T; Rui, M; Ueda, J; Ozawa, T

    1996-11-01

    Production of hydroxyl radicals by copper (Cu)-containing metallothionein (MT) and its relation to zinc (Zn) bound to MT were studied in vitro with reference to the mechanism of the Cu toxicity in the liver of LEC rats. Zn-MT prepared from the liver of Zn-injected rats was reacted with cupric ions at various Cu/Zn ratios, and the concentrations of the two metals bound to MT and in the solution, valence states of Cu in the solution, production of hydroxyl radicals were determined. Cupric ions replaced Zn in MT after being reduced by thiol groups, and MT, worked as an antioxidant. Cupric ions added to MT that did not contain Zn were reduced to cuprous ions by thiol groups in Cu-MT, and the Cu bound to MT was liberated in a form of cuprous ions. Hydroxyl radicals were produced in the presence of hydrogen peroxide in proportion to the amount of cuprous ions liberated from MT. Cu-containing MT was proposed to work as a prooxidant until all thiol groups in MT were oxidized when Zn was not present in MT. The results indicate that MT works as an antioxidant as long as Zn is present in Cu-containing MT, while it works as a prooxidant when Zn is not present by liberating 1.5 M equivalents of cuprous ions relative to cupric ions added, and hydroxyl radicals are produced in the presence of hydrogen peroxide. On the other hand, MT not bound by Cu does not work as a prooxidant throughout.

  12. KINETIC STUDIES OF THE REACTION OF HYDROXYL RADICALS WITH TRICHLOROETHYLENE AND TETRACHLOROETHYLENE. (R826169)

    EPA Science Inventory

    Rate coefficients are reported for the gas-phase reaction of the hydroxyl radical (OH) with C2HCl3 (k1) and C2Cl4 (k2) over an extended temperature range at 740±10 Torr in a He bath gas. These...

  13. Role of hydrogen peroxide and hydroxyl radical in pyrite oxidation by molecular oxygen

    NASA Astrophysics Data System (ADS)

    Schoonen, Martin A. A.; Harrington, Andrea D.; Laffers, Richard; Strongin, Daniel R.

    2010-09-01

    Hydrogen peroxide and hydroxyl radical are readily formed during the oxidation of pyrite with molecular oxygen over a wide range of pH conditions. However, pretreatment of the pyrite surface influences how much of the intermediates are formed and their fate. Acid-washed pyrite produces significant amounts of hydrogen peroxide and hydroxyl radical when suspended in air-saturated water. However, the hydrogen peroxide concentration shows an exponential decrease with time. Suspensions made with partially oxidized pyrite yield significantly lower amounts of hydrogen peroxide product. The presence of Fe(III)-oxide or Fe(III)-hydroxide patches facilitates the conversion of hydrogen peroxide to oxygen and water. Hence, the degree to which a pyrite surface is covered with patches of Fe(III)-oxide or Fe(III)-hydroxide patches is an important control on the concentration of hydrogen peroxide in solution. Hydrogen peroxide appears to be an important intermediate in the four-electron transfer from pyrite to molecular oxygen. Addition of catalase, an enzyme that decomposes hydrogen peroxide to water and molecular oxygen, to a pyrite suspension reduces the oxidation rate by 40%. By contrast, hydroxyl radical does not appear to play a significant role in the oxidation mechanism. It is estimated on the basis of a molecular oxygen and sulfate mass balance that 5-6% of the molecular oxygen is consumed without forming sulfate.

  14. Pulsed electron beam water radiolysis for submicrosecond hydroxyl radical protein footprinting.

    PubMed

    Watson, Caroline; Janik, Ireneusz; Zhuang, Tiandi; Charvátová, Olga; Woods, Robert J; Sharp, Joshua S

    2009-04-01

    Hydroxyl radical footprinting is a valuable technique for studying protein structure, but care must be taken to ensure that the protein does not unfold during the labeling process due to oxidative damage. Footprinting methods based on submicrosecond laser photolysis of peroxide that complete the labeling process faster than the protein can unfold have been recently described; however, the mere presence of large amounts of hydrogen peroxide can also cause uncontrolled oxidation and minor conformational changes. We have developed a novel method for submicrosecond hydroxyl radical protein footprinting using a pulsed electron beam from a 2 MeV Van de Graaff electron accelerator to generate a high concentration of hydroxyl radicals by radiolysis of water. The amount of oxidation can be controlled by buffer composition, pulsewidth, dose, and dissolved nitrous oxide gas in the sample. Our results with ubiquitin and beta-lactoglobulin A demonstrate that one submicrosecond electron beam pulse produces extensive protein surface modifications. Highly reactive residues that are buried within the protein structure are not oxidized, indicating that the protein retains its folded structure during the labeling process. Time-resolved spectroscopy indicates that the major part of protein oxidation is complete in a time scale shorter than that of large scale protein motions.

  15. Discriminative protection against hydroxyl and superoxide anion radicals by quercetin in human leucocytes in vitro.

    PubMed

    Wilms, Lonneke C; Kleinjans, Jos C S; Moonen, Edwin J C; Briedé, Jacob J

    2008-03-01

    Antioxidants play a vital role in the cellular protection against oxidative damage. Quercetin is a well-investigated antioxidant and known to be able to protect against cellular oxidative DNA damage. In this study, we tried to relate the protection by quercetin pre-treatment against oxidative DNA damage in human leucocytes in vitro to the interaction of quercetin in solution with hydroxyl and superoxide anion radicals as measured by electron spin resonance (ESR) spectrometry, using DMPO as a spin trap. Further, scavenging capacity of quercetin-treated leucocytes in vitro was evaluated by ESR spectrometry. Quercetin appears capable of protecting human leucocytes against oxidative DNA damage caused by hydrogen peroxide in a dose-dependent manner. The protection of leucocytes against superoxides is ambiguous. Incubation concentrations of quercetin (1, 10, and 50 microM) reduced levels of superoxide-induced oxidative DNA damage, while at 100 microM the amount of damage was increased. These results are supported by ESR-findings on quercetin in solution, also showing a prooxidant effect at 100 microM. ESR spectroscopy showed rate constant values for the reaction kinetics of quercetin in lowering iron-dependent hydroxyl radical formation and NADH-dependent superoxide anion formation of respectively 3.2 x 10(12)M(-1)s(-1) and 1.1 x 10(4)M(-1)s(-1). This shows that quercetin is a more potent inhibitor of hydroxyl radical formation than a scavenger of superoxide anions.

  16. Pulsed Electron Beam Water Radiolysis for Sub-Microsecond Hydroxyl Radical Protein Footprinting

    PubMed Central

    Watson, Caroline; Janik, Ireneusz; Zhuang, Tiandi; Charvátová, Olga; Woods, Robert J.; Sharp, Joshua S.

    2009-01-01

    Hydroxyl radical footprinting is a valuable technique for studying protein structure, but care must be taken to ensure that the protein does not unfold during the labeling process due to oxidative damage. Footprinting methods based on sub-microsecond laser photolysis of peroxide that complete the labeling process faster than the protein can unfold have been recently described; however, the mere presence of large amounts of hydrogen peroxide can also cause uncontrolled oxidation and minor conformational changes. We have developed a novel method for sub-microsecond hydroxyl radical protein footprinting using a pulsed electron beam from a 2 MeV Van de Graaff electron accelerator to generate a high concentration of hydroxyl radicals by radiolysis of water. The amount of oxidation can be controlled by buffer composition, pulsewidth, dose, and dissolved nitrous oxide gas in the sample. Our results with ubiquitin and β-lactoglobulin A demonstrate that one sub-microsecond electron beam pulse produces extensive protein surface modifications. Highly reactive residues that are buried within the protein structure are not oxidized, indicating that the protein retains its folded structure during the labeling process. Time-resolved spectroscopy indicates that the major part of protein oxidation is complete in a timescale shorter than that of large scale protein motions. PMID:19265387

  17. Modelling On Photogeneration Of Hydroxyl Radical In Surface Waters And Its Reactivity Towards Pharmaceutical Wastes

    SciTech Connect

    Das, Radha; Vione, Davide; Rubertelli, Francesca; Maurino, Valter; Minero, Claudio; Barbati, Stephane; Chiron, Serge

    2010-10-26

    This paper reports a simple model to describe the formation and reactivity of hydroxyl radicals in the whole column of freshwater lakes. It is based on empirical irradiation data and is a function of the water chemical composition (the photochemically significant parameters NPOC, nitrate, nitrite, carbonate and bicarbonate), the lake conformation best expressed as the average depth, and the water absorption spectrum in a simplified Lambert-Beer approach. The purpose is to derive the lifetime of dissolved molecules, due to reaction with OH, on the basis of their second-order rate constants with the hydroxyl radical. The model was applied to two compounds of pharmaceutical wastes ibuprofen and carbamazepine, for which the second-order rate constants for reaction with the hydroxyl radical were measured by means of the competition kinetics with 2-propanol. The measured values of the rate constants are 1.0x10{sup 10} and 1.6x10{sup 10} M{sup -1} s{sup -1} for ibuprofen and carbamazepine, respectively. The model suggests that the lifetime of a given compound can be very variable in different lakes, even more than the lifetime of different compounds in the same lake. It can be concluded that as far as the reaction with OH, is concerned the concepts of photolability and photostability, traditionally attached to definite compounds, are ecosystem-dependent at least as much as they depend on the molecule under consideration.

  18. Modelling On Photogeneration Of Hydroxyl Radical In Surface Waters And Its Reactivity Towards Pharmaceutical Wastes

    NASA Astrophysics Data System (ADS)

    Das, Radha; Vione, Davide; Rubertelli, Francesca; Maurino, Valter; Minero, Claudio; Barbati, Stéphane; Chiron, Serge

    2010-10-01

    This paper reports a simple model to describe the formation and reactivity of hydroxyl radicals in the whole column of freshwater lakes. It is based on empirical irradiation data and is a function of the water chemical composition (the photochemically significant parameters NPOC, nitrate, nitrite, carbonate and bicarbonate), the lake conformation best expressed as the average depth, and the water absorption spectrum in a simplified Lambert-Beer approach. The purpose is to derive the lifetime of dissolved molecules, due to reaction with •OH, on the basis of their second-order rate constants with the hydroxyl radical. The model was applied to two compounds of pharmaceutical wastes ibuprofen and carbamazepine, for which the second-order rate constants for reaction with the hydroxyl radical were measured by means of the competition kinetics with 2-propanol. The measured values of the rate constants are 1.0×1010 and 1.6×1010M-1 s-1 for ibuprofen and carbamazepine, respectively. The model suggests that the lifetime of a given compound can be very variable in different lakes, even more than the lifetime of different compounds in the same lake. It can be concluded that as far as the reaction with •OH, is concerned the concepts of photolability and photostability, traditionally attached to definite compounds, are ecosystem-dependent at least as much as they depend on the molecule under consideration.

  19. The differential effects of superoxide anion, hydrogen peroxide and hydroxyl radical on cardiac mitochondrial oxidative phosphorylation.

    PubMed

    Zini, Roland; Berdeaux, Alain; Morin, Didier

    2007-10-01

    The involvement of reactive oxygen species (ROS) in cardiac ischemia-reperfusion injuries is well-established, but the deleterious effects of hydrogen peroxide (H(2)O(2)), hydroxyl radical (HO*) or superoxide anion (O(2)*(-) ) on mitochondrial function are poorly understood. Here, we report that incubation of rat heart mitochondria with each of these three species resulted in a decline of the ADP-stimulated respiratory rate but not substrate-dependent respiration. These three species reduced oxygen consumption induced by an uncoupler without alteration of the respiratory chain complexes, but did not modify mitochondrial membrane permeability. HO* slightly decreased F1F0-ATPase activity and HO* and O(2)*(-) partially inhibited the activity of adenine nucleotide translocase; H(2)O(2) failed to alter these targets. They inhibited NADH production by acting specifically on aconitase for O(2)*(-) and alpha-ketoglutarate dehydrogenase for H(2)O(2) and HO*. Our results show that O(2)*(-), H(2)O(2) and HO* act on different mitochondrial targets to alter ATP synthesis, mostly through inhibition of NADH production.

  20. Pulse radiolysis of supercritical water II. Reaction of nitrobenzene with hydrated electrons and hydroxyl radicals.

    SciTech Connect

    Marin, T. W.; Cline, J. A.; Bartels, D. M.; Jonah, C. D.; Takahashi, K.; Chemistry; Hakkaido Univ.

    2003-12-26

    The rate constants for the reactions of nitrobenzene with the hydroxyl radical (OH{sup {sm_bullet}}) and hydrated electron ((e{sup -}){sub aq}) in water have been measured from room temperature to 400 {sup o}C using electron pulse radiolysis and transient absorption spectroscopy. The diffusion-limited reaction of nitrobenzene with (e{sup 0}){sub aq} exhibits temperature-insensitive activation energy up to 300 {sup o}C, indicating that the activation energy for electron diffusion remains high over this range. The (e{sup -}){sub aq} reactivity is explained as a long-range electron transfer, and the results are interpreted in terms of extended Marcus theory and Smoluchowski relationships. At 380 {sup o}C, the rate constant has a density dependence similar to that previously reported for other (e{sup -}){sub aq} scavenging reactions. The reaction rate of nitrobenzene with OH{sup {sm_bullet}} is very insensitive to temperature from room temperature up to 300 {sup o}C, in agreement with previous studies. Above 300 {sup o}C, the rate constant increases as the critical temperature is approached and exceeded. Time-resolved electronic absorption spectra of the nitrobenzene radiolysis transients reveal complex kinetics involving multiple absorbing species.

  1. Hydroxyurea induces hydroxyl radical-mediated cell death in Escherichia coli

    PubMed Central

    Davies, Bryan W.; Kohanski, Michael A.; Simmons, Lyle A.; Winkler, Jonathan A.; Collins, James J.; Walker, Graham C.

    2010-01-01

    SUMMARY Hydroxyurea (HU) specifically inhibits class I ribonucleotide reductase (RNR), depleting dNTP pools and leading to replication fork arrest. While HU inhibition of RNR has been recognized for decades, the mechanism by which it leads to cell death remains unknown. To investigate the mechanism of HU-induced cell death we used a systems-level approach to determine the genomic and physiological responses of E. coli to HU treatment. Our results suggest a model by which HU treatment rapidly induces a set of protective responses to manage genomic instability in the majority of the cell population. Continued HU stress activates iron uptake as well as the toxins MazF and RelE whose activity causes the synthesis of incompletely translated proteins and stimulation of the envelope stress response system. These effects alter the properties of one of the cell’s two terminal cytochrome oxidases in the electron transport chain, causing an increase in the production of superoxide. The increased superoxide production from the respiratory chain together with the increased iron uptake fuels the formation of hydroxyl radicals that contribute to HU-induced cell death. This work significantly expands our understanding of HU-mediated cell death and more broadly suggests a pathway whereby replication fork arrest leads to cell death. PMID:20005847

  2. Rates of hydroxyl radical production from transition metals and quinones in a surrogate lung fluid

    PubMed Central

    Charrier, Jessica G.; Anastasio, Cort

    2016-01-01

    Hydroxyl radical (.OH) is the most reactive, and perhaps most detrimental to health, of the reactive oxygen species. .OH production in lungs following inhalation of particulate matter (PM) can result from redox-active chemicals, including iron and copper, but the relative importance of these species is unknown. This work investigates .OH production from iron, copper, and quinones, both individually and in mixtures at atmospherically relevant concentrations. Iron, copper and three of the four quinones (1,2-naphthoquinone, phenanthrenequinone and 1,4-naphthoquinone) produce .OH. Mixtures of copper or quinones with iron synergistically produce .OH at a rate 20 - 130% higher than the sum of the rates of the individual redox-active species. We developed a regression equation from 20 mixtures to predict the rate of .OH production from the particle composition. For typical PM compositions, iron and copper account for most .OH production, while quinones are a minor source, although they can contribute if present at very high concentrations. This work shows that Cu contributes significantly to .OH production in ambient PM; other work has shown that Cu appears to be the primary driver of HOOH production and dithiothreitol (DTT) loss in ambient PM extracts. Taken together, these results indicate that copper appears to be the most important individual contributor to direct oxidant production from inhaled PM. PMID:26153923

  3. Assessing the contribution of free hydroxyl radical in organic matter-sensitized photohydroxylation reactions.

    PubMed

    Page, Sarah E; Arnold, William A; McNeill, Kristopher

    2011-04-01

    Photochemical formation of reactive oxygen species from dissolved organic matter (DOM) is incompletely understood, especially in the case of hydroxyl radical (•OH) production. Many studies have used various probes to detect photochemically produced •OH from DOM, but the fundamental reactions of these probes are not necessarily specific for free •OH and may also detect lower-energy hydroxylation agents. In this study, two tests were applied that have previously been used as a diagnostic for the presence of free •OH: methane quenching of •OH and hydroxybenzoic acid (hBZA) product yields. Upon application of these two tests to a set of five DOM isolates, it was found that methane quenching and the hBZA ratio results were not necessarily consistent. Overall, the results provide compelling evidence that all isolates studied photochemically produce free •OH. The hydroxylating acitivity of Elliot Soil Humic Acid and Pony Lake Fulvic Acid, however, also had a significant contribution from a photochemically generated hydroxylating agent that is lower in energy than free •OH. Catalase quenching experiments were conducted to assess whether hydrogen peroxide was the immediate precursor to hydroxyl in these systems. In all cases, catalase addition slowed photohydroxylation of terephthalate, but the contribution of hydrogen peroxide photolysis was determined to be less than 50%.

  4. Physicochemical properties of iron oxide nanoparticles that contribute to cellular ROS-dependent signaling and acellular production of hydroxyl radical.

    PubMed

    Vogel, Christoph F A; Charrier, Jessica G; Wu, Dalei; McFall, Alexander S; Li, Wen; Abid, Aamir; Kennedy, Ian M; Anastasio, Cort

    2016-01-01

    While nanoparticles (NPs) are increasingly used in a variety of consumer products and medical applications, some of these materials have potential health concerns. Macrophages are the primary responders to particles that initiate oxidative stress and inflammatory reactions. Here, we utilized six flame-synthesized, engineered iron oxide NPs with various physicochemical properties (e.g. Fe oxidation state and crystal size) to study their interactions with RAW 264.7 macrophages, their iron solubilities, and their abilities to produce hydroxyl radical in an acellular assay. Both iron solubility and hydroxyl radical production varied between NPs depending on crystalline diameter and surface area of the particles, but not on iron oxidation state. Macrophage treatment with the iron oxide NPs showed a dose-dependent increase of heme oxygenase 1 (HO-1) and NAD(P)H:quinone oxidoreductase (NQO-1). The nuclear factor (NF)-erythroid-derived 2 (E2)-related factor 2 (Nrf2) modulates the transcriptional activity of antioxidant response element (ARE)-driven genes, such as HO-1 and NQO-1. Here, we show that the iron oxide NPs activate Nrf2, leading to its increased nuclear accumulation and enhanced Nrf2 DNA-binding activity in NP-treated RAW 264.7 macrophages. Iron solubility and acellular hydroxyl radical generation depend on the physical properties of the NPs, especially crystalline diameter; however, these properties are weakly linked to the activation of cellular signaling of Nrf2 and the expression of oxidative stress markers. Overall, our work shows for the first time that iron oxide nanoparticles induce cellular marker genes of oxidative stress and that this effect is transcriptionally mediated through the Nrf2-ARE signaling pathway in macrophages.

  5. Release of free amino acids upon oxidation of peptides and proteins by hydroxyl radicals.

    PubMed

    Liu, Fobang; Lai, Senchao; Tong, Haijie; Lakey, Pascale S J; Shiraiwa, Manabu; Weller, Michael G; Pöschl, Ulrich; Kampf, Christopher J

    2017-03-01

    Hydroxyl radical-induced oxidation of proteins and peptides can lead to the cleavage of the peptide, leading to a release of fragments. Here, we used high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) and pre-column online ortho-phthalaldehyde (OPA) derivatization-based amino acid analysis by HPLC with diode array detection and fluorescence detection to identify and quantify free amino acids released upon oxidation of proteins and peptides by hydroxyl radicals. Bovine serum albumin (BSA), ovalbumin (OVA) as model proteins, and synthetic tripeptides (comprised of varying compositions of the amino acids Gly, Ala, Ser, and Met) were used for reactions with hydroxyl radicals, which were generated by the Fenton reaction of iron ions and hydrogen peroxide. The molar yields of free glycine, aspartic acid, asparagine, and alanine per peptide or protein varied between 4 and 55%. For protein oxidation reactions, the molar yields of Gly (∼32-55% for BSA, ∼10-21% for OVA) were substantially higher than those for the other identified amino acids (∼5-12% for BSA, ∼4-6% for OVA). Upon oxidation of tripeptides with Gly in C-terminal, mid-chain, or N-terminal positions, Gly was preferentially released when it was located at the C-terminal site. Overall, we observe evidence for a site-selective formation of free amino acids in the OH radical-induced oxidation of peptides and proteins, which may be due to a reaction pathway involving nitrogen-centered radicals.

  6. Dual contradictory roles of cAMP signaling pathways in hydroxyl radical production in the rat striatum.

    PubMed

    Hara, Shuichi; Kobayashi, Masamune; Kuriiwa, Fumi; Mukai, Toshiji; Mizukami, Hajime

    2012-03-15

    Studies have suggested that cAMP signaling pathways may be associated with the production of reactive oxygen species. In this study, we examined how modifications in cAMP signaling affected the production of hydroxyl radicals in rat striatum using microdialysis to measure extracellular 2,3-dihydroxybenzoic acid (2,3-DHBA), which is a hydroxyl radical adduct of salicylate. Up to 50 nmol of the cell-permeative cAMP mimetic 8-bromo-cAMP (8-Br-cAMP) increased 2,3-DHBA in a dose-dependent manner (there was no additional increase in 2,3-DHBA at 100 nmol). Another cAMP mimetic, dibutyryl cAMP (db-cAMP), caused a nonsignificant increase in 2,3-DHBA at 50 nmol and a significant decrease at 100 nmol. Up to 20 nmol of forskolin, which is a direct activator of adenylyl cyclase, increased 2,3-DHBA, similar to the effect of 8-Br-cAMP; however, forskolin resulted in a much greater increase in 2,3-DHBA. A potent inhibitor of protein kinase A (PKA), H89 (500 μM), potentiated the 8-Br-cAMP- and forskolin-induced increases in 2,3-DHBA and antagonized the inhibitory effect of 100 nmol of db-cAMP. Interestingly, the administration of 100 nmol of 8-bromo-cGMP alone or in combination with H89 had no significant effect on 2,3-DHBA levels. Doses of 100 nmol of a preferential PKA activator (6-phenyl-cAMP) or a preferential PKA inhibitor (8-bromoadenosine-3',5'-cyclic monophosphorothionate, Rp-isomer; Rp-8-Br-cAMPS), which also inhibits the cAMP-mediated activation of Epac (the exchange protein directly activated by cAMP), suppressed or enhanced, respectively, the formation of 2,3-DHBA. Up to 100 nmol of 8-(4-chlorophenylthio)-2'-O-methyladenosine-cAMP, which is a selective activator of Epac, dose-dependently stimulated the formation of 2,3-DHBA. These findings suggest that cAMP signaling plays contradictory roles (stimulation and inhibition) in the production of hydroxyl radicals in rat striatum by differential actions of Epac and PKA. These roles might contribute to the production of

  7. Quantitative characterization of hydroxyl radical generation in a goethite-catalyzed Fenton-like reaction.

    PubMed

    Lin, Zhi-Rong; Zhao, Ling; Dong, Yuan-Hua

    2015-12-01

    In order to find out the truth of influence of solution chemistry on the oxidation efficiency of a goethite-catalyzed Fenton-like reaction, the amount of hydroxyl radicals (OH) was quantified by using coumarin as its trapping agent to produce the only fluorescent derivative 7-hydroxycoumarin (7-HC), because OH was the reactive species responsible for the oxidation activity of Fenton reactions. The concentration of OH achieved maximum at solution pH of 3 and decreased with an increase of solution pH value. However, considerable amount of OH can also generate at near neutral pH (i.e. pH 6 and 7). The concentration of OH was increased both with increasing of goethite and H2O2 dosages, but H2O2 could compete with coumarin to scavenge OH to reduce the formation of 7-HC when the concentration of H2O2 was too high. Anions inhibited OH generation followed an order of H2PO4(-)>SO4(2-)>Cl(-)>NO3(-)>ClO4(-). Higher concentrations of Cl(-) and SO4(2-) resulted in greater inhibition of OH generation. Results of this study demonstrated that the influence of solution chemistry on the oxidation efficiency of the goethite-catalyzed Fenton-like reaction was greatly attributed to the effect of solution chemistry on the amount of OH formed in the process of reaction.

  8. Reactivity of hydroxyl radicals with neonicotinoid insecticides: mechanism and changes in toxicity.

    PubMed

    Dell'arciprete, María L; Santos-Juanes, Lucas; Sanz, Antonio Arques; Vicente, Rafael; Amat, Ana M; Furlong, Jorge P; Mártire, Daniel O; Gonzalez, Mónica C

    2009-07-01

    The reactivity of hydroxyl radicals (HO ) towards three neonicotonoid insecticides, namely imidacloprid, thiacloprid and acetamiprid was investigated. These radicals were generated by photolysis of H(2)O(2) solutions. Flash photolysis experiments were used to determine the rate constants of 5.5 x 10(10) M(-1)s(-1), 6 x 10(10) M(-1)s(-1), and 7.5 x 10(10) M(-1)s(-1), for the reactions of HO with acetamiprid, imidacloprid, and thiacloprid, respectively. Continuous irradiation experiments in the absence and presence of H(2)O(2) allowed the identification and toxicity evaluation of the primary photo- and oxidation products of the insecticides. In all cases, the less toxic 6-chloronicotinic acid was found to be the major product at higher degrees of oxidation. The results reported here indicate that the half life of the insecticides due to their reaction with HO radicals in natural aquatic reservoirs may vary between 5 h and 19 days, and therefore the hydroxyl radical-mediated oxidation may be a significant abiotic elimination route. However, elimination of the insecticide under such conditions might not improve the quality of the contaminated water, as the primary products of degradation still show considerable toxicity to Vibrio fischeri assays.

  9. Degradation pathways of lamotrigine under advanced treatment by direct UV photolysis, hydroxyl radicals, and ozone.

    PubMed

    Keen, Olya S; Ferrer, Imma; Michael Thurman, E; Linden, Karl G

    2014-12-01

    Lamotrigine is recently recognized as a persistent pharmaceutical in the water environment and wastewater effluents. Its degradation was studied under UV and ozone advanced oxidation treatments with reaction kinetics of lamotrigine with ozone (≈4 M(-1)s(-1)), hydroxyl radical [(2.1 ± 0.3) × 10(9)M(-1)s(-1)] and by UV photolysis with low and medium pressure mercury vapor lamps [quantum yields ≈0 and (2.7 ± 0.4)× 10(-4) respectively] determined. All constants were measured at pH 6 and at temperature ≈20°C. The results indicate that lamotrigine is slow to respond to direct photolysis or oxidation by ozone and no attenuation of the contaminant is expected in UV or ozone disinfection applications. The compound reacts rapidly with hydroxyl radicals indicating that advanced oxidation processes would be effective for its treatment. Degradation products were identified under each treatment process using accurate mass time-of-flight spectrometry and pathways of decay were proposed. The main transformation pathways in each process were: dechlorination of the benzene ring during direct photolysis; hydroxyl group addition to the benzene ring during the reaction with hydroxyl radicals; and triazine ring opening after reaction with ozone. Different products that form in each process may be to a varying degree less environmentally stable than the parent lamotrigine. In addition, a novel method of ozone quenching without addition of salts is presented. The new quenching method would allow subsequent mass spectrometry analysis without a solid phase extraction clean-up step. The method involves raising the pH of the sample to approximately 10 for a few seconds and lowering it back and is therefore limited to applications for which temporary pH change is not expected to affect the outcome of the analysis.

  10. Hydroxyl Radical (OH•) Reaction with Guanine in an Aqueous Environment: A DFT Study

    PubMed Central

    Kumar, Anil; Pottiboyina, Venkata; Sevilla, Michael D.

    2011-01-01

    The reaction of hydroxyl radical (OH•) with DNA accounts for about half of radiation-induced DNA damage in living systems. Previous literature reports point out that the reaction of OH• with DNA proceeds mainly through the addition of OH• to the C=C bond of the DNA bases. However, recently it has been reported that the principal reaction of OH• with dGuo (deoxyguanosine) is the direct hydrogen atom abstraction from its exocyclic amine group rather than addition of OH• to the C=C bond. In the present work, these two reaction pathways of OH• attack on guanine (G) in the presence of water molecules (aqueous environment) are investigated using the density functional theory (DFT) B3LYP method with 6-31G* and 6-31++G** basis sets. The calculations show that the initial addition of the OH• at C4=C5 double bond of guanine is barrier free and the adduct radical (G-OH•) has only a small activation barrier of ca. 1 – 6 kcal/mol leading to the formation of a metastable ion-pair intermediate (G•+---OH−). The formation of ion-pair is a result of the highly oxidizing nature of the OH• in aqueous media. The resulting ion-pair (G•+---OH−) deprotonates to form H2O and neutral G radicals favoring G(N1-H)• with an activation barrier of ca. 5 kcal/mol. The overall process from the G(C4)-OH• (adduct) to G(N1-H)• and water is found to be exothermic in nature by more than 13 kcal/mol. (G-OH•), (G•+---OH−), and G(N1-H)• were further characterized by the CAM-B3LYP calculations of their UV-visible spectra and good agreement between theory and experiment is achieved. Our calculations for the direct hydrogen abstraction pathway from N1 and N2 sites of guanine by the OH• show that this is also a competitive route to produce G(N2-H)•, G(N1-H)• and H2O. PMID:22050033

  11. Modeling of the long-term tropospheric trends of hydroxyl radical for the Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Kiselev, Andrey A.; Karol, Igor L.

    The MGO 2D (altitude-longitude) channel photochemical transport model has been applied to elucidate the spatial and temporal behavior of the hydroxyl radical in the troposphere of the northern temperate belt for the pre-industrial (1850) period and the last few decades (1960 and 1995). The relation between the tropospheric OH content and the carbon monoxide, methane, nitrogen oxides emissions during 1850-1995 is studied. The distribution of the carbon monoxide concentration is calculated and validated using the observational data collected in the different locations because of the geographical non-homogeneity of its emissions. The response of the hydroxyl radical concentrations to the non-homogeneity of the CO and other atmospheric species distribution is estimated. The carbon monoxide and methane contributions to the hydroxyl photochemical sink are also evaluated. Because the changes of OH in the troposphere alternate the intensity of methane and carbon monoxide oxidation, the CO, CH 4 and OH lifetime evolution due to the increase of anthropogenic pollution intensity is analyzed and discussed.

  12. Rapid Killing of Acinetobacter baumannii by Polymyxins Is Mediated by a Hydroxyl Radical Death Pathway

    PubMed Central

    Sampson, Timothy R.; Liu, Xiang; Schroeder, Max R.; Kraft, Colleen S.; Burd, Eileen M.

    2012-01-01

    Acinetobacter baumannii is an opportunistic pathogen that is a cause of clinically significant nosocomial infections. Increasingly, clinical isolates of A. baumannii are extensively resistant to numerous antibiotics, and the use of polymyxin antibiotics against these infections is often the final treatment option. Historically, the polymyxins have been thought to kill bacteria through membrane lysis. Here, we present an alternative mechanism based on data demonstrating that polymyxins induce rapid cell death through hydroxyl radical production. Supporting this notion, we found that inhibition of radical production delays the ability of polymyxins to kill A. baumannii. Notably, we demonstrate that this mechanism of killing occurs in multidrug-resistant clinical isolates of A. baumannii and that this response is not induced in a polymyxin-resistant isolate. This study is the first to demonstrate that polymyxins induce rapid killing of A. baumannii and other Gram-negatives through hydroxyl radical production. This significantly augments our understanding of the mechanism of polymyxin action, which is critical knowledge toward the development of adjunctive therapies, particularly given the increasing necessity for treatment with these antibiotics in the clinical setting. PMID:22908157

  13. Rapid killing of Acinetobacter baumannii by polymyxins is mediated by a hydroxyl radical death pathway.

    PubMed

    Sampson, Timothy R; Liu, Xiang; Schroeder, Max R; Kraft, Colleen S; Burd, Eileen M; Weiss, David S

    2012-11-01

    Acinetobacter baumannii is an opportunistic pathogen that is a cause of clinically significant nosocomial infections. Increasingly, clinical isolates of A. baumannii are extensively resistant to numerous antibiotics, and the use of polymyxin antibiotics against these infections is often the final treatment option. Historically, the polymyxins have been thought to kill bacteria through membrane lysis. Here, we present an alternative mechanism based on data demonstrating that polymyxins induce rapid cell death through hydroxyl radical production. Supporting this notion, we found that inhibition of radical production delays the ability of polymyxins to kill A. baumannii. Notably, we demonstrate that this mechanism of killing occurs in multidrug-resistant clinical isolates of A. baumannii and that this response is not induced in a polymyxin-resistant isolate. This study is the first to demonstrate that polymyxins induce rapid killing of A. baumannii and other Gram-negatives through hydroxyl radical production. This significantly augments our understanding of the mechanism of polymyxin action, which is critical knowledge toward the development of adjunctive therapies, particularly given the increasing necessity for treatment with these antibiotics in the clinical setting.

  14. Apparent hydroxyl radical production by peroxynitrite: implications for endothelial injury from nitric oxide and superoxide.

    PubMed Central

    Beckman, J S; Beckman, T W; Chen, J; Marshall, P A; Freeman, B A

    1990-01-01

    Superoxide dismutase reduces injury in many disease processes, implicating superoxide anion radical (O2-.) as a toxic species in vivo. A critical target of superoxide may be nitric oxide (NO.) produced by endothelium, macrophages, neutrophils, and brain synaptosomes. Superoxide and NO. are known to rapidly react to form the stable peroxynitrite anion (ONOO-). We have shown that peroxynitrite has a pKa of 7.49 +/- 0.06 at 37 degrees C and rapidly decomposes once protonated with a half-life of 1.9 sec at pH 7.4. Peroxynitrite decomposition generates a strong oxidant with reactivity similar to hydroxyl radical, as assessed by the oxidation of deoxyribose or dimethyl sulfoxide. Product yields indicative of hydroxyl radical were 5.1 +/- 0.1% and 24.3 +/- 1.0%, respectively, of added peroxynitrite. Product formation was not affected by the metal chelator diethyltriaminepentaacetic acid, suggesting that iron was not required to catalyze oxidation. In contrast, desferrioxamine was a potent, competitive inhibitor of peroxynitrite-initiated oxidation because of a direct reaction between desferrioxamine and peroxynitrite rather than by iron chelation. We propose that superoxide dismutase may protect vascular tissue stimulated to produce superoxide and NO. under pathological conditions by preventing the formation of peroxynitrite. PMID:2154753

  15. Metal-induced hydroxyl radical generation by Cu(+)-metallothioneins from LEC rat liver.

    PubMed

    Nakamura, M; Nakayama, K; Shishido, N; Yumino, K; Ohyama, T

    1997-02-24

    Reactions of LEC (Long-Evans rats with a cinnamonlike coat color) rat liver Cu(I)-metallothioneins (MTs) with HgCl2 or K3Fe(CN)6 were investigated by ESR spectroscopy and generation of hydroxyl radicals was demonstrated using the ESR spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO). When Cu(I)-MTs were incubated with more than one equivalent mole HgCl2 or K3Fe(CN)6 to Cu+ bound to MTs, strong signals due to Cu2+ appeared. ESR spectra, which were a combination of the DMPO-OH adduct signal and a six-line signal, were observed in the reaction of Cu(I)-MTs with HgCl2, whereas no oxygen radical signal was seen with K3Fe(CN)6. The DMPO-OH signal intensity was greater in the presence of SOD while the signal disappeared in the presence of catalase. The results suggest that addition of HgCl2 causes the liberation of cuprous ions from MTs followed by a reaction with oxygen, leading to hydroxyl radical formation through a Fenton-type Haber-Weiss reaction.

  16. Enhanced recognition of hydroxyl radical modified plasmid DNA by circulating cancer antibodies.

    PubMed

    Khan, F; Ali, A; Ali, R

    2005-06-01

    Reactive oxygen species have been implicated in various human diseases which are also responsible for the elimination of invading pathogens. In disease state and inflammatory responses, the excess of these radicals damage cellular macromolecules. DNA is susceptible to attacks by OH-induced damage. Oxidative DNA damage is an important factor in mutagenesis and carcinogenesis. In the present study, purified plasmid Bluescript DNA was modified by hydroxyl radical. Modifications incurred in DNA were characterized by physico-chemical techniques. Sera from patients of cancer were studied for their binding to native and hydroxyl radical modified plasmid DNA. Direct binding ELISA and competition binding results indicated that autoantibodies in cancer showed higher recognition to ROS-plasmid DNA as compared to the native form. Retarded mobility of the immune complex formation between IgG isolated from cancer sera using native and ROS-plasmid DNA as antigens reiterated preferential recognition of modified plasmid DNA by cancer autoantibodies. Therefore, it can be concluded that circulating autoantibodies in cancer sera bind preferentially to ROS-plasmid DNA as compared to native polymer. The data presented in the present communication suggest a role of ROS in the etiology of cancer.

  17. Free Radical Scavenging Activity of Leaves of Alocasia indica (Linn).

    PubMed

    Mulla, W A; Salunkhe, V R; Kuchekar, S B; Qureshi, M N

    2009-05-01

    The free radical scavenging potential of the plant Alocasia indica(Linn.) was studied by using different antioxidant models of screening like scavenging of 1,1-diphenyl-2-picryl hydrazyl radical, nitric oxide radical, superoxide anion radical, hydroxyl radical, iron chelating activity, total antioxidant capacity, non-enzymatic glycosylation of haemoglobin, rapid screening for antioxidant compounds by thin layer chromatography. The hydroalcoholic extract at 1000 mug/ml showed maximum scavenging of superoxide radical (87.17) by riboflavin-NBT-system, followed by scavenging of stable radical 1,1-diphenyl-2-picryl hydrazyl radical (83.48%), nitric oxide radical (74.09%) hydroxyl radical (60.96%) at the same concentration. However the extract showed only moderate activity by iron chelation (68.26%). That could be due to higher phenolic content in the extract. This finding suggests that hydro alcoholic extract of A. indica possess potent in vitro antioxidant activity as compared to the standard ascorbic acid. The results justify the therapeutic applications of the plant in the indigenous system of medicine, augmenting its therapeutic value.

  18. The impact of the hydroxyl radical photochemical sources on the rivastigmine drug transformation in mimic and natural waters.

    PubMed

    Passananti, Monica; Temussi, Fabio; Iesce, Maria Rosaria; Mailhot, Gilles; Brigante, Marcello

    2013-09-15

    In this paper we investigated the degradation of the rivastigmine drug induced by hydroxyl radical in synthetic and natural waters focusing on both reactivity and photoproducts identification. The hydroxyl radical formation rate was quantified by using terephthalic acid as trapping molecule and it was related with the rivastigmine degradation rate. The second order rate constant between hydroxyl radical and rivastigmine was estimated to be ≈ 5.8 × 10(9) M(-1) s(-1). Irradiation of rivastigmine in three natural waters (rain, lake and river) and comparison with degradation rates observed in synthetic solutions using nitrite, nitrate and hydrogen peroxide suggest that, in addition to hydroxyl radical, also nitroderived radicals (NO/NO2) are responsible for the pollutant degradation in natural media. In fact, the evaluated degradation rates in three natural waters are greatly higher than those estimated considering only the reactivity with photogenerated hydroxyl radical. Using nitrites and nitrates as photochemical OH source, the rivastigmine degradation cannot be described considering only the hydroxyl radical reactivity suggesting that NO and NO2 radicals could play a key role during indirect degradation. Moreover main degradation products have been identified by means of HPLC-MS. Hydroxylation of the aromatic ring as well as carbamate and amino chain oxidation were suggested as main reaction mechanisms, but also nitroderived compounds were characterized. Finally polychromatic irradiations of three rivastigmine doped natural waters (rain, river and lake) underlined the role of the indirect degradation that needs to be considered when direct degradation of selected pollutants is negligible under environmental-like conditions.

  19. Free Radical Chemistry of Disinfection Byproducts 1: Kinetics of Hydrated Electron and Hydroxyl Radical Reactions with Halonitromethanes in Water

    SciTech Connect

    B. J. Mincher; R. V. Fox; S. P. Mezyk; T. Helgeson; S. K. Cole; W. J. Cooper; P. R. Gardinali

    2006-01-01

    Halonitromethanes are disinfection-byproducts formed during ozonation and chlorine/chloramine treatment of waters that contain bromide ion and natural organic matter. In this study, the chemical kinetics of the free-radical-induced degradations of a series of halonitromethanes were determined. Absolute rate constants for hydroxyl radical, OH, and hydrated electron, eaq-, reaction with both chlorinated and brominated halonitromethanes were measured using the techniques of electron pulse radiolysis and transient absorption spectroscopy. The bimolecular rate constants obtained, k (M-1 s-1), for eaq-/OH, respectively, were the following: chloronitromethane (3.01 ± 0.40) × 1010/(1.94 ± 0.32) × 108; dichloronitromethane (3.21 ± 0.17) × 1010/(5.12 ± 0.77) × 108; bromonitromethane (3.13 ± 0.06) × 1010/(8.36 ± 0.57) × 107; dibromonitromethane (3.07 ± 0.40) × 1010/(4.75 ± 0.98) × 108; tribromonitromethane (2.29 ± 0.39) × 1010/(3.25 ± 0.67) × 108; bromochloronitromethane (2.93 ± 0.47) × 1010/(4.2 ± 1.1) × 108; bromodichloronitromethane (2.68 ± 0.13) × 1010/(1.02 ± 0.15) × 108; and dibromochloronitromethane (2.95 ± 0.43) × 1010 / (1.80 ± 0.31) × 108 at room temperature and pH ~7. Comparison data were also obtained for hydroxyl radical reaction with bromoform (1.50 ± 0.05) × 108, bromodichloromethane (7.11 ± 0.26) × 107, and chlorodibromomethane (8.31 ± 0.25) × 107 M-1 s-1, respectively. These rate constants are compared to recently obtained data for trichloronitromethane and bromonitromethane, as well as to other established literature data for analogous compounds.

  20. Hydroxyl radical-induced degradation of fenuron in pulse and gamma radiolysis: kinetics and product analysis.

    PubMed

    Kovács, Krisztina; Mile, Viktoria; Csay, Tamás; Takács, Erzsébet; Wojnárovits, László

    2014-11-01

    Radiolytic reactions of phenylureas were studied in detail with fenuron model compound in dilute aqueous solutions using pulse radiolysis for detection of the intermediates, gamma radiolysis with UV-Vis and HPLC-MS techniques for analysis of the final products. The kinetics of oxidation was followed by COD, TOC and toxicity measurements. During radiolysis of aerated solutions hydroxyl radical ((•)OH), eaq (-), H(•) and O2 (•-)/HO2 (•) reactive intermediates are produced, the degradation of solute takes place practically entirely through (•)OH reactions. Therefore, the product distribution is similar to the distributions reported in other advanced oxidation processes with (•)OH as main reactant. (•)OH mainly reacts with the aromatic ring, forming cyclohexadienyl radical as an intermediate. This radical in pulse radiolysis has a wide absorption band in the 310-390 nm wavelength range with a maximum at 350 nm. Cyclohexadienyl radical reacts with dissolved O2 with a rate coefficient of ∼ 4 × 10(8) mol(-1) dm(3) s(-1) forming peroxy radical. The latter may eliminate HO2 (•) giving phenols or undergoes fragmentation. The one-electron oxidant (•)OH on average induces more than two-electron oxidations. The toxicity first increases with absorbed dose, then decreases. This increase is partly due to phenols formed during the first degradation period.

  1. Levofloxacin oxidation by ozone and hydroxyl radicals: kinetic study, transformation products and toxicity.

    PubMed

    Hamdi El Najjar, Nasma; Touffet, Arnaud; Deborde, Marie; Journel, Romain; Leitner, Nathalie Karpel Vel

    2013-10-01

    This work was carried out to investigate the fate of the antibiotic levofloxacin upon oxidation with ozone and hydroxyl radicals. A kinetic study was conducted at 20 °C for each oxidant. Ozonation experiments were performed using a competitive kinetic method with carbamazepin as competitor. Significant levofloxacin removal was observed during ozonation and a rate constant value of 6.0×10(4) M(-1) s(-1) was obtained at pH 7.2. An H2O2/UV system was used for the formation of hydroxyl radicals HO. The rate constant of HO was determined in the presence of a high H2O2 concentration. The kinetic expressions yielded a [Formula: see text] value of 4.5×10(9) M(-1) s(-1) at pH 6.0 and 5.2×10(9) M(-1) s(-1) at pH 7.2. These results were used to develop a model to predict the efficacy of the ozonation process and pharmaceutical removal was estimated under different ozonation conditions (i.e. oxidant concentrations and contact times). The results showed that levofloxacin was completely degraded by molecular ozone during ozonation of water and that hydroxyl radicals had no effect in real waters conditions. Moreover, LC/MS/MS and toxicity assays using Lumistox test were performed to identify ozonation transformation products. Under these conditions, four transformation products were observed and their chemical structures were proposed. The results showed an increase in toxicity during ozonation, even after degradation of all of the observed transformation products. The formation of other transformation products not identified under our experimental conditions could be responsible for the observed toxicity. These products might be ozone-resistant and more toxic to Vibrio fisheri than levofloxacin.

  2. Silicon ameliorates manganese toxicity in cucumber by decreasing hydroxyl radical accumulation in the leaf apoplast.

    PubMed

    Dragišić Maksimović, Jelena; Mojović, Miloš; Maksimović, Vuk; Römheld, Volker; Nikolic, Miroslav

    2012-04-01

    This work was focused on the role of silicon (Si) in amelioration of manganese (Mn) toxicity caused by elevated production of hydroxyl radicals (·OH) in the leaf apoplast of cucumber (Cucumis sativus L.). The plants were grown in nutrient solutions with adequate (0.5 μM) or excessive (100 μM) Mn concentrations with or without Si being supplied. The symptoms of Mn toxicity were absent in the leaves of Si-treated plants subjected to excess Mn, although the leaf Mn concentration remained extremely high. The apoplastic concentration of free Mn(2+) and H(2)O(2) of high Mn-treated plants was significantly decreased by Si treatment. Si supply suppressed the Mn-induced increased abundance of peroxidase (POD) isoforms in the leaf apoplastic fluid, and led to a rapid suppression of guaiacol-POD activity under excess Mn. The spin-trapping reagent 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide was used to detect ·OH by electron paramagnetic resonance spectroscopy. Although supplying Si markedly decreased the accumulation of ·OH in the leaf apoplast with excess Mn, adding monosilicic acid to the Mn(2+)/H(2)O(2) reaction mixture did not directly affect the Fenton reaction in vitro. The results indicate that Si contributes indirectly to a decrease in ·OH in the leaf apoplast by decreasing the free apoplastic Mn(2+), thus regulating the Fenton reaction. A direct inhibitory effect of Si on guaiacol-POD activity (demonstrated in vitro) may also contribute to decreasing the POD-mediated generation of ·OH.

  3. Hydroxyl Radical-Mediated Novel Modification of Peptides: N-Terminal Cyclization through the Formation of α-Ketoamide.

    PubMed

    Lee, Seon Hwa; Kyung, Hyunsook; Yokota, Ryo; Goto, Takaaki; Oe, Tomoyuki

    2015-01-20

    The hydroxyl radical-mediated oxidation of peptides and proteins constitutes a large group of post-translational modifications that can result in structural and functional changes. These oxidations can lead to hydroxylation, sulfoxidation, or carbonylation of certain amino acid residues and cleavage of peptide bonds. In addition, hydroxyl radicals can convert the N-terminus of peptides to an α-ketoamide via abstraction of the N-terminal α-hydrogen and hydrolysis of the ketimine intermediate. In the present study, we identified N-terminal cyclization as a novel modification mediated by a hydroxyl radical. The reaction of angiotensin (Ang) II (DRVYIHPF) and the hydroxyl radical generated by the Cu(II)/ascorbic acid (AA) system or UV/hydrogen peroxide system produced N-terminal cyclized-Ang II (Ang C) and pyruvamide-Ang II (Ang P, CH3COCONH-RVYIHPF). The structure of Ang C was confirmed by mass spectrometry and comparison to an authentic standard. The subsequent incubation of isolated Ang P in the presence of Cu(II)/AA revealed that Ang P was the direct precursor of Ang C. The proposed mechanism involves the formation of a nitrogen-centered (aminyl) radical, which cyclizes to form a five-membered ring containing the alkoxy radical. The subsequent β-scission reaction of the alkoxyl radical results in the cleavage of the terminal CH3CO group. The initial aminyl radical can be stabilized by chelation to the Cu(II) ions. The affinity of Ang C toward the Ang II type 1 receptor was significantly lower than that of Ang II or Ang P. Ang C was not further metabolized by aminopeptidase A, which converts Ang II to Ang III. Hydroxyl radical-mediated N-terminal cyclization was also observed in other Ang peptides containing N-terminal alanine, arginine, valine, and amyloid β 1-11 (DAEFRHDSGYE).

  4. Measurement of Hydroxyl Radicals in Plasma Pencil by Laser Induced Fluorescence

    DTIC Science & Technology

    2013-07-01

    1. Introduction The hydroxyl (OH) radical is frequently gener- ated in electric discharges ignited in gases contain- ing water vapour or organic...International Conference on Phenomena in Ionized Gases (31st) (ICPIG) Held in Granada, Spain on 14-19 July 2013, The original document contains color images. 14...A.Yu. Nikiforov, L. Li, P. Vanraes, N. Britun, R. Snyders, X.P. Lu, C. Leys : Eur. Phys. J. D 66 (2012) 281. [7] J. Voráč, P. Dvovrák, V. Procházka

  5. One- or Two-Electron Water Oxidation, Hydroxyl Radical, or H2O2 Evolution.

    PubMed

    Siahrostami, Samira; Li, Guo-Ling; Viswanathan, Venkatasubramanian; Nørskov, Jens K

    2017-02-27

    Electrochemical or photoelectrochemcial oxidation of water to form hydrogen peroxide (H2O2) or hydroxyl radicals ((•)OH) offers a very attractive route to water disinfection, and the first process could be the basis for a clean way to produce hydrogen peroxide. A major obstacle in the development of effective catalysts for these reactions is that the electrocatalyst must suppress the thermodynamically favored four-electron pathway leading to O2 evolution. We develop a thermochemical picture of the catalyst properties that determine selectivity toward the one, two, and four electron processes leading to (•)OH, H2O2, and O2.

  6. One- or two-electron water oxidation, hydroxyl radical, or H2O2 evolution

    DOE PAGES

    Siahrostami, Samira; Li, Guo -Ling; Viswanathan, Venkatasubramanian; ...

    2017-02-23

    Electrochemical or photoelectrochemcial oxidation of water to form hydrogen peroxide (H2O2) or hydroxyl radicals (•OH) offers a very attractive route to water disinfection, and the first process could be the basis for a clean way to produce hydrogen peroxide. A major obstacle in the development of effective catalysts for these reactions is that the electrocatalyst must suppress the thermodynamically favored four-electron pathway leading to O2 evolution. Here, we develop a thermochemical picture of the catalyst properties that determine selectivity toward the one, two, and four electron processes leading to •OH, H2O2, and O2.

  7. A high performance liquid chromatography system for quantification of hydroxyl radical formation by determination of dihydroxy benzoic acids.

    PubMed

    Owen, R W; Wimonwatwatee, T; Spiegelhalder, B; Bartsch, H

    1996-08-01

    The hypoxanthine/xanthine oxidase enzyme system is known to produce the superoxide ion and hydrogen peroxide during the hydroxylation of hypoxanthine via xanthine to uric acid. When chelated iron is included in this system, superoxide reduces iron (III) to iron(II) and the iron(II)-chelate further reacts with hydrogen peroxide to form the highly reactive hydroxyl radical. Because of the limitations of colourimetric and spectrophotometric techniques by which, to date, the mechanisms of hydroxyl radical formation in the hypoxanthine/xanthine oxidase system have been monitored, a high performance liquid chromatography method utilizing the ion-pair reagent tetrabutylammonium hydroxide and salicylic acid as an aromatic probe for quantification of hydroxyl radical formation was set up. In the hypoxanthine/xanthine oxidase system the major products of hydroxyl radical attack on salicylic acid were 2,5-dihydroxy benzoic acid and 2,3-dihydroxy benzoic acid in the approximate ratio of 5:1. That the hydroxyl radical is involved in the hydroxylation of salicylic acid in this system was demonstrated by the potency especially of dimethyl sulphoxide, butanol and ethanol as scavengers. Phytic acid, which is considered to be an important protective dietary constituent against colorectal cancer, inhibited hydroxylation of salicylic acid at a concentration one order of magnitude lower than the classical scavengers, but was only effective in the absence of EDTA. The method has been applied to the study of free radical generation in faeces, and preliminary results indicate that the faecal flora are able to produce reactive oxygen species in abundance.

  8. [Development of a chemical ionization time-of-flight mass spectrometer for continuous measurements of atmospheric hydroxyl radical].

    PubMed

    Dou, Jian; Hua, Lei; Hou, Ke-Yong; Jiang, Lei; Xie, Yuan-Yuan; Zhao, Wu-Duo; Chen, Ping; Wang, Wei-Guo; Di, Tian; Li, Hai-Yang

    2014-05-01

    A home-made chemical ionization time-of-flight mass spectrometer (TOFMS) has been developed for continuous measurements of atmospheric hydroxyl radical. Based on the atmospheric pressure chemical ionization technique, an ionization source with orthogonal dual tube structure was adopted in the instrument, which minimized the interference between the reagent gas ionization and the titration reaction. A 63Ni radioactive source was fixed inside one of the orthogonal tubes to generate reactant ion of NO(-)(3) from HNO3 vapor. Hydroxyl radical was first titrated by excess SO2 to form equivalent concentrations of H2SO4 in the other orthogonal tube, and then reacted with NO(-)(3) ions in the chemical ionization chamber, leading to HSO(-)(4) formation. The concentration of atmospheric hydroxyl radical can be directly calculated by measuring the intensities of the HSOj product ions and the NO(-)(3) reactant ions. The analytical capability of the instrument was demonstrated by measuring hydroxyl radical in laboratory air, and the concentration of the hydroxyl radical in the investigated air was calculated to be 1.6 x 106 molecules*cm ', based on 5 seconds integration. The results have shown that the instrument is competent for in situ continuous measurements of atmospheric trace radical.

  9. Kinetic behavior of the reaction between hydroxyl radical and the SV40 minichromosome

    NASA Astrophysics Data System (ADS)

    Ly, A.; Aguilera, J. A.; Milligan, J. R.

    2007-06-01

    Aqueous solutions containing the minichromosomal form of the virus SV40 and the radical scavenger DMSO were subjected to γ-irradiation, and the resulting formation of single-strand breaks (SSB) was quantified. Under the irradiation conditions, most SSBs were produced as a consequence of hydroxyl radical ( rad OH) reactions. By controlling the competition between DMSO and the viral DNA substrate for rad OH, we are able to estimate the rate coefficient for the reaction of rad OH with the SV40 minichromosome. The results cannot be described adequately by homogeneous competition kinetics, but it is possible to describe the rate coefficient for the reaction as a function of the scavenging capacity of the solution. The experimentally determined rate coefficient lies in the range 1×10 9-2×10 9 L mol -1 s -1 at 10 7 s -1, and increases with increasing scavenging capacity.

  10. Inelastic scattering of hydroxyl radicals with helium and argon by velocity-map imaging.

    PubMed

    Sarma, Gautam; Marinakis, Sarantos; ter Meulen, J J; Parker, David H; McKendrick, Kenneth G

    2012-12-01

    The hydroxyl radical (OH) is one of the most interesting molecules in molecular dynamics. In particular, inelastic collisions of free radicals such as OH are profoundly important in environments ranging from combustion to astrochemistry. However, measuring the velocities of OH molecules in specific internal quantum states has proven to be very difficult. A method that can provide this important information is velocity-map imaging. Although this technique is very widely applicable in principle, it does require a sensitive and selective laser-ionization scheme. Here we show that, under the right conditions, velocity-map imaging can be applied to the study of the inelastic scattering of OH using crossed-molecular-beam methods. We measure fully quantum-state-specified product angular distributions for OH collisions with helium and argon. The agreement between exact close-coupling quantum scattering calculations on ab initio potential energy surfaces and experimental data is generally very satisfactory, except for scattering in the most forward directions.

  11. Glycosphingolipids and oxidative stress: evaluation of hydroxyl radical oxidation of galactosyl and lactosylceramides using mass spectrometry.

    PubMed

    Couto, Daniela; Santinha, Deolinda; Melo, Tânia; Ferreira-Fernandes, Emanuel; Videira, Romeu A; Campos, Ana; Fardilha, Margarida; Domingues, Pedro; Domingues, M Rosário M

    2015-10-01

    Galactosylceramide (GalCer) and lactosylceramide (LacCer) are structural and signaling lipids, playing important roles in signal transduction and cell adhesion. They are especially abundant in the nervous system and in important components of the myelin sheath. Although neurodegenerative disorders are associated with increased oxidative stress and lipid oxidation, the connection between oxidative stress and glycosphingolipid modification has been scarcely addressed. In this study, we aimed to characterize the structural changes caused by the hydroxyl radical to GalCer and LacCer molecular species using electrospray ionization mass spectrometry (ESI-MS and MS/MS) and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS(n)). ESI-MS and LC-MS spectra of 24:1GalCer and 24:1LacCer after free radical oxidation showed the formation of new species, which were identified as keto, hydroxyl and hydroperoxy derivatives, arising from modification in the mono unsaturated fatty acyl chain. Formation of ceramide and oxidized ceramides was also observed as a result of 24:1GalCer and 24:1LacCer radical oxidation. 24:1GlcCer (glucosylceramide) was detected after LacCer oxidation, probably due to oxidative cleavage of lactosyl moiety. This study shows that glycosphingolipids are prone to radical induced oxidation, which can be one of the causes of the increased ceramides content and pro apoptotic events during oxidative conditions and neurodegeneration. This MS study will support the future identification of oxidized galactosyl- and lactosylceramide species in sphingolipidomic studies applied to biological samples related with oxidative conditions.

  12. Removal of 2-MIB and geosmin using UV/persulfate: contributions of hydroxyl and sulfate radicals.

    PubMed

    Xie, Pengchao; Ma, Jun; Liu, Wei; Zou, Jing; Yue, Siyang; Li, Xuchun; Wiesner, Mark R; Fang, Jingyun

    2015-02-01

    2-methylisoborneol (2-MIB) and geosmin are two odor-causing compounds that are difficult to remove and the cause of many consumer complaints. In this study, we assessed the degradation of 2-MIB and geosmin using a UV/persulfate process for the first time. The results showed that both 2-MIB and geosmin could be degraded effectively using this process. The process was modeled based on steady-state assumption with respect to the odor-causing compounds and either hydroxyl or sulfate radicals. The second order rate constants for 2-MIB and geosmin reacting with the sulfate radical (SO4(-)) were estimated to be (4.2 ± 0.6) × 10(8) M(-1)s(-1) and (7.6 ± 0.6) × 10(8) M(-1)s(-1) respectively at a pH of 7.0. The contributions of the hydroxyl radical (OH) to 2-MIB and geosmin degradation were 3.5 times and 2.0 times higher, respectively, than the contribution from SO4(-) in Milli-Q water with 2 mM phosphate buffer at pH 7.0. The pseudo-first-order rate constants (ko(s)) of both 2-MIB and geosmin increased with increasing dosages of persulfate. Although pH did not affect the degradation of 2-MIB and geosmin directly, different scavenging effects of hydrogen phosphate and dihydrogen phosphate resulted in higher values of ko(s) for both 2-MIB and geosmin in acidic condition. Bicarbonate and natural organic matter (NOM) inhibited the degradation of both 2-MIB and geosmin dramatically through consuming OH and SO4(-) and were likely to be the main radical scavengers in natural waters when using UV/persulfate process to control 2-MIB and geosmin.

  13. Damage to the oxygen-evolving complex by superoxide anion, hydrogen peroxide, and hydroxyl radical in photoinhibition of photosystem II.

    PubMed

    Song, Yu Guang; Liu, Bin; Wang, Lan Fen; Li, Mai He; Liu, Yang

    2006-10-01

    Under strong illumination of a photosystem II (PSII) membrane, endogenous superoxide anion, hydrogen peroxide, and hydroxyl radical were successively produced. These compounds then cooperatively resulted in a release of manganese from the oxygen-evolving complex (OEC) and an inhibition of oxygen evolution activity. The OEC inactivation was initiated by an acceptor-side generated superoxide anion, and hydrogen peroxide was most probably responsible for the transportation of reactive oxygen species (ROS) across the PSII membrane from the acceptor-side to the donor-side. Besides ROS being generated in the acceptor-side induced manganese loss; there may also be a ROS-independent manganese loss in the OEC of PSII. Both superoxide anion and hydroxyl radical located inside the PSII membrane were directly identified by a spin trapping-electron spin resonance (ESR) method in combination with a lipophilic spin trap, 5-(diethoxyphosphoryl)-5-phenethyl-1-pyrroline N-oxide (DEPPEPO). The endogenous hydrogen peroxide production was examined by oxidation of thiobenzamide.

  14. Efficient degradation of atrazine by magnetic porous copper ferrite catalyzed peroxymonosulfate oxidation via the formation of hydroxyl and sulfate radicals.

    PubMed

    Guan, Ying-Hong; Ma, Jun; Ren, Yue-Ming; Liu, Yu-Lei; Xiao, Jia-Yue; Lin, Ling-qiang; Zhang, Chen

    2013-09-15

    Magnetic porous copper ferrite (CuFe2O4) showed a notable catalytic activity to peroxymonosulfate (PMS). More than 98% of atrazine was degraded within 15 min at 1 mM PMS and 0.1 g/L CuFe2O4. In contrast, CuFe2O4 exhibited no obvious catalytic activity to peroxodisulfate or H2O2. Several factors affecting the catalytic performance of PMS/CuFe2O4 were investigated. Results showed that the catalytic degradation efficiency of atrazine increased with PMS and CuFe2O4 doses, but decreased with the increase of natural organic matters concentration. The catalytic oxidation also showed a dependence on initial pH. The presence of bicarbonate stimulated atrazine degradation by PMS/CuFe2O4 at low concentrations but inhibited the degradation at high concentrations. Furthermore, the reactive species for atrazine degradation in PMS/CuFe2O4 system were identified as hydroxyl radical (HO) and sulfate radical (SO4(·-)) through competition reactions of atrazine and nitrobenzene, instead of commonly used alcohol scavenging, which was not a reliable method in metal oxide catalyzed oxidation. Surface hydroxyl groups of CuFe2O4 were a critical part in radical generation and the copper on CuFe2O4 surface was an active site to catalyze PMS. The catalytic degradation of atrazine by PMS/CuFe2O4 was also effective under the background of actual waters.

  15. Sugars as hydroxyl radical scavengers: proof-of-concept by studying the fate of sucralose in Arabidopsis.

    PubMed

    Matros, Andrea; Peshev, Darin; Peukert, Manuela; Mock, Hans-Peter; Van den Ende, Wim

    2015-06-01

    Substantial formation of reactive oxygen species (ROS) is inevitable in aerobic life forms. Due to their extremely high reactivity and short lifetime, hydroxyl radicals are a special case, because cells have not developed enzymes to detoxify these most dangerous ROS. Thus, scavenging of hydroxyl radicals may only occur by accumulation of higher levels of simple organic compounds. Previous studies have demonstrated that plant-derived sugars show hydroxyl radical scavenging capabilities during Fenton reactions with Fe(2+) and hydrogen peroxide in vitro, leading to formation of less detrimental sugar radicals that may be subject of regeneration to non-radical carbohydrates in vivo. Here, we provide further evidence for the occurrence of such radical reactions with sugars in planta, by following the fate of sucralose, an artificial analog of sucrose, in Arabidopsis tissues. The expected sucralose recombination and degradation products were detected in both normal and stressed plant tissues. Oxidation products of endogenous sugars were also assessed in planta for Arabidopsis and barley, and were shown to increase in abundance relative to the non-oxidized precursor during oxidative stress conditions. We concluded that such non-enzymatic reactions with hydroxyl radicals form an integral part of plant antioxidant mechanisms contributing to cellular ROS homeostasis, and may be more important than generally assumed. This is discussed in relation to the recently proposed roles for Fe(2+) and hydrogen peroxide in processes leading to the origin of metabolism and the origin of life.

  16. Synthesis and radical-scavenging activity of a dimethyl catechin analogue.

    PubMed

    Imai, Kohei; Nakanishi, Ikuo; Ohno, Akiko; Kurihara, Masaaki; Miyata, Naoki; Matsumoto, Ken-Ichiro; Nakamura, Asao; Fukuhara, Kiyoshi

    2014-06-01

    Catechin analogue 1 with methyl substituents ortho to the catechol hydroxyl groups was synthesized to improve the antioxidant ability of (+)-catechin. The synthetic scheme involved a solid acid catalyzed Friedel-Crafts coupling of a cinnamyl alcohol derivative to 3,5-dibenzyloxyphenol followed by hydroxylation and then cyclization through an intermediate orthoester. The antioxidative radical scavenging activity of 1 against galvinoxyl radical, an oxyl radical, was found to be 28-fold more potent than (+)-catechin.

  17. Photochemical formation of hydroxyl radical in red-soil-polluted seawater - effects of dissolved organic compounds

    NASA Astrophysics Data System (ADS)

    Uehara, M.; Arakaki, T.

    2006-12-01

    Development of pineapple farmlands and construction of recreational facilities caused runoff of red soil into the coastal ocean (locally termed as red soil pollution) in the north of Okinawa Island, Japan. Red soil is acidic and contains a few percent of iron oxide. We were interested in the formation of hydroxyl radical (·OH), the most potent oxidant in the environment, from the photo-Fenton reaction (reaction between Fe(II) and HOOH) in red-soil-polluted seawater. Various artificial seawater solutions were prepared by adding red soil, HOOH, and/or humic acid to clean seawater, and were used for photochemical experiments. Commercially available humic acid was used to represent natural organic compounds. All the solutions were filtered through 0.45 micron filter before conducting photochemical experiments. Comparisons among the solutions indicated that dissolved chemicals from the red-soil only slightly increased the OH radical photoformation. Photoformation rates of OH radicals of the HOOH + red soil solutions were similar to the calculated rates from direct photolysis of HOOH. Furthermore, addition of humic acid to the HOOH + red soil solutions did not significantly enhance the photo-Fenton reaction, suggesting that Fe(II), even if it had been formed, did not react with HOOH to form OH radicals at detectable level in seawater.

  18. Atmospheric reactions of gaseous mercury with ozone and hydroxyl radical: Kinetics and product studies

    NASA Astrophysics Data System (ADS)

    Biswajit, P.; Parisa, A. A.

    2003-05-01

    The dominant form of mercury in the atmosphere is Hg^0. The oxidation processes are of great importance since oxidized mercury undergoes deposition and can become subject to bioaccumulation. Experimental data on the gaseous reactions of elemental mercury are very limited with compare to the reactions of Hg^0 in solutions. We herein carried out kinetic and product studies on the reactions of gaseous Hg^0 with O3 and hydroxyl radical (HO) under near atmospheric pressure (750 ± 1 Torr) and room temperature (298 ± 1 K) in air and N2. O3 was produced in a silent discharge generator (OL 100/SB). Hydroxyl radicals were produced from the photolysis of isopropyl nitrite in the presence of NO. Kinetics of the reactions with O3/HO was studied using absolute and relative techniques by gas chromatography with mass spectroscopic detection (GCMS). The gas phase reaction between elemental Hg^0 with O3 has been studied in different surface-to-volume (s/v) ratios, and evidence for heterogeneous reactions was observed. Existence of mercuric oxide, Hg^0 by the reaction of atomic Hg^0 with O3 has been determined in the gas phase from the suspended aerosols using high temperature mass spectrometry.

  19. Isoprenoid Alcohols are Susceptible to Oxidation with Singlet Oxygen and Hydroxyl Radicals.

    PubMed

    Komaszylo Née Siedlecka, Joanna; Kania, Magdalena; Masnyk, Marek; Cmoch, Piotr; Lozinska, Iwona; Czarnocki, Zbigniew; Skorupinska-Tudek, Karolina; Danikiewicz, Witold; Swiezewska, Ewa

    2016-02-01

    Isoprenoids, as common constituents of all living cells, are exposed to oxidative agents--reactive oxygen species, for example, singlet oxygen or hydroxyl radicals. Despite this fact, products of oxidation of polyisoprenoids have never been characterized. In this study, chemical oxidation of isoprenoid alcohols (Prenol-2 and -10) was performed using singlet oxygen (generated in the presence of hydrogen peroxide/molybdate or upon photochemical reaction in the presence of porphyrin), oxygen (formed upon hydrogen peroxide dismutation) or hydroxyl radical (generated by the hydrogen peroxide/sonication, UV/titanium dioxide or UV/hydrogen peroxide) systems. The structure of the obtained products, hydroxy-, peroxy- and heterocyclic derivatives, was studied with the aid of mass spectrometry (MS) and nuclear magnetic resonance (NMR) methods. Furthermore, mass spectrometry with electrospray ionization appeared to be a useful analytical tool to detect the products of oxidation of isoprenoids (ESI-MS analysis), as well as to establish their structure on the basis of the fragmentation spectra of selected ions (ESI-MS/MS analysis). Taken together, susceptibility of polyisoprenoid alcohols to various oxidizing agents was shown for the first time.

  20. Chemical probing of RNA with the hydroxyl radical at single-atom resolution.

    PubMed

    Ingle, Shakti; Azad, Robert N; Jain, Swapan S; Tullius, Thomas D

    2014-11-10

    While hydroxyl radical cleavage is widely used to map RNA tertiary structure, lack of mechanistic understanding of strand break formation limits the degree of structural insight that can be obtained from this experiment. Here, we determine how individual ribose hydrogens of sarcin/ricin loop RNA participate in strand cleavage. We find that substituting deuterium for hydrogen at a ribose 5'-carbon produces a kinetic isotope effect on cleavage; the major cleavage product is an RNA strand terminated by a 5'-aldehyde. We conclude that hydroxyl radical abstracts a 5'-hydrogen atom, leading to RNA strand cleavage. We used this approach to obtain structural information for a GUA base triple, a common tertiary structural feature of RNA. Cleavage at U exhibits a large 5' deuterium kinetic isotope effect, a potential signature of a base triple. Others had noted a ribose-phosphate hydrogen bond involving the G 2'-OH and the U phosphate of the GUA triple, and suggested that this hydrogen bond contributes to backbone rigidity. Substituting deoxyguanosine for G, to eliminate this hydrogen bond, results in a substantial decrease in cleavage at G and U of the triple. We conclude that this hydrogen bond is a linchpin of backbone structure around the triple.

  1. UVA-induced reset of hydroxyl radical ultradian rhythm improves temporal lipid production in Chlorella vulgaris.

    PubMed

    Balan, Ranjini; Suraishkumar, G K

    2014-01-01

    We report for the first time that the endogenous, pseudo-steady-state, specific intracellular levels of the hydroxyl radical (si-OH) oscillate in an ultradian fashion (model system: the microalga, Chlorella vulgaris), and also characterize the various rhythm parameters. The ultradian rhythm in the endogenous levels of the si-OH occurred with an approximately 6 h period in the daily cycle of light and darkness. Further, we expected that the rhythm reset to a shorter period could rapidly switch the cellular redox states that could favor lipid accumulation. We reset the endogenous rhythm through entrainment with UVA radiation, and generated two new ultradian rhythms with periods of approximately 2.97 h and 3.8 h in the light phase and dark phase, respectively. The reset increased the window of maximum lipid accumulation from 6 h to 12 h concomitant with the onset of the ultradian rhythms. Further, the saturated fatty acid content increased approximately to 80% of total lipid content, corresponding to the peak maxima of the hydroxyl radical levels in the reset rhythm.

  2. Hydroxyl radical scavenging mechanism of human erythrocytes by quercetin-germanium (IV) complex.

    PubMed

    Li, Sheng-Pu; Xie, Wei-Ling; Cai, Huai-Hong; Cai, Ji-Ye; Yang, Pei-Hui

    2012-08-30

    Quercetin is a popular flavonoid in plant foods, herbs, and dietary supplement. Germanium, a kind of trace elements, can enhance the body immunity. This study investigated the hydroxyl-radical-scavenging mechanism of the quercertin-germanium (IV) (Qu-Ge) complex to human erythrocytes, especially the effects on ultrastructure and mechanical properties of cell membrane, plasma membrane potential and intracellular free Ca(2+) concentration. Results showed that QuGe(2), a kind of the Qu-Ge complex, could reduce the oxidative damage of erythrocytes, change the cell-surface morphology, and partly recover the disruption of plasma membrane potential and intracellular free Ca(2+) level. Atomic force microscopy (AFM) was used to characterize the changes of the cell morphology, cell-membrane ultrastructure and biophysical properties at nanoscalar level. QuGe(2) has triggered the antioxidative factor to inhibit cellular damage. These results can improve the understanding of hydroxyl-radical-scavenging mechanism of human erythrocytes induced by the Qu-Ge complex, which can be potentially developed as a new antioxidant for treatment of oxidative damage.

  3. Sulfate radical-based water treatment in presence of chloride: formation of chlorate, inter-conversion of sulfate radicals into hydroxyl radicals and influence of bicarbonate.

    PubMed

    Lutze, Holger V; Kerlin, Nils; Schmidt, Torsten C

    2015-04-01

    Sulfate radical (SO4(-)) based oxidation is discussed as a potential water treatment option and is already used in ground water remediation. However, the complex SO4(-) chemistry in various matrices is poorly understood. In that regard, the fast reaction of SO4(-) with Cl(-) is of high importance since Cl(-) belongs to the main constituents in aqueous environments. This reaction yields chlorine atoms (Cl) as primary products. Cl initiate a cascade of subsequent reactions with a pH dependent product pattern. At low pH (<5) formation of chlorine derived oxidation products such as chlorate (ClO3(-)) is favoured. This is undesired because ClO3(-) may reveal adverse effects on the environment and human health. At pH > 5 Cl mainly react with water yielding hydroxyl radicals. Thus, at moderate Cl(-) concentrations (mM range) the SO4(-)-based process may be converted into a conventional (hydroxyl radical -based) advanced oxidation process. The conversion of SO4(-) into OH, however, is interrupted in presence of bicarbonate by scavenging of Cl.

  4. Possible involvement of hydroxyl radical on the stimulation of tetrahydrobiopterin synthesis by hydrogen peroxide and peroxynitrite in vascular endothelial cells.

    PubMed

    Shimizu, Shunichi; Ishii, Masakazu; Miyasaka, Yoshiyuki; Wajima, Teruaki; Negoro, Takaharu; Hagiwara, Tamio; Kiuchi, Yuji

    2005-04-01

    We recently described that hydrogen peroxide (H2O2) stimulates the synthesis of tetrahydrobiopterin (BH4) through the induction of the rate-limiting enzyme GTP-cyclohydrolase I (GTPCH), and increases tetrahydrobiopterin content in vascular endothelial cells. Tetrahydrobiopterin is easily oxidized by peroxynitrite (ONOO-), but not by hydrogen peroxide. The aim of this study was to determine the effect of hydroxyl radical and peroxynitrite, which are both toxic biological oxidants, on tetrahydrobiopterin synthesis and the regulation of its content in vascular endothelial cells. In the cell-free assay system, tetrahydrobiopterin was rapidly oxidized by the hydroxyl radical and peroxynitrite, but not by hydrogen peroxide. However, the addition of not only hydrogen peroxide but also the hydroxyl radical and peroxynitrite to vascular endothelial cells transiently decreased tetrahydrobiopterin content, and then markedly increased its content. Interestingly, total biopterin content was also decreased by early treatment with oxidants. Moreover, oxidants induced the expression of GTP-cyclohydrolase I, and the increase of the tetrahydrobiopterin content was blocked by the treatment with GTP-cyclohydrolase I inhibitor. Both the hydrogen peroxide- and peroxynitrite-induced increases in tetrahydrobiopterin content and findings suggest that not only hydrogen peroxide but also the hydroxyl radical and peroxynitrite stimulates tetrahydrobiopterin synthesis through GTP-cyclohydrolase I expression, and that the hydroxyl radical plays a central role in the stimulation of tetrahydrobiopterin synthesis. Moreover, the transient decrease in BH4 to tetrahydrobiopterin.

  5. Bactericidal effect of hydroxyl radicals generated from a low concentration hydrogen peroxide with ultrasound in endodontic treatment.

    PubMed

    Kobayashi, Yoshimi; Hayashi, Makoto; Yoshino, Fumihiko; Tamura, Muneaki; Yoshida, Ayaka; Ibi, Haruna; Lee, Masaichi-Chang-Il; Ochiai, Kuniyasu; Ogiso, Bunnai

    2014-05-01

    One approach to enhance the disinfection of root canals in endodontic treatment is ultrasonic irrigation with sodium hypochlorite. Reactive oxygen species, such as hydroxyl radical, are generated by biological defense systems to kill invading bacteria. Ultrasonic irrigation with hydrogen peroxide may be a promising option to increase hydroxyl radical generation. We examined the bactericidal effects of hydroxyl radical generated from low concentration hydrogen peroxide with ultrasound in vitro. An ultrasonic tip was submerged in 0.5 or 1.0 M hydrogen peroxide in a microfuge tube. hydrogen peroxide was irradiated with the ultrasound, the tip of which was maintained centered in the tube to mimic ultrasonic irrigation. Hydroxyl radical generation was assessed by electron spin resonance spectroscopy. Subsequently, Enterococcus faecalis suspension in hydrogen peroxide was prepared and irradiated as described above. Bactericidal effects were assessed by viable counting. Electron spin resonance measurements showed that hydroxyl radical generation increased significantly in a time- and dose-dependent manner (two-way analysis of variance and Tukey's test, p<0.05). Moreover, the bactericidal effects of hydrogen peroxide against Enterococcus faecalis were enhanced by ultrasonic irradiation in a time- and dose-dependent manner. These results suggest that ultrasonic irrigation in the presence of low concentration hydrogen peroxide can serve as a disinfection strategy in endodontic treatment.

  6. Vitamin C (ascorbic acid) induced hydroxyl radical formation in copper contaminated household drinking water: role of bicarbonate concentration.

    PubMed

    Jansson, Patric J; Asplund, Klara U M; Mäkelä, Johanna C; Lindqvist, Christer; Nordström, Tommy

    2003-08-01

    We have previously shown that Vitamin C (ascorbic acid) can trigger hydroxyl radical formation in copper contaminated household drinking water. We report here that the capacity of ascorbic acid to catalyze hydroxyl radical generation in the drinking water samples is strongly dependent on the bicarbonate concentration (buffer capacity and pH) of the samples. We found that at least 50 mg/l bicarbonate was required in the water samples to maintain the pH over 5.0 after ascorbic acid addition. At this pH, that is higher than the pKa1 4.25 of ascorbic acid, a hydroxyl radical generating redox cycling reaction involving the mono-anion of vitamin C and copper could take place. The ascorbic acid induced hydroxyl radical generating reaction could easily be mimicked in Milli-Q water by supplementing the water with copper and bicarbonate. Our results demonstrate that ascorbic acid can induce a pH dependent hydroxyl radical generating reaction in copper contaminated household tap water that is buffered with bicarbonate. The impact of consuming ascorbic acid together with copper and bicarbonate containing drinking water on human health is discussed.

  7. Hydroxyl radical mediates cisplatin-induced apoptosis in human hair follicle dermal papilla cells and keratinocytes through Bcl-2-dependent mechanism.

    PubMed

    Luanpitpong, Sudjit; Nimmannit, Ubonthip; Chanvorachote, Pithi; Leonard, Stephen S; Pongrakhananon, Varisa; Wang, Liying; Rojanasakul, Yon

    2011-08-01

    Induction of massive apoptosis of hair follicle cells by chemotherapy has been implicated in the pathogenesis of chemotherapy-induced alopecia (CIA), but the underlying mechanisms of regulation are not well understood. The present study investigated the apoptotic effect of cisplatin in human hair follicle dermal papilla cells and HaCaT keratinocytes, and determined the identity and role of specific reactive oxygen species (ROS) involved in the process. Treatment of the cells with cisplatin induced ROS generation and a parallel increase in caspase activation and apoptotic cell death. Inhibition of ROS generation by antioxidants inhibited the apoptotic effect of cisplatin, indicating the role of ROS in the process. Studies using specific ROS scavengers further showed that hydroxyl radical, but not hydrogen peroxide or superoxide anion, is the primary oxidative species responsible for the apoptotic effect of cisplatin. Electron spin resonance studies confirmed the formation of hydroxyl radicals induced by cisplatin. The mechanism by which hydroxyl radical mediates the apoptotic effect of cisplatin was shown to involve down-regulation of the anti-apoptotic protein Bcl-2 through ubiquitin-proteasomal degradation. Bcl-2 was also shown to have a negative regulatory role on hydroxyl radical. Together, our results indicate an essential role of hydroxyl radical in cisplatin-induced cell death of hair follicle cells through Bcl-2 regulation. Since CIA is a major side effect of cisplatin and many other chemotherapeutic agents with no known effective treatments, the knowledge gained from this study could be useful in the design of preventive treatment strategies for CIA through localized therapy without compromising the chemotherapy efficacy.

  8. Comparison of the reactivity of ibuprofen with sulfate and hydroxyl radicals: An experimental and theoretical study.

    PubMed

    Yang, Zhihui; Su, Rongkui; Luo, Shuang; Spinney, Richard; Cai, Meiqiang; Xiao, Ruiyang; Wei, Zongsu

    2017-07-15

    Hydroxyl radical ((•)OH) and sulfate radical anion (SO4(•-)) based advanced oxidation technologies (AOTs) are effective methods to treat trace organic contaminants (TrOCs) in engineered waters. Although both technologies result in the same overall removal of TrOCs, the mechanistic differences between these two radicals involved in the oxidation of TrOCs remain unclear. In this study, we experimentally examined the degradation kinetics of neutral ibuprofen (IBU), a representative TrOC, by (•)OH and SO4(•-) at pH3 in UV/H2O2 and UV/persulfate systems, respectively. The second-order rate constants (k) of IBU with (•)OH and SO4(•-) were determined to be 3.43±0.06×10(9) and 1.66±0.12×10(9)M(-1)s(-1), respectively. We also theoretically calculated the thermodynamic and kinetic behaviors for reactions of IBU with (•)OH and SO4(•-) using the density functional theory (DFT) M06-2X method with 6-311++G** basis set. The results revealed that H-atom abstraction is the most favorable pathway for both (•)OH and SO4(•-), but due to the steric hindrance SO4(•-) exhibits significantly higher energy barriers than (•)OH. The theoretical calculations corroborate our experimental observation that SO4(•-) has a smaller k value than (•)OH in reacting with IBU. These comparative results are of fundamental and practical importance in understanding the electrophilic interactions between radicals and IBU molecules, and to help select preferred radical oxidation processes for optimal TrOCs removal in engineered waters.

  9. Iron oxychloride (FeOCl): an efficient Fenton-like catalyst for producing hydroxyl radicals in degradation of organic contaminants.

    PubMed

    Yang, Xue-jing; Xu, Xi-meng; Xu, Jing; Han, Yi-fan

    2013-10-30

    An iron oxychloride (FeOCl) catalyst was developed for oxidative degradation of persistent organic compounds in aqueous solutions. Exceptionally high activity for the production of hydroxyl radical (OH·) by H2O2 decomposition was achieved, being 2-4 orders of magnitudes greater than that over other Fe-based heterogeneous catalysts. The relationship of catalyst structure and performance has been established by using multitechniques, such as XRD, HRTEM, and EPR. The unique structural configuration of iron atoms and the reducible electronic properties of FeOCl are responsible for the excellent activity. This study paves the way toward the rational design of relevant catalysts for applications, such as wastewater treatment, soil remediation, and other emerging environmental problems.

  10. Moringa oleifera Lam. seed extract prevents fat diet induced oxidative stress in mice and protects liver cell-nuclei from hydroxyl radical mediated damage.

    PubMed

    Das, Nilanjan; Ganguli, Debdutta; Dey, Sanjit

    2015-12-01

    High fat diet (HFD) prompts metabolic pattern inducing reactive oxygen species (ROS) production in mitochondria thereby triggering multitude of chronic disorders in human. Antioxidants from plant sources may be an imperative remedy against this disorder. However, it requires scientific validation. In this study, we explored if (i) Moringa oleifera seed extract (MoSE) can neutralize ROS generated in HFD fed mice; (ii) protect cell-nuclei damage developed by Fenton reaction in vitro. Swiss mice were fed with HFD to develop oxidative stress model (HFD group). Other groups were control, seed extract alone treated, and MoSE simultaneously (HS) treated. Treatment period was of 15 days. Antioxidant enzymes with tissue nitrite content (TNC) and lipid peroxidation (LPO) were estimated from liver homogenate. HS group showed significantly higher (P < 0.05) superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH) activity, and ferric reducing antioxidant power (FRAP) compared to only HFD fed group. Further, TNC and LPO decreased significantly (P < 0.05) in HS group compared to HFD fed group. MoSE also protected hepatocytes nuclei from the hydroxyl radicals generated by Fenton reaction. MoSE was found to be polyphenol rich with potent reducing power, free radicals and hydroxyl radicals scavenging activity. Thus, MoSE exhibited robust antioxidant prospective to neutralize ROS developed in HFD fed mice and also protected the nuclei damage from hydroxyl radicals. Hence, it can be used as herbal medication against HFD induced ROS mediated disorders.

  11. Kinetic Study of Hydroxyl and Sulfate Radical-Mediated Oxidation of Pharmaceuticals in Wastewater Effluents.

    PubMed

    Lian, Lushi; Yao, Bo; Hou, Shaodong; Fang, Jingyun; Yan, Shuwen; Song, Weihua

    2017-02-13

    Advanced oxidation processes (AOPs), such as hydroxyl radical (HO(•))- and sulfate radical (SO4(•-))-mediated oxidation, are alternatives for the attenuation of pharmaceuticals and personal care products (PPCPs) in wastewater effluents. However, the kinetics of these reactions needs to be investigated. In this study, kinetic models for 15 PPCPs were built to predict the degradation of PPCPs in both HO(•)- and SO4(•-)-mediated oxidation. In the UV/H2O2 process, a simplified kinetic model involving only steady state concentrations of HO(•) and its biomolecular reaction rate constants is suitable for predicting the removal of PPCPs, indicating the dominant role of HO(•) in the removal of PPCPs. In the UV/K2S2O8 process, the calculated steady state concentrations of CO3(•-) and bromine radicals (Br(•), Br2(•-) and BrCl(•-)) were 600-fold and 1-2 orders of magnitude higher than the concentrations of SO4(•-), respectively. The kinetic model, involving both SO4(•-) and CO3(•-) as reactive species, was more accurate for predicting the removal of the 9 PPCPs, except for salbutamol and nitroimidazoles. The steric and ionic effects of organic matter toward SO4(•-) could lead to overestimations of the removal efficiencies of the SO4(•-)-mediated oxidation of nitroimidazoles in wastewater effluents.

  12. An ab initio investigation of possible intermediates in the reaction of the hydroxyl and hydroperoxyl radicals

    NASA Technical Reports Server (NTRS)

    Jackels, C. F.

    1985-01-01

    Ab initio quantum chemical techniques are used to investigate covalently-bonded and hydrogen-bonded species that may be important intermediates in the reaction of hydroxyl and hydroperoxyl radicals. Stable structures of both types are identified. Basis sets of polarized double zeta quality and large scale configuration interaction wave functions are utilized. Based on electronic energies, the covalently bonded HOOOH species is 26.4 kcal/mol more stable than the OH and HO2 radicals. Similarly, the hydrogen bonded HO---HO2 species has an electronic energy 4.7 kcal/mol below that of the component radicals, after correction is made for the basis set superposition error. The hydrogen bonded form is planar, possesses one relatively normal hydrogen bond, and has the lowest energy 3A' and 1A' states that are essentially degenerate. The 1A" and 3A" excited states produced by rotation of the unpaired OH electron into the molecular plane are very slightly bound.

  13. Theoretical study of the oxidation mechanisms of naphthalene initiated by hydroxyl radicals: the H abstraction pathway.

    PubMed

    Shiroudi, Abolfazl; Deleuze, Michael S

    2014-05-22

    Reaction mechanisms for the initial stages of naphthalene oxidation at high temperatures (T ≥ 600 K) have been studied theoretically using density functional theory along with various exchange-correlation functionals, as well as the benchmark CBS-QB3 quantum chemical approach. These stages correspond to the removal of hydrogen atoms by hydroxyl radical and the formation thereby of 1- and 2-naphthyl radicals. Bimolecular kinetic rate constants were estimated by means of transition state theory. The excellent agreement with the available experimental kinetic rate constants demonstrates that a two-step reaction scheme prevails. Comparison with results obtained with density functional theory in conjunction with various exchange-correlation functionals also shows that DFT remains unsuited for quantitative insights into kinetic rate constants. Analysis of the computed structures, bond orders, and free energy profiles demonstrates that the reaction steps involved in the removal of hydrogen atoms by OH radicals satisfy Hammond's principle. Computations of branching ratios also show that these reactions do not exhibit a particularly pronounced site-selectivity.

  14. UV + V UV double-resonance studies of autoionizing Rydberg states of the hydroxyl radical

    NASA Astrophysics Data System (ADS)

    Green, Amy M.; Liu, Fang; Lester, Marsha I.

    2016-05-01

    The hydroxyl radical (OH) is a key oxidant in atmospheric and combustion chemistry. Recently, a sensitive and state-selective ionization method has been developed for detection of the OH radical that utilizes UV excitation on the A2Σ+-X2Π transition followed by fixed 118 nm vacuum ultraviolet (VUV) radiation to access autoionizing Rydberg states [J. M. Beames et al., J. Chem. Phys. 134, 241102 (2011)]. The present study uses tunable VUV radiation generated by four-wave mixing to examine the origin of the enhanced ionization efficiency observed for OH radicals prepared in specific A2Σ+ intermediate levels. The enhancement is shown to arise from resonant excitation to distinct rotational and fine structure levels of two newly identified 2Π Rydberg states with an A3Π cationic core and a 3d electron followed by ionization. Spectroscopic constants are derived and effects due to uncoupling of the Rydberg electron are revealed for the OH 2Π Rydberg states. The linewidths indicate a Rydberg state lifetime due to autoionization on the order of a picosecond.

  15. Hydroxyl radical in/on illuminated polar snow: formation rates, lifetimes, and steady-state concentrations

    NASA Astrophysics Data System (ADS)

    Chen, Zeyuan; Chu, Liang; Galbavy, Edward S.; Ram, Keren; Anastasio, Cort

    2016-08-01

    While the hydroxyl radical (OH) in the snowpack is likely a dominant oxidant for organic species and bromide, little is known about the kinetics or steady-state concentrations of OH on/in snow and ice. Here we measure the formation rate, lifetime, and concentration of OH for illuminated polar snow samples studied in the laboratory and in the field. Laboratory studies show that OH kinetics and steady-state concentrations are essentially the same for a given sample studied as ice and liquid; this is in contrast to other photooxidants, which show a concentration enhancement in ice relative to solution as a result of kinetic differences in the two phases. The average production rate of OH in samples studied at Summit, Greenland, is 5 times lower than the average measured in the laboratory, while the average OH lifetime determined in the field is 5 times higher than in the laboratory. These differences indicate that the polar snows we studied in the laboratory are affected by contamination, despite significant efforts to prevent this; our results suggest similar contamination may be a widespread problem in laboratory studies of ice chemistry. Steady-state concentrations of OH in clean snow studied in the field at Summit, Greenland, range from (0.8 to 3) × 10-15 M, comparable to values reported for midlatitude cloud and fog drops, rain, and deliquesced marine particles, even though impurity concentrations in the snow samples are much lower. Partitioning of firn air OH to the snow grains will approximately double the steady-state concentration of snow-grain hydroxyl radical, leading to an average [OH] in near-surface, summer Summit snow of approximately 4 × 10-15 M. At this concentration, the OH-mediated lifetimes of organics and bromide in Summit snow grains are approximately 3 days and 7 h, respectively, suggesting that hydroxyl radical is a major

  16. Production of hydroxyl radicals from Fe-containing fine particles in Guangzhou, China

    NASA Astrophysics Data System (ADS)

    Ma, Shexia; Ren, Ke; Liu, Xiaowen; Chen, Laiguo; Li, Mei; Li, Xiaoying; Yang, Jian; Huang, Bo; Zheng, Mei; Xu, Zhencheng

    2015-12-01

    Reactive oxygen species (ROS) production from ambient fine particles has been correlated with the soluble transition metal content of PM2.5, which also has clear association with particle-mediated cardiopulmonary toxicity. Hydroxyl radical (rad OH) is the most harmful ROS species through chemical reactions of redox-active particle components. Atmospheric Fe, as the dominant species of the transition metals in the atmosphere, is associated with rad OH generation in ambient particle extracts. Our results revealed that Fe-containing particles (18,730 in total number) contributed approximately 3.7% on average to all detected particles throughout the summer and winter sampling period in Guangzhou, which was clustered into four distinct particle classes, including Fe-rich, Metal-rich, NaK-rich and Dust-rich. Fe-rich class was the dominant one with a fraction of 61%, followed by Dust-rich (14%), Metal-rich (13%). and NaK-rich (12%). The iron oxide was enriched in the Fe-rich class. rad OH generation induced by Fe-containing fine particles collected in Guangzhou (GZ) was quantified in a surrogate lung fluid (SLF), and it was found that Fe-containing fine particles were generally much reactive in generating rad OH in the presence of four antioxidants (200 μM ascorbate, 300 μM citrate, 100 μM reduced L-glutathione, and 100 μM uric acid). The annual average rad OH amount produced in our samples was 132.98 ± 27.43 nmol rad OH mg-1 PM2.5. rad OH production had a clear seasonal pattern with higher amount in summer and lower in winter. By measuring the amount of total and SLF-soluble metal in our PM2.5 samples using ICP-MS, we found that ROS activities were associated with the ionizable Fe through Fenton type reactions in the Guangzhou PM2.5. Expected burdens of PM2.5 derived rad OH in human lung lining fluid suggests that typical daily particulate matter exposure in Guangzhou is already a concern, and it could produce much higher levels of rad OH, leading to higher

  17. Effect of adenosine A(2A) receptor antagonists on L-DOPA-induced hydroxyl radical formation in rat striatum.

    PubMed

    Gołembiowska, Krystyna; Dziubina, Anna; Kowalska, Magdalena; Kamińska, Katarzyna

    2009-02-01

    A(2A) adenosine receptor antagonists have been proposed as a new therapy for Parkinson's disease (PD). Since oxidative stress plays an important role in the pathogenesis of PD, we studied the effect of the selective A(2A) adenosine receptor antagonists 8-(3-chlorostyryl)caffeine (CSC) and 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) on L: -3,4-dihydroxyphenylalanine (L: -DOPA)-induced hydroxyl radical generation using in vivo microdialysis in the striatum of freely moving rats. L: -DOPA (100 mg/kg; in the presence of benserazide, 50 mg/kg) given acutely or repeatedly for 14 days generated a high level of hydroxyl radicals, measured by HPLC with electrochemical detection, as the product of their reaction with p-hydroxybenzoic acid (PBA). CSC (1 mg/kg) and ZM 241385 (3 mg/kg) decreased haloperidol (0.5 mg/kg)-induced catalepsy, while at low doses of 0.1 and 0.3 mg/kg, respectively, they did not display an effect. CSC (1 and 5 mg/kg) and ZM 241385 (3 and 9 mg/kg) given acutely, or CSC (1 mg/kg) and ZM 241385 (3 mg/kg) given repeatedly, increased the production of hydroxyl radicals in dialysates from rat striatum. Both acute and repeated administration of CSC (0.1 and 1 mg/kg) and ZM 241385 (3 mg/kg) decreased L: -DOPA-induced generation of hydroxyl radicals. However, a high single dose of either CSC (5 mg/kg) and ZM 241385 (9 mg/kg) markedly potentiated the effect of L: -DOPA on hydroxyl radical production. The increase in hydroxyl radical production by acute and chronic injection of CSC and ZM 241385 may be related to the increased release of dopamine (DA) and its metabolism in striatal dialysates. Similarly, increased DA release following a single high dose of CSC or ZM 241385 appears to be responsible for augmentation of L: -DOPA-induced hydroxyl radical formation. Conversely, the inhibition of L: -DOPA-induced production of hydroxyl radical by single and repeated low doses of CSC or repeated low doses of ZM

  18. Formation of long-lived hydroxyl free radical adducts of proline and hydroxyproline in a Fenton reaction.

    PubMed

    Floyd, R A; Nagy, I

    1984-10-09

    Proline and hydroxyproline when exposed to the hydroxyl free radical generating system of ADP-Fe(II)-H2O2 yielded long-lived free radicals. An analysis of the electron paramagnetic resonance spectra of the long-lived hydroxyl free radical adducts of proline and hydroxyproline is consistent with a free electron on a nitroxyl group interacting with the nitrogen atom as well as with three separate protons. In the case of proline, nitroxide formation was observed under the influence of tert-butyl-hydroperoxide, giving a similar EPR spectrum (Lin, J.S., Tom, T.C. and Olcott, H.S. (1974) J. Agr. Food Chem. 22, 526-528); however, the hydroxyl free radical adduct of hydroxyproline has not been described yet. In the case of the proline nitroxide radical, two of the three protons involved interact with the free electron equivalently. The coupling constants for the hydroxyl free radical adduct of proline are AN = 1.58 mT, AH1 beta = AH2 beta = 2.13 mT, AH3 beta = 1.77 mT and for hydroxyproline are AN = 1.54 mT, AH1 beta = 2.56 mT, AH2 beta = 2.03 and AH3 beta = 1.51. The data are consistent with the amine nitrogen of proline and hydroxyproline being oxidized to a nitroxyl group and the free electron of the nitroxyl interacting with the beta-protons of these amino acid hydroxyl free radical adducts.

  19. Inhibition of Fe(2+)- and Fe(3+)- induced hydroxyl radical production by the iron-chelating drug deferiprone.

    PubMed

    Timoshnikov, V A; Kobzeva, T V; Polyakov, N E; Kontoghiorghes, G J

    2015-01-01

    Deferiprone (L1) is an effective iron-chelating drug that is widely used for the treatment of iron-overload diseases. It is known that in aqueous solutions Fe(2+) and Fe(3+) ions can produce hydroxyl radicals via Fenton and photo-Fenton reactions. Although previous studies with Fe(2+) have reported ferroxidase activity by L1 followed by the formation of Fe(3+) chelate complexes and potential inhibition of Fenton reaction, no detailed data are available on the molecular antioxidant mechanisms involved. Similarly, in vitro studies have also shown that L1-Fe(3+) complexes exhibit intense absorption bands up to 800nm and might be potential sources of phototoxicity. In this study we have applied an EPR spin trapping technique to answer two questions: (1) does L1 inhibit the Fenton reaction catalyzed by Fe(2+) and Fe(3+) ions and (2) does UV-Vis irradiation of the L1-Fe(3+) complex result in the formation of reactive oxygen species. PBN and TMIO spin traps were used for detection of oxygen free radicals, and TEMP was used to trap singlet oxygen if it was formed via energy transfer from L1 in the triplet excited state. It was demonstrated that irradiation of Fe(3+) aqua complexes by UV and visible light in the presence of spin traps results in the appearance of an EPR signal of the OH spin adduct (TMIO-OH, a(N)=14.15G, a(H)=16.25G; PBN-OH, a(N)=16.0G, a(H)=2.7G). The presence of L1 completely inhibited the OH radical production. The mechanism of OH spin adduct formation was confirmed by the detection of methyl radicals in the presence of dimethyl sulfoxide. No formation of singlet oxygen was detected under irradiation of L1 or its iron complexes. Furthermore, the interaction of L1 with Fe(2+) ions completely inhibited hydroxyl radical production in the presence of hydrogen peroxide. These findings confirm an antioxidant targeting potential of L1 in diseases related to oxidative damage.

  20. Water-catalyzed gas-phase reaction of formic acid with hydroxyl radical: A computational investigation

    NASA Astrophysics Data System (ADS)

    Luo, Yi; Maeda, Satoshi; Ohno, Koichi

    2009-02-01

    The reaction of formic acid with hydroxyl radical, which is considered to be relevant to atmospheric chemistry, has been extensively studied. A water-catalyzed process of this reaction is computationally studied here for the first time. The scaled hypersphere search method was used for global exploration of pre-reaction complexes. Calculations were performed at high level of theory, such as CCSD(T)/cc-pVTZ//B3LYP/6-311+G(2df, 2p) and CCSD(T)/cc-pVTZ//MP2/aug-cc-pVDZ. It is found that the water-catalyzed process of this reaction is more kinetically favorable than its non-catalytic process. Such catalytic process may also be of interest for atmospheric chemistry, like the non-catalytic one.

  1. Determination of hydroxyl radicals with salicylic acid in aqueous nitrate and nitrite solutions.

    PubMed

    Yang, Xi; Zhan, Man-jun; Kong, Ling-ren; Wang, Lian-sheng

    2004-01-01

    The qualitative and quantitative analyses of reactive oxygen species are essential to determine their steady-state concentration and related reaction mechanisms in environmental aquatic systems. In this study, salicylic acid was employed as an innovative molecular probe of hydroxyl radical(OH) generated in aqueous nitrate and nitrite solutions through photochemical reactions. Kinetic studies showed that the steady-state concentrations of OH in aqueous NO3- (10 mmol/L, pH = 5) and NO2- (10 mmol/L, pH = 5) solutions under ultraviolet irradiation were at a same magnitude, 10(-15) mol/L. Apparent quantum yields of OH at 313 nm were measured as 0.011 and 0.07 for NO3- and NO2- respectively, all comparable to the results of previous studies.

  2. Contribution of hydroxyl radical to radiosensitization: a study of DNA damage

    SciTech Connect

    Skov, K.A.

    1984-09-01

    Using the radioprotector dimethylsulfoxide, DMSO, as a scavenger of hydroxyl radicals, the proportions of DNA damage caused by OH were determined in mammalian cells irradiated in hypoxia with or without the radiosensitizers misonidazole and TAN or in air. Yields of both single-strand breaks (SSB) and base/sugar damage (MLS for Micrococcus luteus sensitive sites) were measured for each situation. Most of the damage enhanced by the sensitizers was found to be OH dependent, for both MLS and SSB classes of damage. The sensitizer enhancement ratios in the presence of scavenger and the degree of protection afforded by the scavenger determined for total (MSL + SSB) damage agree well with those derived from corresponding survival experiments.

  3. Basis for sensitive and selective time-delayed luminescence detection of hydroxyl radical by lanthanide complexes.

    PubMed

    Peterson, Katie L; Margherio, Maximilian J; Doan, Phi; Wilke, Kyle T; Pierre, Valérie C

    2013-08-19

    Molecular probes for the detection of hydroxyl radical (HO•) by time-delayed luminescence spectroscopy directly in water at neutral pH with high sensitivity and selectivity are presented. The bimolecular probes consist of a lanthanide complex with open coordination sites and a reactive pre-antenna composed of an aromatic acid or amide; the latter binds to and sensitizes terbium emission upon hydroxylation by HO•. These probes exhibit long luminescence lifetimes compatible with time-delayed measurements that remove interfering background fluorescence from the sample. Six different reactive pre-antenna (benzoate, benzamide, isophthalate, isophthalamide, trimesate, and trimesamide) and two different terbium complexes [Tb-(1,4,7,10-tetraazacyclododecane-1,4,7-tris(acetic acid)) (Tb-DO3A) and Tb-(1,4,7,10-tetraazacyclododecane-1,7-bis(acetic acid)) (Tb-DO2A)] were evaluated. Of these the trimesamide/Tb-DO3A system enables the most sensitive detection of HO• with an about 1000-fold increase in metal-centered time-delayed emission upon hydroxylation of the pre-antenna to 2-hydroxytrimesamide. Excellent selectivity for both the trimesamide/Tb-DO3A and trimesate/Tb-DO3A systems over other reactive oxygen and nitrogen species are observed. Notably, the increase in metal-centered luminescence intensity is not associated with a decrease in the hydration number (q) of Tb-DO3A, suggesting that the antenna is interacting with the lanthanide via a second sphere coordination environment or that coordination by the antenna occurs by displacement of one or more of the carboxylate arms of DO3A. Formation of a weak ternary complex Tb-DO3A•hydroxytrimesamide was confirmed by temperature-dependent titration and a decrease in K(app) with increasing temperature.

  4. Hydroxyl and Hydroperoxy Radical Chemistry during the MCMA-2006 Field Campaign: Measurement and Model Comparison

    NASA Astrophysics Data System (ADS)

    Dusanter, S.; Vimal, D.; Stevens, P. S.; Volkamer, R.; Molina, L. T.

    2007-12-01

    The Mexico City Metropolitan Area (MCMA) field campaign, held in March 2006, was a unique opportunity to collect data in one of the most polluted megacities in the world. Such environments exhibit a complex oxidation chemistry involving a strong coupling between odd hydrogen radicals (HOX=OH+HO2) and nitrogen oxides species (NOX=NO+NO2). High levels of volatile organic compounds (VOCs) and NOX control the HOX budget and lead to elevated tropospheric ozone formation. The HOX-NOX coupling can be investigated by comparing measured and model-predicted HOx concentrations. Atmospheric HOX concentrations were measured by the Indiana University laser-induced fluorescence instrument and data were collected at the Instituto Mexicano del Petroleo between 14 and 31 March. Measured hydroxyl radical (OH) concentrations are comparable to that measured in less polluted urban environments and suggest that the OH concentrations are highly buffered under high NOX conditions. In contrast, hydroperoxy radical (HO2) concentrations are more sensitive to the NOX levels and are highly variable between different urban sites. Enhanced levels of OH and HO2 radicals were observed on several days between 9h30-11h00 AM and suggest an additional HOX source for the morning hours and/or a fast HOX cycling under the high NOX conditions of the MCMA. A preliminary investigation of the HOX chemistry occurring in the MCMA urban atmosphere was performed using a photochemical box model based on the Regional Atmospheric Chemistry Mechanism (RACM). Model comparisons will be presented and the agreement between measured and predicted HOX concentrations will be discussed.

  5. Sensitive electrochemical measurement of hydroxyl radical generation induced by the xanthine-xanthine oxidase system.

    PubMed

    Tatsumi, Hirosuke; Tsuchiya, Yui; Sakamoto, Koichi

    2014-12-15

    A sensitive electrochemical measurement system for hydroxyl radical (OH) was developed using enzyme-catalyzed signal amplification. In the presence of 2,6-xylenol as a trapping agent, glucose as a substrate, and pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) as a catalyst, the amperometric signal of the trapping adduct 2,6-dimethylhydroquinone (DMHQ) produced by the hydroxylation of 2,6-xylenol was able to be amplified and detected sensitively. The limit of detection (signal/noise [S/N]=3) for DMHQ was 1 nM. There was no significant interference from urate and other oxidizable compounds in the reaction mixture at the applied potential of 0V versus Ag/AgCl. This method was employed to observe the OH generation induced by the xanthine-xanthine oxidase (XO) system. The reaction rates of the DMHQ production induced from the xanthine-XO system in the presence and absence of various Fe(III) complexes and proteins were compared. Those with a free coordination site on the Fe atom effectively enhanced the OH generation.

  6. Degradation of artificial sweetener saccharin in aqueous medium by electrochemically generated hydroxyl radicals.

    PubMed

    Lin, Heng; Wu, Jie; Oturan, Nihal; Zhang, Hui; Oturan, Mehmet A

    2016-03-01

    The removal of artificial sweetener saccharin (SAC) in aqueous solution by electrochemical advanced oxidation using electro-Fenton process was performed. Experiments were carried out in an undivided cylindrical glass cell with a carbon-felt cathode and a Pt or boron-doped diamond (BDD) anode. The removal of SAC by electrochemically generated hydroxyl radicals followed pseudo-first-order kinetics with both Pt and BDD anode. The absolute rate constant of the SAC hydroxylation reaction was determined for the first time using the competition kinetic method and found to be (1.85 ± 0.01) × 10(9) M(-1) s(-1). The comparative study of TOC removal efficiency during electro-Fenton treatment indicated a higher mineralization rate with BDD than Pt anode. The identification and evolution of short-chain carboxylic acids and inorganic ions formed during oxidation process were monitored by ion-exchange chromatography and ion chromatography, respectively. The assessment of toxicity of SAC and/or its reaction by-products during treatment was performed using Microtox® method based on the Vibrio fischeri bacteria luminescence inhibition. Results showed that the process was able to efficiently detoxify the treated solution.

  7. Degradation mechanism of cyanobacterial toxin cylindrospermopsin by hydroxyl radicals in homogeneous UV/H₂O₂ process.

    PubMed

    He, Xuexiang; Zhang, Geshan; de la Cruz, Armah A; O'Shea, Kevin E; Dionysiou, Dionysios D

    2014-04-15

    The degradation of cylindrospermopsin (CYN), a widely distributed and highly toxic cyanobacterial toxin (cyanotoxin), remains poorly elucidated. In this study, the mechanism of CYN destruction by UV-254 nm/H2O2 advanced oxidation process (AOP) was investigated by mass spectrometry. Various byproducts identified indicated three common reaction pathways: hydroxyl addition (+16 Da), alcoholic oxidation or dehydrogenation (-2 Da), and elimination of sulfate (-80 Da). The initiation of the degradation was observed at the hydroxymethyl uracil and tricyclic guanidine groups; uracil moiety cleavage/fragmentation and further ring-opening of the alkaloid were also noted at an extended reaction time or higher UV fluence. The degradation rates of CYN decreased and less byproducts (species) were detected using natural water matrices; however, CYN was effectively eliminated under extended UV irradiation. This study demonstrates the efficiency of CYN degradation and provides a better understanding of the mechanism of CYN degradation by hydroxyl radical, a reactive oxygen species that can be generated by most AOPs and is present in natural water environment.

  8. Supercharging by m-NBA Improves ETD-Based Quantification of Hydroxyl Radical Protein Footprinting.

    PubMed

    Li, Xiaoyan; Li, Zixuan; Xie, Boer; Sharp, Joshua S

    2015-08-01

    Hydroxyl radical protein footprinting (HRPF) is an MS-based technique for analyzing protein structure based on measuring the oxidation of amino acid side chains by hydroxyl radicals diffusing in solution. Spatial resolution of HRPF is limited by the smallest portion of the protein for which oxidation amounts can be accurately quantitated. Previous work has shown electron transfer dissociation (ETD) to be the most reliable method for quantifying the amount of oxidation of each amino acid side chain in a mixture of peptide oxidation isomers, but efficient ETD requires high peptide charge states, which limits its applicability for HRPF. Supercharging reagents have been used to enhance peptide charge state for ETD analysis, but previous work has shown supercharging reagents to enhance charge state differently for different peptides sequences; it is currently unknown if different oxidation isomers will experience different charge enhancement effects. Here, we report the effect of m-nitrobenzyl alcohol (m-NBA) on the ETD-based quantification of peptide oxidation. The addition of m-NBA to both a defined mixture of synthetic isomeric oxidized peptides and Robo-1 protein subjected to HRPF increased the abundance of higher charge state ions, improving our ability to perform efficient ETD of the mixture. No differences in the reported quantitation by ETD were noted in the presence or absence of m-NBA, indicating that all oxidation isomers were charge-enhanced to a similar extent. These results indicate the utility of m-NBA for residue-level quantification of peptide oxidation in HRPF and other applications.

  9. Supercharging by m-NBA Improves ETD-Based Quantification of Hydroxyl Radical Protein Footprinting

    NASA Astrophysics Data System (ADS)

    Li, Xiaoyan; Li, Zixuan; Xie, Boer; Sharp, Joshua S.

    2015-08-01

    Hydroxyl radical protein footprinting (HRPF) is an MS-based technique for analyzing protein structure based on measuring the oxidation of amino acid side chains by hydroxyl radicals diffusing in solution. Spatial resolution of HRPF is limited by the smallest portion of the protein for which oxidation amounts can be accurately quantitated. Previous work has shown electron transfer dissociation (ETD) to be the most reliable method for quantifying the amount of oxidation of each amino acid side chain in a mixture of peptide oxidation isomers, but efficient ETD requires high peptide charge states, which limits its applicability for HRPF. Supercharging reagents have been used to enhance peptide charge state for ETD analysis, but previous work has shown supercharging reagents to enhance charge state differently for different peptides sequences; it is currently unknown if different oxidation isomers will experience different charge enhancement effects. Here, we report the effect of m-nitrobenzyl alcohol ( m-NBA) on the ETD-based quantification of peptide oxidation. The addition of m-NBA to both a defined mixture of synthetic isomeric oxidized peptides and Robo-1 protein subjected to HRPF increased the abundance of higher charge state ions, improving our ability to perform efficient ETD of the mixture. No differences in the reported quantitation by ETD were noted in the presence or absence of m-NBA, indicating that all oxidation isomers were charge-enhanced to a similar extent. These results indicate the utility of m-NBA for residue-level quantification of peptide oxidation in HRPF and other applications.

  10. Source-dependent variation in hydroxyl radical production by airborne particulate matter

    SciTech Connect

    Marjan Alaghmand; Neil V. Blough

    2007-04-01

    Epidemiological studies suggest exposure to airborne particles is responsible for a wide range of adverse health effects, potentially arising from particle-induced oxidative stress. A highly sensitive fluorescence method was employed to measure the production of hydroxyl radical by a broad range of particle types including urban dust, diesel particulate matter, coal fly ash, kaolinite, and silica. Little or no production of OH was observed in the absence of an added electron donor or H{sub 2}O{sub 2}. In the presence of a biological electron donor (NADPH, 3 mM), the rate of OH production (R{sub OH}) for 3 mg/mL of these particles varied from 23 nM s{sup -1} for diesel particulate matter (SRM 2975) to 0.20 nM s{sup -1} for coal fly ash (SRM 2689). No detectable OH was produced by kaolinite or silica. Hydroxyl radical formation was eliminated under anaerobic conditions and in the presence of catalase, indicating that O{sub 2} and H{sub 2}O{sub 2} are required for its generation. Partial inhibition of OH formation by superoxide dismutase (SOD) was also observed in some cases, suggesting that superoxide is also involved. The metal chelator deferoxamine mesylate (DFX) in most cases suppressed OH formation, but diethylenetriaminepentaacetic acid (DTPA) generally enhanced it, implicating metal ion reactions in OH generation as well. The dependence of R{sub OH} on NADPH concentration further implicates particle surface reactions in OH formation. To the authors' knowledge, these measurements provide the first quantitative estimate of ROH for a broad range of particle types. 49 refs., 6 figs., 1 tab.

  11. High structural resolution hydroxyl radical protein footprinting reveals an extended Robo1-heparin binding interface.

    PubMed

    Li, Zixuan; Moniz, Heather; Wang, Shuo; Ramiah, Annapoorani; Zhang, Fuming; Moremen, Kelley W; Linhardt, Robert J; Sharp, Joshua S

    2015-04-24

    Interaction of transmembrane receptors of the Robo family and the secreted protein Slit provides important signals in the development of the central nervous system and regulation of axonal midline crossing. Heparan sulfate, a sulfated linear polysaccharide modified in a complex variety of ways, serves as an essential co-receptor in Slit-Robo signaling. Previous studies have shown that closely related heparin octasaccharides bind to Drosophila Robo directly, and surface plasmon resonance analysis revealed that Robo1 binds more tightly to full-length unfractionated heparin. For the first time, we utilized electron transfer dissociation-based high spatial resolution hydroxyl radical protein footprinting to identify two separate binding sites for heparin interaction with Robo1: one binding site at the previously identified site for heparin dp8 and a second binding site at the N terminus of Robo1 that is disordered in the x-ray crystal structure. Mutagenesis of the identified N-terminal binding site exhibited a decrease in binding affinity as measured by surface plasmon resonance and heparin affinity chromatography. Footprinting also indicated that heparin binding induces a minor change in the conformation and/or dynamics of the Ig2 domain, but no major conformational changes were detected. These results indicate a second low affinity binding site in the Robo-Slit complex as well as suggesting the role of the Ig2 domain of Robo1 in heparin-mediated signal transduction. This study also marks the first use of electron transfer dissociation-based high spatial resolution hydroxyl radical protein footprinting, which shows great utility for the characterization of protein-carbohydrate complexes.

  12. High Structural Resolution Hydroxyl Radical Protein Footprinting Reveals an Extended Robo1-Heparin Binding Interface*

    PubMed Central

    Li, Zixuan; Moniz, Heather; Wang, Shuo; Ramiah, Annapoorani; Zhang, Fuming; Moremen, Kelley W.; Linhardt, Robert J.; Sharp, Joshua S.

    2015-01-01

    Interaction of transmembrane receptors of the Robo family and the secreted protein Slit provides important signals in the development of the central nervous system and regulation of axonal midline crossing. Heparan sulfate, a sulfated linear polysaccharide modified in a complex variety of ways, serves as an essential co-receptor in Slit-Robo signaling. Previous studies have shown that closely related heparin octasaccharides bind to Drosophila Robo directly, and surface plasmon resonance analysis revealed that Robo1 binds more tightly to full-length unfractionated heparin. For the first time, we utilized electron transfer dissociation-based high spatial resolution hydroxyl radical protein footprinting to identify two separate binding sites for heparin interaction with Robo1: one binding site at the previously identified site for heparin dp8 and a second binding site at the N terminus of Robo1 that is disordered in the x-ray crystal structure. Mutagenesis of the identified N-terminal binding site exhibited a decrease in binding affinity as measured by surface plasmon resonance and heparin affinity chromatography. Footprinting also indicated that heparin binding induces a minor change in the conformation and/or dynamics of the Ig2 domain, but no major conformational changes were detected. These results indicate a second low affinity binding site in the Robo-Slit complex as well as suggesting the role of the Ig2 domain of Robo1 in heparin-mediated signal transduction. This study also marks the first use of electron transfer dissociation-based high spatial resolution hydroxyl radical protein footprinting, which shows great utility for the characterization of protein-carbohydrate complexes. PMID:25752613

  13. Imidazole Metalloporphyrins as Photosensitizers for Photodynamic Therapy: Role of Molecular Charge, Central Metal and Hydroxyl Radical Production

    PubMed Central

    Mroz, Pawel; Bhaumik, Jayeeta; Dogutan, Dilek K.; Aly, Zarmeneh; Kamal, Zahra; Khalid, Laiqua; Kee, Hooi Ling; Bocian, David F.; Holten, Dewey; Lindsey, Jonathan S.; Hamblin, Michael R.

    2009-01-01

    SUMMARY The in vitro photodynamic therapy activity of four imidazole-substituted metalloporphyrins has been studied using human (HeLa) and mouse (CT26) cancer cell lines: an anionic Zn porphyrin and a homologous series of three cationic Zn, Pd or InCl porphyrins. A dramatic difference in phototoxicity was found: Pd cationic > InCl cationic > Zn cationic > Zn anionic. HeLa cells were more susceptible than CT26 cells. Induction of apoptosis was demonstrated using a fluorescent caspase assay. The anionic Zn porphyrin localized in lysosomes while the cationic Zn porphyrin localized in lysosomes and mitochondria, as assessed by fluorescence microscopy. Studies using fluorescent probes suggested that the cationic Pd porphyrin produced more hydroxyl radicals as the reactive oxygen species. Thus, the cationic Pd porphyrin has high potential as a photosensitizer and gives insights into characteristics for improved molecular designs. PMID:19346065

  14. Inhibition of membrane lipid peroxidation by a radical scavenging mechanism: a novel function for hydroxyl-containing ionophores.

    PubMed

    Grijalba, M T; Andrade, P B; Meinicke, A R; Castilho, R F; Vercesi, A E; Schreier, S

    1998-03-01

    In the present study we show that K+/H+ hydroxyl-containing ionophores lasalocid-A (LAS) and nigericin (NIG) in the nanomolar concentration range, inhibit Fe2+-citrate and 2,2'-azobis(2-amidinopropane) dihydrochloride (ABAP)-induced lipid peroxidation in intact rat liver mitochondria and in egg phosphatidylcholine (PC) liposomes containing negatively charged lipids--dicetyl phosphate (DCP) or cardiolipin (CL)--and KCl as the osmotic support. In addition, monensin (MON), a hydroxyl-containing ionophore with higher affinity for Na+ than for K+, promotes a similar effect when NaCl is the osmotic support. The protective effect of the ionophores is not observed when the osmolyte is sucrose. Lipid peroxidation was evidenced by mitochondrial swelling, antimycin A-insensitive O2 consumption, formation of thiobarbituric acid-reactive substances (TBARS), conjugated dienes, and electron paramagnetic resonance (EPR) spectra of an incorporated lipid spin probe. A time-dependent decay of spin label EPR signal is observed as a consequence of lipid peroxidation induced by both inductor systems in liposomes. Nitroxide destruction is inhibited by butylated hydroxytoluene, a known antioxidant, and by the hydroxyl-containing ionophores. In contrast, valinomycin (VAL), which does not possess alcoholic groups, does not display this protective effect. Effective order parameters (Seff), determined from the spectra of an incorporated spin label are larger in the presence of salt and display a small increase upon addition of the ionophores, as a result of the increase of counter ion concentration at the negatively charged bilayer surface. This condition leads to increased formation of the ion-ionophore complex, the membrane binding (uncharged) species. The membrane-incorporated complex is the active species in the lipid peroxidation inhibiting process. Studies in aqueous solution (in the absence of membranes) showed that NIG and LAS, but not VAL, decrease the Fe2+-citrate-induced production

  15. Studies of hydroxyl radical and hydroperoxyl radical in the region of the arctic winter tropopause

    NASA Astrophysics Data System (ADS)

    Simpas, James Bernard B.

    This study is based on in situ measurements made on the NASA DC-8 during the SAGE III Ozone Loss and Validation Experiment/Third European Stratospheric Experiment on Ozone (SOLVE/THESEO) campaign which was conducted in the 1999-2000 Arctic winter (November, 1999 to April, 2000). The DC-8’s extensive coverage of the arctic winter tropopause region afforded the opportunity to probe more deeply into the unique chemistry of the upper troposphere/lower stratosphere (UTLS). Central to this analysis are the measurements of OH, HO2⊂ (collectively called HOx⊂), and halogen oxides that play a crucial role in the chemistry of this region. We discuss the modified configuration of the Penn State Airborne Tropospheric Hydrogen Oxides Sensor (ATHOS) in order to accommodate the University of Colorado ClO/BrO instrument, the salient points of the measurement profiles that were obtained by this unique instrument, the shifts of these profiles in the presence of cirrus clouds that may indicate heterogeneous processing/activation of halogen reservoir species, and the projected impact of the abundance of these species on the local chemical ozone budget in the region.

  16. [The production of hydroxyl radical in HRP-NADH-H2O/O2 systems and its application in chlorobenzene removal].

    PubMed

    Li, Hai-tao; Li, Yu-ping; Cao, Hong-bin; Li, Xin-gang; Xue, Zhan-qiang

    2010-11-01

    The mechanism of radical generation in HRP-NADH-O2/H2O2 systems and state-change of horseradish peroxidase (HRP) was investigated by using ESR and UV measurements, and the novel enzyme-coenzymatic systems were performed to degrade chlorobenzene as a non-phenolic persistent organic pollutants. The UV results showed that compound III was produced from HRP oxidized by hydrogen peroxide with the catalysis of NADH, which would generate hydroxyl radical. The ESR results demonstrated the production of *OH and O2-. in enzyme-coenzymatic system in the presence of O2 or H2O2 with DMPO and POBN as spin-trappers, respectively. In HRP-NADH-H2O2 system, compound III was the main state of HRP in the initial 10 min, and then converted to HRP with generating hydroxyl radical; and after the addition of oxygen, the production of hydroxyl radical was promoted rapidly, as 4 times as that of the system in absence of oxygen. The addition of SOD(Zn-Cu) decreased the production of hydroxyl radical significantly, resulting from that SOD eliminated O2 reduction to O2-. by NADH and then inhibited *OH formation. The results showed that NADH could improve by about 20% enzyme activity of HRP for phenol removal. The removal of chlorobenzene with HRP-NADH-H2O2 and HRP-NADH-H2O2-O2 systems reached 24.6% and 48.2%, respectively, which was much higher than that with traditional enzymatic system (1.42%), showing a promising prospect in proposal

  17. Hydroxyl radical scavenging assay of phenolics and flavonoids with a modified cupric reducing antioxidant capacity (CUPRAC) method using catalase for hydrogen peroxide degradation.

    PubMed

    Ozyürek, Mustafa; Bektaşoğlu, Burcu; Güçlü, Kubilay; Apak, Reşat

    2008-06-02

    Hydroxyl radicals (OH) generated in the human body may play an important role in tissue injury at sites of inflammation in oxidative stress-originated diseases. As a more convenient, efficient, and less costly alternative to HPLC/electrochemical detection techniques and to the nonspecific, low-yield deoxyribose (TBARS) test, we used a salicylate probe for detecting OH generated by the reaction of iron(II)-EDTA complex with H(2)O(2). The produced hydroxyl radicals attack both the salicylate probe and the hydroxyl radical scavengers that are incubated in solution for 10 min. Added radical scavengers compete with salicylate for the OH produced, and diminish chromophore formation from Cu(II)-neocuproine. At the end of the incubation period, the reaction was stopped by adding catalase. With the aid of this reaction, a kinetic approach was adopted to assess the hydroxyl radical scavenging properties of polyphenolics, flavonoids and other compounds (e.g., ascorbic acid, glucose, mannitol). A second-order rate constant for the reaction of the scavenger with OH could be deduced from the inhibition of colour formation due to the salicylate probe. In addition to phenolics and flavonoids, five kinds of herbs were evaluated for their OH scavenging activity using the developed method. The modified CUPRAC (cupric ion reducing antioxidant capacity) assay proved to be efficient for ascorbic acid, gallic acid and chlorogenic acid, for which the deoxyribose assay test is basically nonresponsive. An important contribution of this developed assay is the inhibition of the Fenton reaction with catalase degradation of hydrogen peroxide so that the remaining H(2)O(2) would neither give a CUPRAC absorbance nor involve in redox cycling of phenolic antioxidants, enabling the rapid assay of polyphenolics.

  18. Hydroxyl radical induced oxidation of theophylline in water: a kinetic and mechanistic study.

    PubMed

    Sunil Paul, M M; Aravind, U K; Pramod, G; Saha, A; Aravindakumar, C T

    2014-08-14

    Oxidative destruction and mineralization of emerging organic pollutants by hydroxyl radicals (˙OH) is a well established area of research. The possibility of generating hazardous by-products in the case of ˙OH reaction demands extensive investigations on the degradation mechanism. A combination of pulse radiolysis and steady state photolysis (H2O2/UV photolysis) followed by high resolution mass spectrometric (HRMS) analysis have been employed to explicate the kinetic and mechanistic features of the destruction of theophylline, a model pharmaceutical compound and an identified pollutant, by ˙OH in the present study. The oxidative destruction of this molecule, for intermediate product studies, was initially achieved by H2O2/UV photolysis. The transient absorption spectrum corresponding to the reaction of ˙OH with theophylline at pH 6, primarily caused by the generation of (T8-OH)˙, was characterised by an absorption band at 330 nm (k2 = (8.22 ± 0.03) × 10(9) dm(3) mol(-1) s(-1)). A significantly different spectrum (λmax: 340 nm) was observed at highly alkaline pH (10.2) due to the deprotonation of this radical (pKa∼ 10.0). Specific one electron oxidants such as sulphate radical anions (SO4˙(-)) and azide radicals (N3˙) produce the deprotonated form (T(-H)˙) of the radical cation (T˙(+)) of theophylline (pKa 3.1) with k2 values of (7.51 ± 0.04) × 10(9) dm(3) mol(-1) s(-1) and (7.61 ± 0.02) × 10(9) dm(3) mol(-1) s(-1) respectively. Conversely, oxide radicals (O˙(-)) react with theophylline via a hydrogen abstraction protocol with a rather slow k2 value of (1.95 ± 0.02) × 10(9) dm(3) mol(-1) s(-1). The transient spectral studies were complemented by the end product profile acquired by HRMS analysis. Various transformation products of theophylline induced by ˙OH were identified by this technique which include derivatives of uric acids (i, iv & v) and xanthines (ii, iii & vi). Further breakdown of the early formed product due to ˙OH attack leads to

  19. Quantitative aspects of ESR and spin trapping of hydroxyl radicals and hydrogen atoms in gamma-irradiated aqueous solutions.

    PubMed

    Carmichael, A J; Makino, K; Riesz, P

    1984-11-01

    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.

  20. Cupric ion reducing antioxidant capacity assay for antioxidants in human serum and for hydroxyl radical scavengers.

    PubMed

    Apak, Reşat; Güçlü, Kubilay; Ozyürek, Mustafa; Bektaşoğlu, Burcu; Bener, Mustafa

    2010-01-01

    , for which the FRAP (ferric reducing antioxidant potency) test is basically nonresponsive. The additivity of absorbances of all the tested antioxidants confirmed that antioxidants in the CUPRAC test do not chemically interact among each other so as to cause an intensification or quenching of the theoretically expected absorbance, and that a total antioxidant capacity (TAC) assay of serum is possible. As a distinct advantage over other electron-transfer based assays (e.g., Folin, FRAP, ABTS, DPPH), CUPRAC is superior in regard to its realistic pH close to the physiological pH, favorable redox potential, accessibility and stability of reagents, and applicability to lipophilic antioxidants as well as hydrophilic ones. The CUPRAC procedure can also assay hydroxyl radicals, being the most reactive oxygen species (ROS). As a more convenient, efficient, and less costly alternative to HPLC/electrochemical detection techniques and to the nonspecific, low-yield TBARS test, we use p-aminobenzoate, 2,4- and 3,5-dimethoxybenzoate probes for detecting hydroxyl radicals generated from an equivalent mixture of [Fe(II)+EDTA] with hydrogen peroxide. The produced hydroxyl radicals attack both the probe and the water-soluble antioxidants in 37 degrees C-incubated solutions for 2 h. The CUPRAC absorbance of the ethylacetate extract due to the reduction of Cu(II)-neocuproine reagent by the hydroxylated probe decreases in the presence of (.)OH scavengers, the difference being proportional to the scavenging ability of the tested compound. The developed method is less lengthy, more specific, and of a higher yield than the classical TBARS assay.

  1. Quantification of photoelectrogenerated hydroxyl radical on TiO2 by surface interrogation scanning electrochemical microscopy.

    PubMed

    Zigah, Dodzi; Rodríguez-López, Joaquín; Bard, Allen J

    2012-10-05

    The surface interrogation mode of scanning electrochemical microscopy (SI-SECM) was used for the detection and quantification of adsorbed hydroxyl radical ˙OH((ads)) generated photoelectrochemically at the surface of a nanostructured TiO(2) substrate electrode. In this transient technique, a SECM tip is used to generate in situ a titrant from a reversible redox pair that reacts with the adsorbed species at the substrate. This reaction produces an SECM feedback response from which the amount of adsorbate and its decay kinetics can be obtained. The redox pair IrCl(6)(2-/3-) offered a reactive, selective and stable surface interrogation agent under the strongly oxidizing conditions of the photoelectrochemical cell. A typical ˙OH((ads)) saturation coverage of 338 μC cm(-2) was found in our nanostructured samples by its reduction with the electrogenerated IrCl(6)(3-). The decay kinetics of ˙OH((ads)) by dimerization to produce H(2)O(2) were studied through the time dependence of the SI-SECM signal and the surface dimerization rate constant was found to be ~k(OH) = 2.2 × 10(3) mol(-1) m(2) s(-1). A radical scavenger, such as methanol, competitively consumes ˙OH((ads)) and yields a shorter SI-SECM transient, where a pseudo-first order rate analysis at 2 M methanol yields a decay constant of k'(MeOH) ~ 1 s(-1).

  2. Photochemical Formation of Hydroxyl Radical in Red-Soil-Polluted Seawater in Okinawa, Japan -Potential Impacts on Marine Organisms

    NASA Astrophysics Data System (ADS)

    Arakaki, T.; Hamdun, A. M.; Okada, K.; Kuroki, Y.; Ikota, H.; Fujimura, H.; Oomori, T.

    2004-12-01

    Development of pineapple farmlands and construction of recreational facilities caused runoff of red soil into coastal ocean (locally termed as red-soil-pollution) in the north of Okinawa Island, Japan. In an attempt to understand the impacts of red soil on oxidizing power of the seawater, we studied formation of hydroxyl radical (OH radical), the most potent oxidant in the environment, in red-soil-polluted seawaters, using 313 nm monochromatic light. Photo-formation rates of OH radical showed a good correlation with dissolved iron concentrations (R = 0.98). The major source of OH radical was found to be the Fenton reaction (a reaction between Fe(II) and HOOH). The un-filtered red-soil-polluted seawater samples exhibited faster OH radical formation rates than the filtered samples, suggesting that iron-bearing red soil particles enhanced formation of OH radical.

  3. POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZOFURANS: GAS-PHASE HYDROXYL RADICAL REACTIONS AND RELATED ATMOSPHERIC REMOVAL. (R825377)

    EPA Science Inventory

    Gas-phase reactions with the hydroxyl radical (OH) are
    expected to be an important removal pathway of polychlorinated dibenzo-p-dioxins and dibenzofurans
    (PCDD/F)
    in the atmosphere. Our laboratory recently developed
    a system to measure the rate constants of ...

  4. Lunasin peptide purified from Solanum nigrum L. protects DNA from oxidative damage by suppressing the generation of hydroxyl radical via blocking fenton reaction.

    PubMed

    Jeong, Jin Boo; De Lumen, Ben O; Jeong, Hyung Jin

    2010-07-01

    Oxidative DNA damage is the most critical factor implicated in carcinogenesis and other disorders. However, the protective effects of lunasin against oxidative DNA damage have not yet reported. In this study, we report here the protective effect of lunasin purified from Solanum nigrum L. against oxidative DNA. Lunasin protected DNA from the oxidative damage induced by Fe(2+) ion and hydroxyl radical. To better understand the mechanism for the protective effect of lunasin against DNA damage, the abilities to chelate Fe(2+), scavenge the generated hydroxyl radical and block the generation of hydroxyl radical were evaluated. Although it did not scavenge generated hydroxyl radical, lunasin blocked the generation of hydroxyl radical by chelating Fe(2+) ion. We conclude that lunasin protects DNA from oxidation by blocking fenton reaction between Fe(2+) and H(2)O(2) by chelating Fe(2+) and that consumption of lunasin may play an important role in the chemoprevention for the oxidative carcinogenesis.

  5. DNA damage produced by exposure of supercoiled plasmid DNA to high- and low-LET ionizing radiation: Effects of hydroxyl radical quenchers. DNA breakage, neutrons, OH radicals

    SciTech Connect

    Peak, J.G.; Ito, T.; Peak, M.J.; Robb, F.T.

    1994-08-01

    A supercoiled plasmid of 7300 base pairs was isolated and exposed in an aqueous environment to {sup 60}Co {gamma} rays and JANUS 0.85 MeV fission-spectrum neutrons. Dose responses for the production of single-strand breaks (SSBs), double-strand breaks (DSBs) and alkali-labile sites (ALSs) were compared with computations made from the conversion of the supercoil to its relaxed and linear forms. The relative biological effectiveness (RBE) for production of SSBs and DSBs was similar to that previously measured in the cellular environment. The RBE for destruction of genetic transforming activity of M13 viral DNA followed that for DNA damage. This is in contrast to the situation for biological effects such as lethality, mutagenesis, and cellular transformation measured in mammalian cells, where the RBE values are reversed. The role of hydroxyl (OH) radical in DNA damage induction by neutrons was investigated by exposure of plasmid in the presence of known quenchers of this species. Of four quenchers tested, all were able to reduce the yields of both SSBs and DSBs. These findings are consistent with a model for SSB and DSB induction by high linear energy transfer that involves OH radical mediation.

  6. Reduction of Hexavalent Chromium by Human Cytochrome b5: Generation of Hydroxyl Radical and Superoxide

    PubMed Central

    Borthiry, Griselda R.; Antholine, William E.; Kalyanaraman, B.; Myers, Judith M.; Myers, Charles R.

    2007-01-01

    The reduction of hexavalent chromium, Cr(VI), can generate reactive Cr intermediates and various types of oxidative stress. The potential role of human microsomal enzymes in free radical generation was examined using reconstituted proteoliposomes (PLs) containing purified cytochrome b5 and NADPH:P450 reductase. Under aerobic conditions, the PLs reduced Cr(VI) to Cr(V) which was confirmed by ESR using isotopically pure 53Cr(VI). When 5-Diethoxyphos-phoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) was included as a spin trap, a very prominent signal for the hydroxyl radical (HO•) adduct was observed as well as a smaller signal for the superoxide (O2•−) adduct. These adducts were observed even at very low Cr(VI) concentrations (10 μM). NADPH, Cr(VI), O2 and the PLs were all required for significant HO• generation. Superoxide dismutase eliminated the O2• − adduct and resulted in a 30% increase in the HO• adduct. Catalase largely diminished the HO• adduct signal indicating its dependence on H2O2. Some sources of catalase were found to have Cr(VI)-reducing contaminants which could confound results, but a source of catalase free of these contaminants was used for these studies. Exogenous H2O2 was not needed, indicating that it was generated by the PLs. Adding exogenous H2O2, however, did increase the amount of DEPMPO/HO• adduct. The inclusion of formate yielded the carbon dioxide radical adduct of DEPMPO, and experiments with dimethylsulfoxide (DMSO) plus the spin trap α-phenyl-N-tert-butylnitrone (PBN) yielded the methoxy and methyl radical adducts of PBN, confirming the generation of HO•. Quantification of the various species over time was consistent with a stoichiometric excess of HO• relative to the net amount of Cr(VI) reduced. This also represents the first demonstration of a role for cytochrome b5 in the generation of HO•. Overall, the simultaneous generation of Cr(V) and H2O2 by the PLs and the resulting generation of HO• at low Cr

  7. A Novel High-Throughput Approach to Measure Hydroxyl Radicals Induced by Airborne Particulate Matter

    PubMed Central

    Son, Yeongkwon; Mishin, Vladimir; Welsh, William; Lu, Shou-En; Laskin, Jeffrey D.; Kipen, Howard; Meng, Qingyu

    2015-01-01

    Oxidative stress is one of the key mechanisms linking ambient particulate matter (PM) exposure with various adverse health effects. The oxidative potential of PM has been used to characterize the ability of PM induced oxidative stress. Hydroxyl radical (•OH) is the most destructive radical produced by PM. However, there is currently no high-throughput approach which can rapidly measure PM-induced •OH for a large number of samples with an automated system. This study evaluated four existing molecular probes (disodium terephthalate, 3′-p-(aminophenyl)fluorescein, coumarin-3-carboxylic acid, and sodium benzoate) for their applicability to measure •OH induced by PM in a high-throughput cell-free system using fluorescence techniques, based on both our experiments and on an assessment of the physicochemical properties of the probes reported in the literature. Disodium terephthalate (TPT) was the most applicable molecular probe to measure •OH induced by PM, due to its high solubility, high stability of the corresponding fluorescent product (i.e., 2-hydroxyterephthalic acid), high yield compared with the other molecular probes, and stable fluorescence intensity in a wide range of pH environments. TPT was applied in a high-throughput format to measure PM (NIST 1648a)-induced •OH, in phosphate buffered saline. The formed fluorescent product was measured at designated time points up to 2 h. The fluorescent product of TPT had a detection limit of 17.59 nM. The soluble fraction of PM contributed approximately 76.9% of the •OH induced by total PM, and the soluble metal ions of PM contributed 57.4% of the overall •OH formation. This study provides a promising cost-effective high-throughput method to measure •OH induced by PM on a routine basis. PMID:26516887

  8. Catechol oxidation by ozone and hydroxyl radicals at the air-water interface.

    PubMed

    Pillar, Elizabeth A; Camm, Robert C; Guzman, Marcelo I

    2014-12-16

    Anthropogenic emissions of aromatic hydrocarbons promptly react with hydroxyl radicals undergoing oxidation to form phenols and polyphenols (e.g., catechol) typically identified in the complex mixture of humic-like substances (HULIS). Because further processing of polyphenols in secondary organic aerosols (SOA) can continue mediated by a mechanism of ozonolysis at interfaces, a better understanding about how these reactions proceed at the air-water interface is needed. This work shows how catechol, a molecular probe of the oxygenated aromatic hydrocarbons present in SOA, can contribute interfacial reactive species that enhance the production of HULIS under atmospheric conditions. Reactive semiquinone radicals are quickly produced upon the encounter of 40 ppbv-6.0 ppmv O3(g) with microdroplets containing [catechol] = 1-150 μM. While the previous pathway results in the instantaneous formation of mono- and polyhydroxylated aromatic rings (PHA) and chromophoric mono- and polyhydroxylated quinones (PHQ), a different channel produces oxo- and dicarboxylic acids of low molecular weight (LMW). The cleavage of catechol occurs at the 1,2 carbon-carbon bond at the air-water interface through the formation of (1) an ozonide intermediate, (2) a hydroperoxide, and (3) cis,cis-muconic acid. However, variable [catechol] and [O3(g)] can affect the ratio of the primary products (cis,cis-muconic acid and trihydroxybenzenes) and higher order products observed (PHA, PHQ, and LMW oxo- and dicarboxylic acids). Secondary processing is confirmed by mass spectrometry, showing the production of crotonic, maleinaldehydic, maleic, glyoxylic, and oxalic acids. The proposed pathway can contribute precursors to aqueous SOA (AqSOA) formation, converting aromatic hydrocarbons into polyfunctional species widely found in tropospheric aerosols with light-absorbing brown carbon.

  9. Insight into the free-radical-scavenging mechanism of hydroxyl-substituent Schiff bases in the free-radical-induced hemolysis of erythrocytes.

    PubMed

    Tang, You-Zhi; Liu, Zai-Qun

    2007-01-01

    This work aimed to explore the mechanism by which hydroxyl-substituent Schiff bases scavenge free-radicals. Thus, four Schiff bases, that is benzylidene aniline (BAN), 2-(phenyliminomethyl)phenol (BAH), 4-benzimidoylphenol (PBH) and 2-benzimidoylphenol (OBH), were applied to protect human erythrocytes against 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced hemolysis. The results revealed that the --OH attached to the ortho-position of methylene in Schiff base scavenges 1.46 radicals per molecule, the --OH attached to the para-position of the N atom scavenges 2.94 radicals and the --OH attached to the ortho-position of the N atom scavenges 3.63 radicals. In addition, four Schiff bases were used together with some familiar antioxidants, such as 6-hydroxyl-2,5,7,8-tetramethyl chroman-2-carboxylic acid (Trolox), L-ascorbic acid (VC), alpha-tocopherol (TOH) and L-ascorbyl-6-laurate (VC-12) in AAPH-induced hemolysis of erythrocytes. It was found that, except for BAN+VC-12, BAH + VC-12, OBH + VC-12 and PBH+TOH, all the other combinations protected erythrocytes more perfectly than when used individually. This result demonstrated that a promotive protection existed between Schiff base and other antioxidants and this improved their ability to scavenge free-radicals. Finally, IC(50) values of the aforementioned Schiff bases together with 2-((o-hydroxylphenylimino) methyl)phenol (OSAP) and 2-((p-hydroxylphenylimino)methyl)phenol (PSAP) were determined by reaction with two radical species, that is, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) radical (ABTS(+.)) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH). The results implied that the molecular framework of a Schiff base and an --OH attached to the ortho-position of methylene were apt to reduce radicals, but the --OH attached to the aniline ring in a Schiff base was prone to scavenge radicals directly.

  10. Numerical analysis of quantitative measurement of hydroxyl radical concentration using laser-induced fluorescence in flame

    NASA Astrophysics Data System (ADS)

    Shuang, Chen; Tie, Su; Yao-Bang, Zheng; Li, Chen; Ting-Xu, Liu; Ren-Bing, Li; Fu-Rong, Yang

    2016-06-01

    The aim of the present work is to quantitatively measure the hydroxyl radical concentration by using LIF (laser-induced fluorescence) in flame. The detailed physical models of spectral absorption lineshape broadening, collisional transition and quenching at elevated pressure are built. The fine energy level structure of the OH molecule is illustrated to understand the process with laser-induced fluorescence emission and others in the case without radiation, which include collisional quenching, rotational energy transfer (RET), and vibrational energy transfer (VET). Based on these, some numerical results are achieved by simulations in order to evaluate the fluorescence yield at elevated pressure. These results are useful for understanding the real physical processes in OH-LIF technique and finding a way to calibrate the signal for quantitative measurement of OH concentration in a practical combustor. Project supported by the National Natural Science Foundation of China (Grant No. 11272338) and the Fund from the Science and Technology on Scramjet Key Laboratory, China (Grant No. STSKFKT2013004).

  11. Formation of fluorescent polydopamine dots from hydroxyl radical-induced degradation of polydopamine nanoparticles.

    PubMed

    Lin, Jia-Hui; Yu, Cheng-Ju; Yang, Ya-Chun; Tseng, Wei-Lung

    2015-06-21

    This study describes the synthesis of fluorescent polydopamine dots (PDs) through hydroxyl radical-induced degradation of polydopamine nanoparticles. The decomposition of polydopamine nanoparticles to fluorescent PDs was confirmed using transmission electron microscopy and dark-field microscopy. The analysis of PDs by using laser desorption/ionization time-of-flight mass spectrometry revealed that the PDs consisted of dopamine, 5,6-dihydroxyindole, and trihydroxyindole units. Oligomerization and self-assembly of these units produced a broad adsorption band, resulting in an excitation-wavelength-dependent emission behavior. The maximal fluorescence of PDs appeared at 440 nm with a quantum yield of 1.2%. The coordination between the catechol groups of PDs and ferric ions (Fe(3+)) quenched the fluorescence of PDs; the limit of detection at a signal-to-noise ratio of 3 for Fe(3+) was determined to be 0.3 μM. The presence of pyrophosphate switched on the fluorescence of the PD-Fe(3+) complexes. Compared to the other reported methods for sensing Fe(3+), PDs provided simple, low-cost, and reusable detection of Fe(3+).

  12. In vivo cell wall loosening by hydroxyl radicals during cress seed germination and elongation growth.

    PubMed

    Müller, Kerstin; Linkies, Ada; Vreeburg, Robert A M; Fry, Stephen C; Krieger-Liszkay, Anja; Leubner-Metzger, Gerhard

    2009-08-01

    Loosening of cell walls is an important developmental process in key stages of the plant life cycle, including seed germination, elongation growth, and fruit ripening. Here, we report direct in vivo evidence for hydroxyl radical ((*)OH)-mediated cell wall loosening during plant seed germination and seedling growth. We used electron paramagnetic resonance spectroscopy to show that (*)OH is generated in the cell wall during radicle elongation and weakening of the endosperm of cress (Lepidium sativum; Brassicaceae) seeds. Endosperm weakening precedes radicle emergence, as demonstrated by direct biomechanical measurements. By (3)H fingerprinting, we showed that wall polysaccharides are oxidized in vivo by the developmentally regulated action of apoplastic (*)OH in radicles and endosperm caps: the production and action of (*)OH increased during endosperm weakening and radicle elongation and were inhibited by the germination-inhibiting hormone abscisic acid. Both effects were reversed by gibberellin. Distinct and tissue-specific target sites of (*)OH attack on polysaccharides were evident. In vivo (*)OH attack on cell wall polysaccharides were evident not only in germinating seeds but also in elongating maize (Zea mays; Poaceae) seedling coleoptiles. We conclude that plant cell wall loosening by (*)OH is a controlled action of this type of reactive oxygen species.

  13. Estimating hydroxyl radical photochemical formation rates in natural waters during long-term laboratory irradiation experiments.

    PubMed

    Sun, Luni; Chen, Hongmei; Abdulla, Hussain A; Mopper, Kenneth

    2014-04-01

    In this study it was observed that, during long-term irradiations (>1 day) of natural waters, the methods for measuring hydroxyl radical (˙OH) formation rates based upon sequentially determined cumulative concentrations of photoproducts from probes significantly underestimate actual ˙OH formation rates. Performing a correction using the photodegradation rates of the probe products improves the ˙OH estimation for short term irradiations (<1 day), but not long term irradiations. Only the 'instantaneous' formation rates, which were obtained by adding probes to aliquots at each time point and irradiating these sub-samples for a short time (≤2 h), were found appropriate for accurately estimating ˙OH photochemical formation rates during long-term laboratory irradiation experiments. Our results also showed that in iron- and dissolved organic matter (DOM)-rich water samples, ˙OH appears to be mainly produced from the Fenton reaction initially, but subsequently from other sources possibly from DOM photoreactions. Pathways of ˙OH formation in long-term irradiations in relation to H2O2 and iron concentrations are discussed.

  14. Hydroxyl radical formation upon oxidation of reduced humic acids by oxygen in the dark.

    PubMed

    Page, Sarah E; Sander, Michael; Arnold, William A; McNeill, Kristopher

    2012-02-07

    Humic acids (HAs) accept and donate electrons in many biogeochemical redox reactions at oxic/anoxic interfaces. The products of oxidation of reduced HAs by O(2) are unknown but are expected to yield reactive oxygen species, potentially including hydroxyl radical (·OH). To quantify the formation of ·OH upon oxidation of reduced HAs by O(2), three HAs were reduced electrochemically to well-defined redox states and were subsequently oxidized by O(2) in the presence of the ·OH probe terephthalate. The formation of ·OH upon oxidation increased with increasing extent of HA reduction. The yield of ·OH ranged from 42 to 160 mmol per mole of electrons donated by the reduced HA. The intermediacy of hydrogen peroxide (H(2)O(2)) in the formation of ·OH was supported by enhancement of ·OH formation upon addition of exogenous H(2)O(2) sources and by the suppression of ·OH formation upon addition of catalase as a quencher of endogenous H(2)O(2). The formation of ·OH in the dark during oxidation of reduced HA represents a previously unknown source of ·OH formation at oxic/anoxic interfaces and may affect the biogeochemical and pollutant redox dynamics at these interfaces.

  15. Dark formation of hydroxyl radical in Arctic soil and surface waters.

    PubMed

    Page, Sarah E; Kling, George W; Sander, Michael; Harrold, Katherine H; Logan, J Robert; McNeill, Kristopher; Cory, Rose M

    2013-11-19

    Hydroxyl radical (•OH) is a highly reactive and unselective oxidant in atmospheric and aquatic systems. Current understanding limits the role of DOM-produced •OH as an oxidant in carbon cycling mainly to sunlit environments where •OH is produced photochemically, but a recent laboratory study proposed a sunlight-independent pathway in which •OH forms during oxidation of reduced aquatic dissolved organic matter (DOM) and iron. Here we demonstrate this non-photochemical pathway for •OH formation in natural aquatic environments. Across a gradient from dry upland to wet lowland habitats, •OH formation rates increase with increasing concentrations of DOM and reduced iron, with highest •OH formation predicted at oxic-anoxic boundaries in soil and surface waters. Comparison of measured vs expected electron release from reduced moieties suggests that both DOM and iron contribute to •OH formation. At landscape scales, abiotic DOM oxidation by this dark •OH pathway may be as important to carbon cycling as bacterial oxidation of DOM in arctic surface waters.

  16. Sources of hydroxyl radical in headwater streams from nitrogen-saturated forest.

    PubMed

    Chiwa, Masaaki; Higashi, Naoko; Otsuki, Kyoichi; Kodama, Hiroki; Miyajima, Tohru; Takeda, Kazuhiko; Sakugawa, Hiroshi

    2015-01-01

    Hydroxyl radical (HO) photoformation rate (RHO) was determined in headwater stream samples from nitrogen (N)-saturated forests, (1) to quantify the sources of HO in headwater streams and (2) to evaluate the nitrate NO3(-)-induced enhancement of HO formation in stream water caused by N saturation in forested watersheds. Stream water fulvic acid extracted from the forested watersheds was used to quantify the contribution of dissolved organic matter (DOM) to RHO. The results showed that almost all (97%; 81-109%) RHO sources in our headwater stream samples were quantitatively elucidated; the photolysis of NO3(-) (55%; 34-75%), nitrite [N(III)] (2%; 0.5-5.2%), and DOM-derived HO formation, from which photo-Fenton reactions (18%; 12-26%) and the direct photolysis of fluorescent dissolved organic matter (FDOM) (22%; 10-40%), was successfully separated. FDOM, which accounted for 53% (24-96%) of DOM in total organic carbon bases, was responsible for HO formation in our headwater streams. High NO3(-) leaching caused by N saturation in forested watersheds increased RHO in the headwaters, indicating that N-saturated forest could significantly change photoinduced and biogeochemical processes via enhanced HO formation in downstream water.

  17. Rate coefficients of hydroxyl radical reactions with pesticide molecules and related compounds: A review

    NASA Astrophysics Data System (ADS)

    Wojnárovits, László; Takács, Erzsébet

    2014-03-01

    Rate coefficients published in the literature on hydroxyl radical reactions with pesticides and related compounds are discussed together with the experimental methods and the basic reaction mechanisms. Recommendations are made for the most probable values. Most of the molecules whose rate coefficients are discussed have aromatic ring: their rate coefficients are in the range of 2×109-1×1010 mol-1 dm3 s-1. The rate coefficients show some variation with the electron withdrawing-donating nature of the substituent on the ring. The rate coefficients for triazine pesticides (simazine, atrazine, prometon) are all around 2.5×109 mol-1 dm3 s-1. The values do not show variation with the substituent on the s-triazine ring. The rate coefficients for the non-aromatic molecules which have C=C double bonds or several C-H bonds may also be above 1×109 mol-1 dm3 s-1. However, the values for molecules without C=C double bonds or several C-H bonds are in the 1×107-1×109 mol-1 dm3 s-1 range.

  18. Ultrasonic application to boost hydroxyl radical formation during Fenton oxidation and release organic matter from sludge.

    PubMed

    Gong, Changxiu; Jiang, Jianguo; Li, De'an; Tian, Sicong

    2015-06-12

    We examined the effects of ultrasound and Fenton reagent on ultrasonic coupling Fenton oxidation (U+F) pre-treatment processes for the disintegration of wastewater treatment plant sludge. The results demonstrated that U+F treatment could significantly increase soluble chemical oxygen demand (SCOD), total organic carbon (TOC), and extracellular polymeric substances (EPS) concentrations in sludge supernatant. This method was more effective than ultrasonic (U) or Fenton oxidation (F) treatment alone. U+F treatment increased the release of SCOD by 2.1- and 1.4-fold compared with U and F alone, respectively. U+F treatment increased the release of EPS by 1.2-fold compared with U alone. After U+F treatment, sludge showed a considerably finer particle size and looser microstructure based on fluorescence microscopy, and the concentration of hydroxyl radicals (OH•) increased from 0.26 mM by F treatment to 0.43 mM by U+F treatment based on fluorescence spectrophotometer. This demonstrated that U+F treatment improves the release of organic matter from sludge.

  19. HOCl-dependent singlet oxygen and hydroxyl radical generation modulate and induce apoptosis of malignant cells.

    PubMed

    Bauer, Georg

    2013-09-01

    The lack of extracellular superoxide anion production by non-transformed cells prevents H2O2/peroxidase-mediated HOCl synthesis by these cells, as well as apoptosis induction by exogenous HOCl. In contrast, transformed cells generate extracellular superoxide anions and HOCl, and die by apoptosis after HOCl/superoxide-dependent hydroxyl radical generation at their membrane. Tumor cells prevent HOCl synthesis through expression of membrane-associated catalase, but their extracellular superoxide anions readily react with exogenous HOCl. The interaction between HOCl and H2O2 causes singlet oxygen generation that inactivates superoxide dismutase (SOD) on the surface of the tumor cells and thus enhances HOCl-mediated apoptosis through an increase in free superoxide anions. Higher concentrations of singlet oxygen inactivate membrane-associated catalase and thus lead to partial inhibition of apoptosis induction by exogenous HOCl, due to consumption of HOCl by H2O2. The data presented here show a complex, but coherent picture of interactions between defined reactive oxygen species and protective enzymes on the surface of tumor cells.

  20. Ultrasonic application to boost hydroxyl radical formation during Fenton oxidation and release organic matter from sludge

    NASA Astrophysics Data System (ADS)

    Gong, Changxiu; Jiang, Jianguo; Li, De'An; Tian, Sicong

    2015-06-01

    We examined the effects of ultrasound and Fenton reagent on ultrasonic coupling Fenton oxidation (U+F) pre-treatment processes for the disintegration of wastewater treatment plant sludge. The results demonstrated that U+F treatment could significantly increase soluble chemical oxygen demand (SCOD), total organic carbon (TOC), and extracellular polymeric substances (EPS) concentrations in sludge supernatant. This method was more effective than ultrasonic (U) or Fenton oxidation (F) treatment alone. U+F treatment increased the release of SCOD by 2.1- and 1.4-fold compared with U and F alone, respectively. U+F treatment increased the release of EPS by 1.2-fold compared with U alone. After U+F treatment, sludge showed a considerably finer particle size and looser microstructure based on fluorescence microscopy, and the concentration of hydroxyl radicals (OH•) increased from 0.26 mM by F treatment to 0.43 mM by U+F treatment based on fluorescence spectrophotometer. This demonstrated that U+F treatment improves the release of organic matter from sludge.

  1. Mechanistic Study of the Validity of Using Hydroxyl Radical Probes To Characterize Electrochemical Advanced Oxidation Processes.

    PubMed

    Jing, Yin; Chaplin, Brian P

    2017-02-21

    The detection of hydroxyl radicals (OH(•)) is typically accomplished by using reactive probe molecules, but prior studies have not thoroughly investigated the suitability of these probes for use in electrochemical advanced oxidation processes (EAOPs), due to the neglect of alternative reaction mechanisms. In this study, we investigated the suitability of four OH(•) probes (coumarin, p-chlorobenzoic acid, terephthalic acid, and p-benzoquinone) for use in EAOPs. Experimental results indicated that both coumarin and p-chlorobenzoic acid are oxidized via direct electron transfer reactions, while p-benzoquinone and terephthalic acid are not. Coumarin oxidation to form the OH(•) adduct product 7-hydroxycoumarin was found at anodic potentials lower than that necessary for OH(•) formation. Density functional theory (DFT) simulations found a thermodynamically favorable and non-OH(•) mediated pathway for 7-hydroxycoumarin formation, which is activationless at anodic potentials > 2.10 V/SHE. DFT simulations also provided estimates of E° values for a series of OH(•) probe compounds, which agreed with voltammetry results. Results from this study indicated that terephthalic acid is the most appropriate OH(•) probe compound for the characterization of electrochemical and catalytic systems.

  2. Experimental Determination of the Electric Dipole Moment Function of the X Pi-2 Hydroxyl Radical

    NASA Technical Reports Server (NTRS)

    Chackerian, C., Jr.; Goorvitch, D.; Abrams, M. C.; Davis, S. P.; Benidar, A.; Farrenq, R.; Guelachvili, G.; Strawa, Anthony W. (Technical Monitor)

    1995-01-01

    Laboratory infrared emission spectra of X 2piOH obtained with the Solar McMath FTS and the U. Paris (Orsay) FTS are used in an inversion procedure to experimentally determine the electric dipole moment function (EDMF) of the hydroxyl radical. The spectra produced at Kitt Peak show vibrational levels up to v = 10 and rotational lines in the range, -25.5 less than or equal to m less than or equal to 12.5. The following vibrational quantum number ranges were observed: for DELTA v = -1, v prime = 1 - 9, for DELTA v = -2, v prime = 2 - 10, and for DELTA v = - 3, v prime = 6 - 10. The spectra produced at Orsay show DELTA v = -1, with v prime = 1 - 4 and -22.5 less than or equal to m less than or equal to 9.5 as well as DELTA v = 0, with v prime= 1 - 3, and 9.5 less than or equal to m less than or equal to 25.5. The OH rovibrational wavefunctions used in the inversion procedure were calculated using a procedure which reproduces observed rotational constants with a high level of accuracy. Comparisons of our EDMF are made with previous experimental and theoretical work.

  3. Fingerprinting of hydroxyl radical-attacked polysaccharides by N-isopropyl-2-aminoacridone labelling

    PubMed Central

    Vreeburg, Robert A. M.; Airianah, Othman B.; Fry, Stephen C.

    2014-01-01

    Hydroxyl radicals (•OH) cause non-enzymic scission of polysaccharides in diverse biological systems. Such reactions can be detrimental (e.g. causing rheumatic and arthritic diseases in mammals) or beneficial (e.g. promoting the softening of ripening fruit, and biomass saccharification). Here we present a method for documenting •OH action, based on fluorescent labelling of the oxo groups that are introduced as glycosulose residues when •OH attacks polysaccharides. The method was tested on several polysaccharides, especially pectin, after treatment with Fenton reagents. 2-Aminoacridone plus cyanoborohydride reductively aminated the oxo groups in treated polysaccharides; the product was then reacted with acetone plus cyanoborohydride, forming a stable tertiary amine with the carbohydrate linked to N-isopropyl-2-aminoacridone (pAMAC). Digestion of labelled pectin with ‘Driselase’ yielded several fluorescent products which on electrophoresis and HPLC provided a useful ‘fingerprint’ indicating •OH attack. The most diagnostic product was a disaccharide conjugate of the type pAMAC·UA-GalA (UA=unspecified uronic acid), whose UA-GalA bond was Driselase-resistant (product 2A). 2A was clearly distinguishable from GalA-GalA–pAMAC (disaccharide labelled at its reducing end), which was digestible to GalA–pAMAC. The methodology is applicable, with appropriate enzymes in place of Driselase, for detecting natural and artificial •OH attack in diverse plant, animal and microbial polysaccharides. PMID:25072268

  4. Hydroxyl radical mediates N epsilon-(carboxymethyl)lysine formation from Amadori product.

    PubMed

    Nagai, R; Ikeda, K; Higashi, T; Sano, H; Jinnouchi, Y; Araki, T; Horiuchi, S

    1997-05-08

    Recent studies demonstrated N epsilon-(carboxymethyl)lysine (CML) in several tissue proteins. Incubation of proteins with glucose leads through a Schiff base to Amadori products. Oxidative cleavage of Amadori products is considered as a major route to CML formation in vivo, whereas it is not known which reactive oxygen species (ROS) is involved. The present study is undertaken to identify such a ROS. We prepared heavily glycated human serum albumin (HSA) which contained a high level of Amadori products, but an undetectable level of CML. Incubation of glycated HSA with FeCl2, but not with H2O2, led to CML formation which was enhanced by H2O2, but inhibited by catalase or mannitol, whereas superoxide dismutase had no effect. Similar data were obtained by experiments using Boc-fructose-lysine as a model Amadori compound. These data indicate that hydroxyl radical generated by the reaction of Fe2+ with H2O2 mediates CML formation from Amadori compounds.

  5. Hydrogen peroxide release and hydroxyl radical formation in mixtures containing mineral fibres and human neutrophils.

    PubMed

    Leanderson, P; Tagesson, C

    1992-11-01

    The ability of different mineral fibres (rock wool, glass wool, ceramic fibres, chrysotile A, chrysotile B, amosite, crocidolite, antophyllite, erionite, and wollastonite) to stimulate hydrogen peroxide (H2O2) and hydroxyl radical (OH.) formation in mixtures containing human polymorphonuclear leucocytes (PMNLs) was investigated. In the presence of azide, all the fibres caused considerable H2O2 formation, and about twice as much H2O2 was found in mixtures with the natural fibres (asbestos, erionite, and wollastonite) than in mixtures with the manmade fibres (rock wool, glass wool, and ceramic fibres). In the presence of externally added iron, all the fibres were found to generate OH. and the natural fibres caused about three times more OH. formation than the manmade fibres. In the absence of external iron, there was less OH. formation; however, amosite, crocidolite, antophyllite, erionite, and wollastonite still generated considerable amounts of OH., also under circumstances in which only small amounts of OH. were produced in mixtures with the manmade fibres. These findings indicate that natural fibres generate more H2O2 and OH. than manmade fibres when incubated with PMNLs in the presence of external iron. They also suggest that the natural fibres, amosite, crocidolite, antophyllite, erionite, and wollastonite may act catalytically in the dissociation of H2O2 to OH. in the absence of external iron, whereas manmade fibres such as rock wool, glass wool, and ceramic fibres, do not seem to be able to generate OH. in the absence of external iron.

  6. Hydroxyl radicals in the tropical troposphere over the Suriname rainforest: airborne measurements

    NASA Astrophysics Data System (ADS)

    Martinez, M.; Harder, H.; Kubistin, D.; Rudolf, M.; Bozem, H.; Eerdekens, G.; Fischer, H.; Gurk, C.; Klüpfel, T.; Königstedt, R.; Parchatka, U.; Schiller, C. L.; Stickler, A.; Williams, J.; Lelieveld, J.

    2008-08-01

    Direct measurements of OH and HO2 over a tropical rainforest were made for the first time during the GABRIEL campaign in October 2005, deploying the custom-built HORUS instrument (HydrOxyl Radical measurement Unit based on fluorescence Spectroscopy), adapted to fly in a Learjet wingpod. Biogenic hydrocarbon emissions were expected to strongly reduce the OH and HO2 mixing ratios as the air is transported from the ocean over the forest. However, surprisingly high mixing ratios of both OH and HO2 were encountered in the boundary layer over the rainforest. The HORUS instrumentation and calibration methods are described in detail and the measurement results obtained are discussed. The extensive dataset collected during GABRIEL, including measurements of many other trace gases and photolysis frequencies, has been used to quantify the main sources and sinks of OH. Comparison of these measurement-derived formation and loss rates of OH indicates strong previously overlooked recycling of OH in the boundary layer over the tropical rainforest, occurring in chorus with isoprene emission.

  7. Hydroxyl radicals in the tropical troposphere over the Suriname rainforest: airborne measurements

    NASA Astrophysics Data System (ADS)

    Martinez, M.; Harder, H.; Kubistin, D.; Rudolf, M.; Bozem, H.; Eerdekens, G.; Fischer, H.; Klüpfel, T.; Gurk, C.; Königstedt, R.; Parchatka, U.; Schiller, C. L.; Stickler, A.; Williams, J.; Lelieveld, J.

    2010-04-01

    Direct measurements of OH and HO2 over a tropical rainforest were made for the first time during the GABRIEL campaign in October 2005, deploying the custom-built HORUS instrument (HydrOxyl Radical measurement Unit based on fluorescence Spectroscopy), adapted to fly in a Learjet wingpod. Biogenic hydrocarbon emissions were expected to strongly reduce the OH and HO2 mixing ratios as the air is transported from the ocean over the forest. However, surprisingly high mixing ratios of both OH and HO2 were encountered in the boundary layer over the rainforest. The HORUS instrumentation and calibration methods are described in detail and the measurement results obtained are discussed. The extensive dataset collected during GABRIEL, including measurements of many other trace gases and photolysis frequencies, has been used to quantify the main sources and sinks of OH. Comparison of these measurement-derived formation and loss rates of OH indicates strong previously overlooked recycling of OH in the boundary layer over the tropical rainforest, occurring in chorus with isoprene emission.

  8. Phytic acid suppresses 1-methyl-4-phenylpyridinium ion-induced hydroxyl radical generation in rat striatum.

    PubMed

    Obata, Toshio

    2003-07-18

    The present study examined the antioxidant effect of phytic acid on iron (II)-enhanced hydroxyl radical (*OH) generation induced by 1-methyl-4-phenylpyridinium ion (MPP(+)) in the extracellular fluid of rat striatum. Rats were anesthetized, and sodium salicylate in Ringer's solution (0.5 nmol/microl/min) was infused through a microdialysis probe to detect the generation of *OH as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. Phytic acid (100 microM) did not significantly decrease the levels of MPP(+)-induced *OH formation trapped as 2,3-DHBA. To confirm the generation of *OH by the Fenton-type reaction, iron (II) was infused through a microdialysis probe. Introduction of iron (II) (10 microM) enhanced MPP(+) induced *OH generation. However, phytic acid significantly suppressed iron (II)-enhanced *OH formation after MPP(+) treatment (n=6, P<0.05). These results suggest that the antiradical effect of phytic acid occurs by chelating iron required for the MPP(+)-enhanced *OH generation via the Fenton-type reaction.

  9. Ultrasonic application to boost hydroxyl radical formation during Fenton oxidation and release organic matter from sludge

    PubMed Central

    Gong, Changxiu; Jiang, Jianguo; Li, De’an; Tian, Sicong

    2015-01-01

    We examined the effects of ultrasound and Fenton reagent on ultrasonic coupling Fenton oxidation (U+F) pre-treatment processes for the disintegration of wastewater treatment plant sludge. The results demonstrated that U+F treatment could significantly increase soluble chemical oxygen demand (SCOD), total organic carbon (TOC), and extracellular polymeric substances (EPS) concentrations in sludge supernatant. This method was more effective than ultrasonic (U) or Fenton oxidation (F) treatment alone. U+F treatment increased the release of SCOD by 2.1- and 1.4-fold compared with U and F alone, respectively. U+F treatment increased the release of EPS by 1.2-fold compared with U alone. After U+F treatment, sludge showed a considerably finer particle size and looser microstructure based on fluorescence microscopy, and the concentration of hydroxyl radicals (OH•) increased from 0.26 mM by F treatment to 0.43 mM by U+F treatment based on fluorescence spectrophotometer. This demonstrated that U+F treatment improves the release of organic matter from sludge. PMID:26066562

  10. Hydrogen peroxide release and hydroxyl radical formation in mixtures containing mineral fibres and human neutrophils.

    PubMed Central

    Leanderson, P; Tagesson, C

    1992-01-01

    The ability of different mineral fibres (rock wool, glass wool, ceramic fibres, chrysotile A, chrysotile B, amosite, crocidolite, antophyllite, erionite, and wollastonite) to stimulate hydrogen peroxide (H2O2) and hydroxyl radical (OH.) formation in mixtures containing human polymorphonuclear leucocytes (PMNLs) was investigated. In the presence of azide, all the fibres caused considerable H2O2 formation, and about twice as much H2O2 was found in mixtures with the natural fibres (asbestos, erionite, and wollastonite) than in mixtures with the manmade fibres (rock wool, glass wool, and ceramic fibres). In the presence of externally added iron, all the fibres were found to generate OH. and the natural fibres caused about three times more OH. formation than the manmade fibres. In the absence of external iron, there was less OH. formation; however, amosite, crocidolite, antophyllite, erionite, and wollastonite still generated considerable amounts of OH., also under circumstances in which only small amounts of OH. were produced in mixtures with the manmade fibres. These findings indicate that natural fibres generate more H2O2 and OH. than manmade fibres when incubated with PMNLs in the presence of external iron. They also suggest that the natural fibres, amosite, crocidolite, antophyllite, erionite, and wollastonite may act catalytically in the dissociation of H2O2 to OH. in the absence of external iron, whereas manmade fibres such as rock wool, glass wool, and ceramic fibres, do not seem to be able to generate OH. in the absence of external iron. Images PMID:1334424

  11. Hyperfine structure of the hydroxyl free radical (OH) in electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Maeda, Kenji; Wall, Michael L.; Carr, Lincoln D.

    2015-05-01

    We investigate single-particle energy spectra of the hydroxyl free radical (OH) in the lowest electronic and rovibrational level under combined static electric and magnetic fields, as an example of heteronuclear polar diatomic molecules. In addition to the fine-structure interactions, the hyperfine interactions and centrifugal distortion effects are taken into account to yield the zero-field spectrum of the lowest 2Π3 / 2 manifold to an accuracy of less than 2kHz. We also examine level crossings and repulsions in the hyperfine structure induced by applied electric and magnetic fields. Compared to previous work, we found more than 10 percent reduction of the magnetic fields at level repulsions in the Zeeman spectrum subjected to a perpendicular electric field. In addition, we find new level repulsions, which we call Stark-induced hyperfine level repulsions, that require both an electric field and hyperfine structure. It is important to take into account hyperfine structure when we investigate physics of OH molecules at micro-Kelvin temperatures and below. This research was supported in part by AFOSR Grant No.FA9550-11-1-0224 and by the NSF under Grants PHY-1207881 and NSF PHY-1125915. We appreciate the Aspen Center for Physics, supported in part by the NSF Grant No.1066293, for hospitality.

  12. Generation of hydroxyl radicals from ambient fine particles in a surrogate lung fluid solution.

    PubMed

    Vidrio, Edgar; Phuah, Chin H; Dillner, Ann M; Anastasio, Cort

    2009-02-01

    While it has been hypothesized that the adverse health effects associated with ambient particulate matter (PM) are due to production of hydroxyl radical (*OH), few studies have quantified *OH production from PM. Here we report the amounts of *OH produced from ambient fine particles (PM2.5) collected in northern California and extracted in a cell-free surrogate lung fluid (SLF). On average, the extracted particles produced 470 nmol *OH mg(-1)-PM2.5 during our 15-month collection period. There was a clear seasonal pattern in the efficiency with which particles generated *OH, with highest production during spring and summer and lowest during winter. In addition, nighttime PM was typically more efficient than daytime PM at generating *OH. Transition metals played the dominant role in *OH production: on average (+/-sigma), the addition of desferoxamine (a chelator that prevents metals from forming *OH) to the SLF removed (90 +/- 5) % of *OH generation. Furthermore, based on the concentrations of Fe in the PM2.5 SLF extracts, and the measured yield of *OH as a function of Fe concentration, dissolved iron can account for the majority of *OH produced in most of our PM2.5 extracts.

  13. Generation of Hydroxyl Radicals from Ambient Fine Particles in a Surrogate Lung Fluid Solution

    PubMed Central

    Vidrio, Edgar; Phuah, Chin; Dillner, Ann M.; Anastasio, Cort

    2008-01-01

    While it has been hypothesized that the adverse health effects associated with ambient particulate matter (PM) are due to production of hydroxyl radical (·OH), few studies have quantified ·OH production from PM. Here we report the amounts of ·OH produced from ambient fine particles (PM2.5) collected in northern California and extracted in a cell-free surrogate lung fluid (SLF). On average, the extracted particles produced 470 nmol ·OH mg−1-PM2.5 during our 15-month collection period. There was a clear seasonal pattern in the efficiency with which particles generated ·OH, with highest production during spring and summer and lowest during winter. In addition, nighttime PM was typically more efficient than daytime PM at generating ·OH. Transition metals played the dominant role in ·OH production: on average (± σ), the addition of desferoxamine (a chelator that prevents metals from forming ·OH) to the SLF removed (90 ± 5) % of ·OH generation. Furthermore, based on the concentrations of Fe in the PM2.5 SLF extracts, and the measured yield of ·OH as a function of Fe concentration, dissolved iron can account for the majority of ·OH produced in most of our PM2.5 extracts. PMID:19245037

  14. Hydroxyl radical concentrations and Kuwait oil fire emission rates for March 1991

    NASA Astrophysics Data System (ADS)

    McKenna, D. S.; Hord, C. J.; Kent, J. M.

    1995-12-01

    Toward the end of the Gulf War, Iraqi troops damaged several hundred oil wells in Kuwait setting many of them on fire. Measurements made in March 1991, a few weeks after most of the fires had started (Johnson et al., 1991), were used to estimated the total burn rate and the emission rates of individual pollutants. Measurements of the principal carbon species in the plume, obtained from flask samples collected at the same time as continuous measurements of SO2 have been used to derive an "effective" sulphur content of the smoke of 2.4%, almost a third lower than the previous estimate. This sulphur content of 2.4% combined with the capping history of the fires has been used to revise the earlier estimates and provide more detailed information on the speciation of the emissions. It is now estimated that 139×106 t of crude oil were burnt during an 8-month period, resulting in the release of 112×106 t of carbon in carbon dioxide, 3×106 t of carbon in soot, 1.6×106 t of carbon in carbon monoxide, 1.3×106 t of carbon in nonmethane hydrocarbons, 0.11×106 t of nitrogen in nitrogen oxides, and 3.11×106 t of sulphur in sulphur dioxide. In addition to measurements made close to the source of the plume, one flight successfully sampled a plume some 600 km from the fires which had experienced significant photochemical aging. These observations provided a unique data set with which to estimate the rate at which hydrocarbon pollutants in the plume degrade and to infer the hydroxyl radical concentrations which cause that degradation. Most of the aliphatic hydrocarbon concentrations determined from flask samples collected at a range of distances from the Kuwait source conform to a simple loss process proportional to hydrocarbon hydroxyl reactivity and imply a diurnally averaged hydroxyl radical concentration within the plume of 1×106 molecules cm-3. Finally, it is shown that, although theoretically, hydrocarbon concentrations can be combined to predict the difference ratio of

  15. Production of sulfate radical and hydroxyl radical by reaction of ozone with peroxymonosulfate: a novel advanced oxidation process.

    PubMed

    Yang, Yi; Jiang, Jin; Lu, Xinglin; Ma, Jun; Liu, Yongze

    2015-06-16

    In this work, simultaneous generation of hydroxyl radical (•OH) and sulfate radical (SO4•−) by the reaction of ozone (O3) with peroxymonosulfate (PMS; HSO5−) has been proposed and experimentally verified. We demonstrate that the reaction between the anion of PMS (i.e.,SO52−) and O3 is primarily responsible for driving O3 consumption with a measured second order rate constant of (2.12 ± 0.03) × 10(4) M(-1) s(-1). The formation of both •OH and SO4•− from the reaction between SO52− and O3 is confirmed by chemical probes (i.e., nitrobenzene for •OH and atrazine forb oth •OH and SO4•−). The yields of •OH and SO4•− are determined to be 0.43 ± 0.1 and 0.45 ± 0.1 per mol of O3 consumption, respectively. An adduct,−O3SOO− + O3 → −O3SO5−, is assumed as the first step, which further decomposes into SO5•− and O3•−. The subsequent reaction of SO5•− with O3is proposed to generate SO4•−, while O3•− converts to •OH. A definition of R(ct,•OH) and R(ct,SO4•−) (i.e., respective ratios of •OH and SO4•− exposures to O3 exposure) is adopted to quantify relative contributions of •OH and SO4•−. Increasing pH leads to increases in both values of R(ct,•OH) and R(ct,SO4•−) but does not significantly affect the ratio of R(ct,SO4•−) to R(ct,•OH) (i.e., R(ct,SO4•−)/R(ct,•OH)), which represents the relative formation of SO4•− to •OH. The presence of bicarbonate appreciably inhibits the degradation of probes and fairly decreases the relative contribution of •OH for their degradation, which may be attributed to the conversion of both •OH and SO4•− to the more selective carbonate radical (CO3•−).Humic acid promotes O3 consumption to generate •OH and thus leads to an increase in the R(ct,•OH) value in the O3/PMS process,w hile humic acid has negligible influence on the R(ct,SO4•−) value. This discrepancy is reasonably explained by the negligible effect of humic acid on SO

  16. Pectic polysaccharides are attacked by hydroxyl radicals in ripening fruit: evidence from a fluorescent fingerprinting method

    PubMed Central

    Fry, Stephen C.

    2016-01-01

    Background and aims Many fruits soften during ripening, which is important commercially and in rendering the fruit attractive to seed-dispersing animals. Cell-wall polysaccharide hydrolases may contribute to softening, but sometimes appear to be absent. An alternative hypothesis is that hydroxyl radicals (•OH) non-enzymically cleave wall polysaccharides. We evaluated this hypothesis by using a new fluorescent labelling procedure to ‘fingerprint’ •OH-attacked polysaccharides. Methods We tagged fruit polysaccharides with 2-(isopropylamino)-acridone (pAMAC) groups to detect (a) any mid-chain glycosulose residues formed in vivo during •OH action and (b) the conventional reducing termini. The pAMAC-labelled pectins were digested with Driselase, and the products resolved by high-voltage electrophoresis and high-pressure liquid chromatography. Key Results Strawberry, pear, mango, banana, apple, avocado, Arbutus unedo, plum and nectarine pectins all yielded several pAMAC-labelled products. GalA–pAMAC (monomeric galacturonate, labelled with pAMAC at carbon-1) was produced in all species, usually increasing during fruit softening. The six true fruits also gave pAMAC·UA-GalA disaccharides (where pAMAC·UA is an unspecified uronate, labelled at a position other than carbon-1), with yields increasing during softening. Among false fruits, apple and strawberry gave little pAMAC·UA-GalA; pear produced it transiently. Conclusions GalA–pAMAC arises from pectic reducing termini, formed by any of three proposed chain-cleaving agents (•OH, endopolygalacturonase and pectate lyase), any of which could cause its ripening-related increase. In contrast, pAMAC·UA-GalA conjugates are diagnostic of mid-chain oxidation of pectins by •OH. The evidence shows that •OH radicals do indeed attack fruit cell wall polysaccharides non-enzymically during softening in vivo. This applies much more prominently to drupes and berries (true fruits) than to false fruits (swollen

  17. Phenylalanine as a hydroxyl radical-specific probe in pyrite slurries.

    PubMed

    Fisher, Shawn C; Schoonen, Martin Aa; Brownawell, Bruce J

    2012-02-07

    The abundant iron sulfide mineral pyrite has been shown to catalytically produce hydrogen peroxide (H2O2) and hydroxyl radical (.OH) in slurries of oxygenated water. Understanding the formation and fate of these reactive oxygen species is important to biological and ecological systems as exposure can lead to deleterious health effects, but also environmental engineering during the optimization of remediation approaches for possible treatment of contaminated waste streams. This study presents the use of the amino acid phenylalanine (Phe) to monitor the kinetics of pyrite-induced .OH formation through rates of hydroxylation forming three isomers of tyrosine (Tyr) - ortho-, meta-, and para-Tyr. Results indicate that about 50% of the Phe loss results in Tyr formation, and that these products further react with .OH at rates comparable to Phe. The overall loss of Phe appeared to be pseudo first-order in [Phe] as a function of time, but for the first time it is shown that initial rates were much less than first-order as a function of initial substrate concentration, [Phe]o. These results can be rationalized by considering that the effective concentration of .OH in solution is lower at a higher level of reactant and that an increasing fraction of .OH is consumed by Phe-degradation products as a function of time. A simplified first-order model was created to describe Phe loss in pyrite slurries which incorporates the [Phe]o, a first-order dependence on pyrite surface area, the assumption that all Phe degradation products compete equally for the limited supply of highly reactive .OH, and a flux that is related to the release of H2O2 from the pyrite surface (a result of the incomplete reduction of oxygen at the pyrite surface). An empirically derived rate constant, Kpyr, was introduced to describe a variable .OH-reactivity for different batches of pyrite. Both the simplified first-order kinetic model, and a more detailed numerical simulation, yielded results that compare well

  18. The fate of the hydroxyl radical in the earth's primitive atmosphere and implications for the production of molecular oxygen

    NASA Technical Reports Server (NTRS)

    Vander Wood, T. B.; Thiemens, M. H.

    1980-01-01

    Behavior of the hydroxyl radical produced by the photolysis of water vapor in the earth's early atmosphere is examined. Because of the substantial OH radical reactivity with trace species (CO, HCl, SO2, H2S, NH3, and CH4) the formation of molecular oxygen may be prevented, even at a trace species mixing ratio. The photolysis rate of H2O, with corrections for hydrogen exospheric escape, is capable of describing the oxidation of the atmosphere and crust but may not be used to determine the rate of molecular oxygen generation without consideration of the various OH-trace species reactions.

  19. Shock tube study of the reactions of the hydroxyl radical with combustion species and pollutants. Final report

    SciTech Connect

    Cohen, N.; Koffend, J.B.

    1998-02-01

    Shock heating t-butyl hydroperoxide behind a reflected shock wave has proved to be as a convenient source of hydroxyl radicals at temperatures near 1000 K. We applied this technique to the measurement of reaction rate coefficients of OH with several species of interest in combustion chemistry, and developed a thermochemical kinetics/transition state theory (TK-TST) model for predicting the temperature dependence of OH rate coefficients.

  20. Modeling hydroxyl radical distribution and trialkyl phosphates oxidation in UV-H2O2 photoreactors using computational fluid dynamics.

    PubMed

    Santoro, Domenico; Raisee, Mehrdad; Moghaddami, Mostafa; Ducoste, Joel; Sasges, Micheal; Liberti, Lorenzo; Notarnicola, Michele

    2010-08-15

    Advanced Oxidation Processes (AOPs) promoted by ultraviolet light are innovative and potentially cost-effective solutions for treating persistent pollutants recalcitrant to conventional water and wastewater treatment. While several studies have been performed during the past decade to improve the fundamental understanding of the UV-H(2)O(2) AOP and its kinetic modeling, Computational Fluid Dynamics (CFD) has only recently emerged as a powerful tool that allows a deeper understanding of complex photochemical processes in environmental and reactor engineering applications. In this paper, a comprehensive kinetic model of UV-H(2)O(2) AOP was coupled with the Reynolds averaged Navier-Stokes (RANS) equations using CFD to predict the oxidation of tributyl phosphate (TBP) and tri(2-chloroethtyl) phosphate (TCEP) in two different photoreactors: a parallel- and a cross-flow UV device employing a UV lamp emitting primarily 253.7 nm radiation. CFD simulations, obtained for both turbulent and laminar flow regimes and compared with experimental data over a wide range of UV doses, enabled the spatial visualization of hydrogen peroxide and hydroxyl radical distributions in the photoreactor. The annular photoreactor displayed consistently better oxidation performance than the cross-flow system due to the absence of recirculation zones, as confirmed by the hydroxyl radical dose distributions. Notably, such discrepancy was found to be strongly dependent on and directly correlated with the hydroxyl radical rate constant becoming relevant for conditions approaching diffusion-controlled reaction regimes (k(C,OH) > 10(9) M(-1) s(-1)).

  1. Protein oxidation: identification and utilisation of molecular markers to differentiate singlet oxygen and hydroxyl radical-mediated oxidative pathways.

    PubMed

    Plowman, Jeffrey E; Deb-Choudhury, Santanu; Grosvenor, Anita J; Dyer, Jolon M

    2013-11-01

    The effect of reactive oxidation species (ROS) on tryptophan or tyrosine was investigated by qualitatively determining the major detectable oxidation products generated by hydroxyl radicals, produced by the Fenton process, or singlet oxygen, generated by exposure to green light in the presence of Rose Bengal, on these photosensitive amino acids in synthetic pentapeptides. Based on mass spectrometric analysis it would appear that the hydroxyl radical favours a pathway leading to the formation of tryptophandione-based products from tryptophan. In contrast singlet oxygen attack appears to favour the formation of kynurenine-type products from tryptophan. Specific oxidative products observed proteomically are therefore potentially able to discriminate between predominant ROS-mediated pathways. To validate these findings, a keratin-enriched extract was exposed to UVB light under aqueous conditions. The observation of the conversion of tryptophan to hydroxytryptophan in marker peptides, and the absence of singlet-oxygen specific modifications, suggested that under these conditions oxidative degradation occurred primarily via hydroxyl radical attack. These observations provide the first direct proteomic evidence of the dominant photodegradation pathways in wet wool.

  2. Effects of tetrathiomolybdate and penicillamine on brain hydroxyl radical and free copper levels: a microdialysis study in vivo.

    PubMed

    Zhang, Ji-Wei; Liu, Jun-Xiu; Hou, Hai-Man; Chen, Ding-Bang; Feng, Li; Wu, Chao; Wei, Li-Ting; Li, Xun-Hua

    2015-02-27

    Wilson disease is an inherited disorder of excessive copper accumulation. The commonly used drug d-penicillamine (PA) or trientine both cause a high incidence (10-50%) of neurological worsening, which rarely occurs with tetrathiomolybdate (TM) treatment. To investigate the mechanisms of neurologic deterioration after the initiation of chelation therapy, brain hydroxyl radical and free copper were assessed in vivo in this study. On days 3, 7, 14, and 21 after PA or TM administration, striatal hydroxyl radical levels of both TX mice and controls were assessed by terephthalic acid (TA) combined with microdialysis and high-performance liquid chromatography (HPLC). Within the same microdialysis samples, free copper was measured by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that both hydroxyl radical and free copper markedly increased in the striatum of TX mice during PA administration but were not elevated when administering TM. These results suggested that the further increased free copper in the brain and oxidative stress caused by some chelators might contribute to the neurological deterioration.

  3. Inhibition effect of chlorine ion on hydroxyl radical generation in UV-H2O2 process.

    PubMed

    Tsuneda, S; Ishihara, Y; Hamachi, M; Hirata, A

    2002-01-01

    UV-H2O2 process is widely used as an advanced oxidation process (AOP) for the treatment of chlorine volatile organic compounds (CVOCs) such as dichloromethane (DCM) with strong oxidativity of hydroxyl radical generated from photolysis of H2O2. The result of DCM degradation rate at different initial concentrations in UV-H2O2 processes indicated the inhibition effect of produced chlorine ions on DCM oxidation processes, because the first-order degradation rate constant increased with lower initial concentrations. A spin trapping adduct of hydroxyl radical with 5,5-dimethyl-1-pyrroline-n-oxide (DMPO) was quantified by ESR spectrometer after UV irradiation in the presence of different amounts of chlorine ion, and as a result, the chlorine ion was found to act as a hydroxyl radical scavenger, which resulted in decreasing DCM degradation rate. An UV-H2O2 reactor equipped with ion exchangers for removing chlorine ion achieved higher DCM degradation rate than that without ion exchangers.

  4. Hydroxyl Radical Regeneration in Isoprene Oxidation: the Upgraded Mechanism LIM1

    NASA Astrophysics Data System (ADS)

    Peeters, J.; Nguyen, S.; Nguyen, T.; Stavrakou, T.; Muller, J. J.

    2012-12-01

    Measured hydroxyl radical concentrations in isoprene-rich areas are much higher than predicted by existing chemical models, to the extent that the global oxidizing capacity of our atmosphere should be significantly revised upwards. The OH regeneration that clearly occurs in isoprene oxidation at low/moderate NO is attributed in the Leuven Isoprene Mechanism to novel, theoretically characterized chemical pathways (LIM0: Peeters et al. 2009; Peeters and Muller 2010). The key new features of LIM0 are (i) thermal equilibration of the labile beta-OH- and delta-OH-isoprenylperoxy isomers; (ii) 1,6-H shift isomerisation of the Z-delta-OH-peroxy isomers to yield hydroperoxy-methyl-butenals (HPALDs); (iii) fast photolysis of the HPALDs resulting overall in several OH radicals per HPALD. The OH-regeneration through photolabile HPALDs has recently found experimental support, but the peroxy isomerisation rate, HPALD yield and the extent of OH recycling are still uncertain (Crounse et al. 2011; Wolfe et al. 2012). In this work, the upgraded LIM1 mechanism is presented. Based on better levels of theory, the crucial equilibrium ratio of the isomerising Z-delta-OH-peroxys over the majority beta-OH-isoprenylperoxys had to be reduced by a factor of about 5 compared to LIM0, while the isomerisation rate of the Z-delta-OH-peroxys adopted from Taraborrelli et al. (2012) is about 3 times lower than in LIM0. The chemistry following the 1,6-H shift of the Z-delta-OH-peroxys is much expanded and extended. Firstly, LIM1 introduces other pathways beside HPALD formation following the Z-delta-OH-peroxy isomerisation, resulting likewise in OH recycling. This, together with the revised Z-delta-OH- equilibrium and isomerisation data above, affords a close model-reproduction of the HPALD and other product yields observed by Crounse et al. (2011). Secondly, LIM1 proposes new fast reactions of HO2 with the alpha-oxoketene products from the peroxy isomerisation routes; these reactions are shown to

  5. Anticancer effect of linalool via cancer-specific hydroxyl radical generation in human colon cancer

    PubMed Central

    Iwasaki, Kenichi; Zheng, Yun-Wen; Murata, Soichiro; Ito, Hiromu; Nakayama, Ken; Kurokawa, Tomohiro; Sano, Naoki; Nowatari, Takeshi; Villareal, Myra O; Nagano, Yumiko N; Isoda, Hiroko; Matsui, Hirofumi; Ohkohchi, Nobuhiro

    2016-01-01

    AIM To investigate the anticancer mechanisms of the monoterpenoid alcohol linalool in human colon cancer cells. METHODS The cytotoxic effect of linalool on the human colon cancer cell lines and a human fibroblast cell line was examined using the WST-8 assay. The apoptosis-inducing effect of linalool was measured using the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay and flow cytometry with Annexin V. Oxidative stress was investigated by staining for diphenyl-1-pyrenylphosphine, which is a cellular lipid peroxidation marker, and electron spin resonance spectroscopy. Sixteen SCID mice xenografted with human cancer cells were randomized into 3 groups for in vivo analysis: control and low-dose and high-dose linalool groups. The control group was administered tap water orally every 3 d. The linalool treatment groups were administered 100 or 200 μg/kg linalool solution orally for the same period. All mice were sacrificed under anesthesia 21 d after tumor inoculation, and tumors and organs were collected for immunohistochemistry using an anti-4-hydroxynonenal antibody. Tumor weights were measured and compared between groups. RESULTS Linalool induced apoptosis of cancer cells in vitro, following the cancer-specific induction of oxidative stress, which was measured based on spontaneous hydroxyl radical production and delayed lipid peroxidation. Mice in the high-dose linalool group exhibited a 55% reduction in mean xenograft tumor weight compared with mice in the control group (P < 0.05). In addition, tumor-specific lipid peroxidation was observed in the in vivo model. CONCLUSION Linalool exhibited an anticancer effect via cancer-specific oxidative stress, and this agent has potential for application in colon cancer therapy. PMID:27956800

  6. Treatment of TNT-contaminated soils using Fenton`s reagent generated hydroxyl radicals

    SciTech Connect

    Sherman, B.; Allen, H.E.; Huang, C.P.

    1995-12-31

    The oxidation of 2,4,6-trinitrotoluene (TNT) in soils using catalyzed hydrogen peroxide (Fenton`s reagent) was evaluated in laboratory-scale experiments. Three characterized soils, which varied in organic matter content were treated in batch experiments with a 1M hydrogen peroxide and 10 mM ferrous iron solution. Hydrogen peroxide slurry concentration of 1M was found to provide optimum degradation of TNT in soils. Slurry soil:solution ratio of 2:11 (w:w) was used and pH was maintained between 2 and 3. Compound degradation was monitored over 16 hours. Total mass of TNT was monitored by analyzing both the aqueous phase and sorbed phase. Greater than 95% of TNT was oxidized in all soils after eight hours of reaction time with a single treatment. The rate of TNT oxidation was shown to be slightly lower in the soil containing the highest percentage of organic matter, however, total oxidation after eight hours was the same for all three soils. The formation and oxidation of several oxidation products was also observed with HPLC and GC-MS. All oxidation products are intermediate products that existed in trace amounts relative to TNT and are therefore believed to not accumulate. Hydroxyl radical attack on TNT is initiated by hydrogen abstractions from the methyl group to form 2,4,6-trinitrobenzaldehyde, which then rapidly degrades to form other, currently unidentified, oxidation products. Advanced oxidation using Fenton`s reagent appears to be a promising treatment for TNT-contaminated soils.

  7. Improved Identification and Relative Quantification of Sites of Peptide and Protein Oxidation for Hydroxyl Radical Footprinting

    NASA Astrophysics Data System (ADS)

    Li, Xiaoyan; Li, Zixuan; Xie, Boer; Sharp, Joshua S.

    2013-11-01

    Protein oxidation is typically associated with oxidative stress and aging and affects protein function in normal and pathological processes. Additionally, deliberate oxidative labeling is used to probe protein structure and protein-ligand interactions in hydroxyl radical protein footprinting (HRPF). Oxidation often occurs at multiple sites, leading to mixtures of oxidation isomers that differ only by the site of modification. We utilized sets of synthetic, isomeric "oxidized" peptides to test and compare the ability of electron-transfer dissociation (ETD) and collision-induced dissociation (CID), as well as nano-ultra high performance liquid chromatography (nanoUPLC) separation, to quantitate oxidation isomers with one oxidation at multiple adjacent sites in mixtures of peptides. Tandem mass spectrometry by ETD generates fragment ion ratios that accurately report on relative oxidative modification extent on specific sites, regardless of the charge state of the precursor ion. Conversely, CID was found to generate quantitative MS/MS product ions only at the higher precursor charge state. Oxidized isomers having multiple sites of oxidation in each of two peptide sequences in HRPF product of protein Robo-1 Ig1-2, a protein involved in nervous system axon guidance, were also identified and the oxidation extent at each residue was quantified by ETD without prior liquid chromatography (LC) separation. ETD has proven to be a reliable technique for simultaneous identification and relative quantification of a variety of functionally different oxidation isomers, and is a valuable tool for the study of oxidative stress, as well as for improving spatial resolution for HRPF studies.

  8. Mechanisms of Sb(III) oxidation by pyrite-induced hydroxyl radicals and hydrogen peroxide.

    PubMed

    Kong, Linghao; Hu, Xingyun; He, Mengchang

    2015-03-17

    Antimony (Sb) is an element of growing interest, and its toxicity and mobility are strongly influenced by redox processes. Sb(III) oxidation mechanisms in pyrite suspensions were comprehensively investigated by kinetic measurements in oxic and anoxic conditions and simulated sunlight. Sb(III) was oxidized to Sb(V) in both solution and on pyrite surfaces in oxic conditions; the oxidation efficiency of Sb(III) was gradually enhanced with the increase of pH. The pyrite-induced hydroxyl radical (·OH) and hydrogen peroxide (H2O2) are the oxidants for Sb(III) oxidation. ·OH is the oxidant for Sb(III) oxidation in acidic solutions, and H2O2 becomes the main oxidant in neutral and alkaline solutions. ·OH and H2O2 can be generated by the reaction of previously existing FeIII(pyrite) and H2O on pyrite in anoxic conditions. The oxygen molecule is the crucial factor in continuously producing ·OH and H2O2 for Sb(III) oxidation. The efficiency of Sb(III) oxidation was enhanced in surface-oxidized pyrite (SOP) suspension, more ·OH formed through Fenton reaction in acidic solutions, but Fe(IV) and H2O2 were formed in neutral and alkaline solutions. Under the illumination of simulated sunlight, more ·OH and H2O2 were produced in the pyrite suspension, and the oxidation efficiency of Sb(III) was remarkably enhanced. In conclusion, Sb(III) can be oxidized to Sb(V) in the presence of pyrite, which will greatly influence the fate of Sb(III) in the environment.

  9. Identifying the factors that influence the reactivity of effluent organic matter with hydroxyl radicals.

    PubMed

    Keen, Olya S; McKay, Garrett; Mezyk, Stephen P; Linden, Karl G; Rosario-Ortiz, Fernando L

    2014-03-01

    Advanced oxidation processes (AOPs) are an effective treatment technology for the removal of a variety of organic pollutants in both water and wastewater treatment. However, many background constituents in water are highly reactive towards hydroxyl radicals (HO) and decrease the efficiency of the process towards contaminant oxidation. Up to 95% of the HO scavenging can come from dissolved organic matter (OM). In this study, 28 wastewater effluent samples were analyzed to find correlations between the reactivity of HO with wastewater-derived OM (known as effluent organic matter, EfOM), water quality parameters, treatment train characteristics, and fluorescence-derived data. Rate constants for the reaction between HO and EfOM (kEfOM-HO) were measured using a bench scale UV-based AOP system with methylene blue as an HO probe and confirmed using an electron pulse radiolysis method for a subset of the samples. The EfOM was characterized using a series of physicochemical parameters, including polarity, average molecular size and fluorescence. The kinetic data were analyzed with principal component analysis and Akaike Information Criterion. Four predictors were identified as dominant: chemical oxygen demand, retention onto NH2 extraction medium, fluorescence index, and total organic carbon. These four variables accounted for approximately 62% of the variability in the value of kEfOM-HO The average kEfOM-HO value for EfOM in this study was 2.5 × 10(8) MC(-1) s(-1), which is about 31% lower than the 3.6 × 10(8) MC(-1) s(-1) value determined for natural organic matter isolates and commonly used in AOP modeling.

  10. Elucidating in Vivo Structural Dynamics in Integral Membrane Protein by Hydroxyl Radical Footprinting*

    PubMed Central

    Zhu, Yi; Guo, Tiannan; Park, Jung Eun; Li, Xin; Meng, Wei; Datta, Arnab; Bern, Marshall; Lim, Sai Kiang; Sze, Siu Kwan

    2009-01-01

    We describe here a novel footprinting technique to probe the in vivo structural dynamics of membrane protein. This method utilized in situ generation of hydroxyl radicals to oxidize and covalently modify biomolecules on living Escherichia coli cell surface. After enriching and purifying the membrane proteome, the modified amino acid residues of the protein were identified with tandem mass spectrometry to map the solvent-accessible surface of the protein that will form the footprint of in vivo structure of the protein. Of about 100 outer membrane proteins identified, we investigated the structure details of a typical β-barrel structure, the porin OmpF. We found that six modified tryptic peptides of OmpF were reproducibly detected with 19 amino acids modified under the physiological condition. The modified amino acid residues were widely distributed in the external loop area, β-strands, and periplasmic turning area, and all of them were validated as solvent-accessible according to the crystallography data. We further extended this method to study the dynamics of the voltage gating of OmpF in vivo using mimic changes of physiological circumstance either by pH or by ionic strength. Our data showed the voltage gating of porin OmpF in vivo for the first time and supported the proposed mechanism that the local electrostatic field changes in the eyelet region may alter the porin channels to switch. Thus, this novel method can be a potentially efficient method to study the structural dynamics of the membrane proteins of a living cell. PMID:19473960

  11. Photometric hydroxyl radical scavenging analysis of standard natural organic matter isolates.

    PubMed

    Donham, J E; Rosenfeldt, E J; Wigginton, K R

    2014-04-01

    Hydroxyl radical (˙OH) scavenging reaction rate constants of standard natural organic matter (NOM) isolates (k˙OH,NOM) were measured with a rapid background scavenging method, to expand the dataset of published k˙OH,NOM values. The proposed method relies on ˙OH generation with a simple UV/H₂O₂ AOP-based system. The associated decay of a ˙OH probe compound is monitored with a field-deployable spectrophotometer and k˙OH,NOM is determined through competition kinetics. The resulting k˙OH,NOM values for the six NOM standard isolates ranged from 1.02 (±0.10) × 10(8) MC(-1) s(-1) for Suwannee River Fulvic Acid I Standard to 2.03 (±0.12) × 10(8) MC(-1) s(-1) for Pony Lake Fulvic Acid Reference NOM, which is within the range reported with more elaborate and time-consuming k˙OH,NOM methods. A slight correlation between nitrogen content and scavenging rate constant was evident while no significant correlation between k˙OH,NOM and atomic composition, carbon structure, weight-average molecular weight, UV absorbance (SUVA₂₅₄), or fluorescence index (FI) was observed. Overall, the results demonstrate that k˙OH,NOM can be rapidly assessed in NOM isolate samples. The results suggest that this type of rapid field-deployable spectrophotometric method may minimize the need for expensive and time-consuming background scavenging methods, and for models that predict k˙OH,NOM based on other NOM characteristics.

  12. Scavenging property of three cresol isomers against H2O2, hypochlorite, superoxide and hydroxyl radicals.

    PubMed

    Yeung, S Y; Lan, W H; Huang, C S; Lin, C P; Chan, C P; Chang, M C; Jeng, J H

    2002-10-01

    Formocresol has long been used for pulpotomy of primary teeth and as an intracanal medicament. Little is known, however, about the pharmacological effect of tricresols. This study showed that three cresol isomers, o-cresol, m-cresol and p-cresol, are H2O2 scavengers with a 50% inhibitory concentration (IC50) of 502, 6.7 and 10.16 microM, respectively. o-, m- and p-cresol were also shown to be effective scavengers of superoxide radicals generated by xanthine/xanthine oxidase with an IC50 of 282, 153 and > 4000 microM, respectively, as analyzed by luminometer. o-, m- and p-cresol showed protective effects on the DNA breaks generated by H2O2/FeCl2 and FeCl3/ascorbate/H2O2 systems at concentrations ranging from 70 microM to 1.43 mM, o-, m- and p-cresol also showed differential protective effects against DNA breaks induced by 0.17% NaOCl with 100% inhibitory concentration (IC100) of about 10, 1 and 10 mM, respectively. In addition, reaction with 3% H2O2 and 0.17% NaOCl completely prevented NaOCl-induced DNA breaks. The results indicate that the three cresol isomers are effective ROS scavengers and may prevent ROS induced damage when used as pulpotomy agents or as intracanal medicaments. Owing to the difference in the position of the functional hydroxyl group in the three cresol isomers, m-cresol is the most effective ROS scavenger. Concomitant use of H2O2 for root canal irrigation may diminish both the tissue dissolving capacity of NaOCl and NaOCl-induced DNA damage.

  13. The antagonistic effect of hydroxyl radical on the development of a hypersensitive response in tobacco.

    PubMed

    Deng, Sheng; Yu, Mina; Wang, Ying; Jia, Qin; Lin, Ling; Dong, Hansong

    2010-12-01

    Reactive oxygen species (ROS) are important signalling molecules in living cells. It is believed that ROS molecules are the main triggers of the hypersensitive response (HR) in plants. In the present study of the effect of riboflavin, which is excited to generate ROS in light, on the development of the HR induced by the elicitin protein ParA1 in tobacco (Nicotiana tabacum), we found that the extent of the ParA1-induced HR was diminished by hydroxyl radical (OH•), a type of ROS. As compared with the zones treated with ParA1 only, the HR symptom in the zones that were infiltrated with ParA1 plus riboflavin was significantly diminished when the treated plants were placed in the light. However, this did not occur when the plants were maintained in the dark. Trypan blue staining and the ion leakage measurements confirmed HR suppression in the light. Further experiments proved that HR suppression is attributed to the involvement of the photoexcited riboflavin, and that the suppression can be eliminated with the addition of hydrogen peroxide scavengers or OH• scavengers. Fenton reagent treatment and EPR measurements demonstrated that it is OH• rather than hydrogen peroxide that contributes to HR suppression. Accompanying the endogenous OH• formation, suppression of the ParA1-induced HR occurred in the tobacco leaves that had been treated with high-level abscisic acid, and that suppression was also removed by OH• scavengers. These results offer evidence that OH•, an understudied and little appreciated ROS, participates in and modulates biologically relevant signalling in plant cells.

  14. Phytic acid suppresses ischemia-induced hydroxyl radical generation in rat myocardium.

    PubMed

    Obata, Toshio; Nakashima, Michiko

    2016-03-05

    The present study examined whether ischemia-reperfusion-induced hydroxyl radical (·OH) generation was attenuated by myo-inositol hexaphosphoric acid (phytic acid). A flexibly mounted microdialysis technique was used to detect the generation of ·OH in in vivo rat hearts. To measure the level of ·OH, sodium salicylate in Ringer's solution (0.5mM or 0.5 nmol/μl/min) was infused directly through a microdialysis probe to detect the generation of ·OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (2,3-DHBA). To confirm the generation of ·OH by Fenton-type reaction, iron(II) was infused through a microdialysis probe. A positive linear correlation between iron(II) and the formation of 2,3-DHBA (R(2)=0.983) was observed. However, the level of 2,3-DHBA in norepinephrine (100 μM) plus phytic acid (100 μM) treated group were significantly lower than those observed in norepinephrine-only-treated group (n=6, *p<0.05). To examine the effect of phytic acid on ischemia-reperfusion-induced ·OH generation, the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery (LAD). When the heart was reperfused, the normal elevation of 2,3-DHBA in the heart dialysate was not observed in animals pretreated with phytic acid. These results suggest that phytic acid is associated with antioxidant effect due to the suppression of iron-induced ·OH generation.

  15. Generation of Hydroxyl Radicals from Dissolved Transition Metals in Surrogate Lung Fluid Solutions

    PubMed Central

    Vidrio, Edgar; Jung, Heejung; Anastasio, Cort

    2008-01-01

    Epidemiological research has linked exposure to atmospheric particulate matter (PM) to several adverse health effects, including cardiovascular and pulmonary morbidity and mortality. Despite these links, the mechanisms by which PM causes adverse health effects are poorly understood. The generation of hydroxyl radical (·OH) and other reactive oxygen species (ROS) through transition metal-mediated pathways is one of the main hypotheses for PM toxicity. In order to better understand the ability of particulate transition metals to produce ROS, we have quantified the amounts of ·OH produced from dissolved iron and copper in a cell-free, surrogate lung fluid (SLF). We also examined how two important biological molecules, citrate and ascorbate, affect the generation of ·OH by these metals. We have found that Fe(II) and Fe(III) produce little ·OH in the absence of ascorbate and citrate, but that they efficiently make ·OH in the presence of ascorbate and this is further enhanced when citrate is also added. In the presence of ascorbate, with or without citrate, the oxidation state of iron makes little difference on the amount of ·OH formed after 24 hours. In the case of Cu(II), the production of ·OH is greatly enhanced in the presence of ascorbate, but is inhibited by the addition of citrate. The mechanism for this effect is unclear, but appears to involve formation of a citrate-copper complex that is apparently less reactive than free, aquated copper in either the generation of HOOH or in the Fenton-like reaction of copper with HOOH to make ·OH. By quantifying the amount of ·OH that Fe and Cu can produce in surrogate lung fluid, we have provided a first step into being able to predict the amounts of ·OH that can be produced in the human lung from exposure to PM containing known amounts of transition metals. PMID:19148304

  16. Generation of Hydroxyl Radicals from Dissolved Transition Metals in Surrogate Lung Fluid Solutions.

    PubMed

    Vidrio, Edgar; Jung, Heejung; Anastasio, Cort

    2008-01-01

    Epidemiological research has linked exposure to atmospheric particulate matter (PM) to several adverse health effects, including cardiovascular and pulmonary morbidity and mortality. Despite these links, the mechanisms by which PM causes adverse health effects are poorly understood. The generation of hydroxyl radical (.OH) and other reactive oxygen species (ROS) through transition metal-mediated pathways is one of the main hypotheses for PM toxicity. In order to better understand the ability of particulate transition metals to produce ROS, we have quantified the amounts of .OH produced from dissolved iron and copper in a cell-free, surrogate lung fluid (SLF). We also examined how two important biological molecules, citrate and ascorbate, affect the generation of .OH by these metals. We have found that Fe(II) and Fe(III) produce little .OH in the absence of ascorbate and citrate, but that they efficiently make .OH in the presence of ascorbate and this is further enhanced when citrate is also added. In the presence of ascorbate, with or without citrate, the oxidation state of iron makes little difference on the amount of .OH formed after 24 hours. In the case of Cu(II), the production of .OH is greatly enhanced in the presence of ascorbate, but is inhibited by the addition of citrate. The mechanism for this effect is unclear, but appears to involve formation of a citrate-copper complex that is apparently less reactive than free, aquated copper in either the generation of HOOH or in the Fenton-like reaction of copper with HOOH to make .OH. By quantifying the amount of .OH that Fe and Cu can produce in surrogate lung fluid, we have provided a first step into being able to predict the amounts of .OH that can be produced in the human lung from exposure to PM containing known amounts of transition metals.

  17. Hydrogen peroxide-mediated degradation of protein: different oxidation modes of copper- and iron-dependent hydroxyl radicals on the degradation of albumin.

    PubMed

    Kocha, T; Yamaguchi, M; Ohtaki, H; Fukuda, T; Aoyagi, T

    1997-02-08

    Cupric ions (Cu2+) added to hydrogen peroxide (H2O2) were found to generate hydroxyl radicals (HO) capable of benzoate hydroxylation. Although ferrous (Fe2+) and ferric (Fe3+) ions, when added to H2O2, resulted in very little production of HO, the addition of EDTA to the reaction mixture markedly increased their catalytic activity. In the absence of albumin, catalase (a H2O2 scavenger) and mannitol (an HO radical scavenger) effectively inhibited the formation of HO in H2O2/Cu2+ and H2O2/Fe2+/EDTA oxidation systems. On analysis using SDS-polyacrylamide gel electrophoresis, catalase was shown to prevent the degradation of albumin by both oxidation systems, whereas mannitol was an effective scavenger of the H2O2/Fe2+/EDTA oxidation system but not of the H2O2/Cu2+ oxidation system. Furthermore, the effect of alteration of benzoate hydroxylation and H2O2 consumption on the H2O2/Cu2+ and H2O2/Fe2+/EDTA oxidation systems resulted in opposite behavior that was dependent upon the presence or absence of albumin. These observations suggest that copper ions bind to albumin and induce site-specific degradation by HO generated at the copper-binding site, whereas the Fe2+/EDTA-catalyzed oxidation system induces non-specific degradation of albumin by HO generated by the Fenton reaction between H2O2 and free Fe2+/EDTA in solution.

  18. Reaction kinetics and efficiencies for the hydroxyl and sulfate radical based oxidation of artificial sweeteners in water.

    PubMed

    Toth, Janie E; Rickman, Kimberly A; Venter, Andre R; Kiddle, James J; Mezyk, Stephen P

    2012-10-11

    Over the past several decades, the increased use of artificial sweeteners as dietary supplements has resulted in rising concentrations of these contaminants being detected in influent waters entering treatment facilities. As conventional treatments may not quantitatively remove these sweeteners, radical-based advanced oxidation and reduction (AO/RP) treatments could be a viable alternative. In this study, we have established the reaction kinetics for both hydroxyl ((•)OH) and sulfate (SO(4)(•-)) radical reaction with five common artificial sweeteners, as well as their associated reaction efficiencies. Rate constants for acesulfame K, aspartame, rebaudioside A, saccharin, and sucralose were <2 × 10(7), (2.28 ± 0.02) × 10(9), (2.1 ± 0.1) × 10(8), <2 × 10(7), and (1.7 ± 0.1) × 10(8) M(-1) s(-1) for the sulfate radical, and (3.80 ± 0.27) × 10(9), (6.06 ± 0.05) × 10(9), (9.97 ± 0.12) × 10(9), (1.85 ± 0.01) × 10(9), and (1.50 ± 0.01) × 10(9) M(-1) s(-1) for the hydroxyl radical, respectively. These latter values have to be combined with their corresponding reaction efficiencies of 67.9 ± 0.9, 52.2 ± 0.7, 43.0 ± 2.5, 52.7 ± 2.9, and 98.3 ± 3.5% to give effective rate constants for the hydroxyl radical reaction that can be used in the modeling of the AOP based removal of these contaminants.

  19. Contribution of the photo-Fenton reaction to hydroxyl radical formation rates in river and rain water samples.

    PubMed

    Nakatani, Nobutake; Ueda, Marina; Shindo, Hirotaka; Takeda, Kazuhiko; Sakugawa, Hiroshi

    2007-09-01

    The hydroxyl radical (OH radical) formation rates from the photo-Fenton reaction in river and rain water samples were determined by using deferoxamine mesylate (DFOM), which makes a stable and strong complex with Fe(III), resulting in a suppression of the photo-Fenton reaction. The difference between the OH radical formation rates with and without added DFOM denotes the rate from the photo-Fenton reaction. The photoformation rates from the photo-Fenton reaction were in the range of 0.7 - 45.8 x 10(-12) and 2.7 - 32.3 x 10(-12) M s(-1) in river and rain water samples, respectively. A strong positive correlation between the OH radical formation rate from the photo-Fenton reaction and the amount of fluorescent matter in river water suggests that fluorescent matter, such as humic substances, plays an important role in the photo-Fenton reaction. In rain water, direct photolysis of hydrogen peroxide was an important source of OH radicals as well as the photo-Fenton reaction. The contributions of the photo-Fenton reaction to the OH radical photoformation rates in river and rain water samples were in the ranges of 2 - 29 and 5 - 38%, respectively. Taking into account the photo-Fenton reaction, 33 - 110 (mean: 80) and 42 - 110 (mean: 84)% of OH radical sources in river and rain water samples, respectively, collected in Hiroshima prefecture were elucidated.

  20. Hydroxyl radical formation during ozonation of multiwalled carbon nanotubes: performance optimization and demonstration of a reactive CNT filter.

    PubMed

    Oulton, Rebekah; Haase, Jason P; Kaalberg, Sara; Redmond, Connor T; Nalbandian, Michael J; Cwiertny, David M

    2015-03-17

    We explored factors influencing hydroxyl radical (•OH) formation during ozonation of multiwalled carbon nanotubes (MWCNTs) and assessed this system's viability as a next-generation advanced oxidation process (AOP). Using standard reactivity metrics for ozone-based AOPs (RCT values), MWCNTs promoted •OH formation during ozonation to levels exceeding ozone (both alone and with activated carbon) and equivalent to ozone with hydrogen peroxide. MWCNTs oxidized with nitric acid exhibited vastly greater rates of ozone consumption and •OH formation relative to as-received MWCNTs. While some of this enhancement reflects their greater suspension stability, a strong correlation between RCT values and surface oxygen concentrations from X-ray photoelectron spectroscopy suggests that surface sites generated during MWCNT oxidation promote •OH exposure. Removal of several ozone-recalcitrant species [para-chlorobenzoic acid (p-CBA), atrazine, DEET, and ibuprofen] was not significantly inhibited in the presence of radical scavengers (humic acid, carbonate), in complex aquatic matrices (Iowa River water) and after 12 h of continuous exposure of MWCNTs to concentrated ozone solutions. As a proof-of-concept, oxidized MWCNTs deposited on a ceramic membrane chemically oxidized p-CBA in a flow through system, with removal increasing with influent ozone concentration and mass of deposited MWCNTs (in mg/cm2). This hybrid membrane platform, which integrates adsorption, oxidation, and filtration via an immobilized MWCNT layer, may serve as the basis for future novel nanomaterial-enabled technologies, although long-term performance trials under representative treatment scenarios remain necessary.

  1. Impacts of global emissions of CO, NO x , and CH4 on China tropospheric hydroxyl free radicals

    NASA Astrophysics Data System (ADS)

    Su, Mingfeng; Lin, Yunping; Fan, Xinqiang; Peng, Li; Zhao, Chunsheng

    2012-07-01

    Using the global chemistry and transport model MOZART, the simulated distributions of tropospheric hydroxyl free radicals (OH) over China and its sensitivities to global emissions of carbon monoxide (CO), nitrogen oxide (NO x ), and methane (CH4) were investigated in this study. Due to various distributions of OH sources and sinks, the concentrations of tropospheric OH in east China are much greater than in west China. The contribution of NO + perhydroxyl radical (HO2) reaction to OH production in east China is more pronounced than that in west China, and because of the higher reaction activity of non-methane volatile organic compounds (NMVOCs), the contributions to OH loss by NMVOCs exceed those of CO and take the dominant position in summer. The results of the sensitivity runs show a significant increase of tropospheric OH in east China from 1990 to 2000, and the trend continues. The positive effect of double emissions of NO x on OH is partly offset by the contrary effect of increased CO and CH4 emissions: the double emissions of NO x will cause an increase of OH of 18.1%-30.1%, while the increases of CO and CH4 will cause a decrease of OH of 12.2%-20.8% and 0.3%-3.0%, respectively. In turn, the lifetimes of CH4, CO, and NO x will increase by 0.3%-3.1% with regard to double emissions of CH4, 13.9%-26.3% to double emissions of CO and decrease by 15.3%-23.2% to double emissions of NO x .

  2. New Oxidovanadium Complexes Incorporating Thiosemicarbazones and 1, 10-Phenanthroline Derivatives as DNA Cleavage, Potential Anticancer Agents, and Hydroxyl Radical Scavenger.

    PubMed

    Ying, Peng; Zeng, Pengfei; Lu, Jiazheng; Chen, Hongyuan; Liao, Xiangwen; Yang, Ning

    2015-10-01

    Four novel oxidovanadium(IV) complexes, [VO(hntdtsc)(PHIP)] (1) (hntdtsc = 2-hydroxy-1-naphthaldehyde thiosemicarbazone, PHIP= 2-phenyl-imidazo[4,5-f]1,10-phenanthroline), [VO(hntdtsc)(DPPZ)](2)(DPPZ= dipyrido[3,2-a:2',3'-c]phenazine), [VO(satsc)(PHIP)](3) (satsc=salicylaldehyde thiosemicarbazone), and [VO(satsc)(DPPZ)](4), have been prepared and characterized. The chemical nuclease activities and photocleavage reactions of the complexes were tested. All four complexes can efficiently cleave pBR322 DNA, and complex 1 has the best cleaving ability. The antitumor properties of these complexes were examined with three different tumor cell lines using MTT assay. Their antitumor mechanism has been analyzed using cell cycle analysis, fluorescence microscopy of apoptosis, and Annexin V-FITC/PI assay. The results showed that the growth of human neuroblastoma (SH-SY5Y, SK-N-SH) and human breast adenocarcinoma (MCF-7) cells were inhibited significantly with very low IC50 values. Complex 1 was found to be the most potent antitumor agent among the four complexes. It can cause G0/G1 phase arrest of the cell cycle and exhibited significant induced apoptosis in SK-N-SH cells and displayed typical morphological apoptotic characteristics. In addition, they all displayed reasonable abilities to scavenge hydroxyl radical, and complex 1 was the best inhibitor.

  3. Enhanced hydroxyl radical generation in the combined ozonation and electrolysis process using carbon nanotubes containing gas diffusion cathode.

    PubMed

    Wu, Donghai; Lu, Guanghua; Zhang, Ran; Lin, Qiuhong; Yan, Zhenhua; Liu, Jianchao; Li, Yi

    2015-10-01

    Combination of ozone together with electrolysis (ozone-electrolysis) is a promising wastewater treatment technology. This work investigated the potential use of carbon nanotube (CNT)-based gas diffusion cathode (GDC) for ozone-electrolysis process employing hydroxyl radicals (·OH) production as an indicator. Compared with conventional active carbon (AC)-polytetrafluoroethylene (PTFE) and carbon black (CB)-PTFE cathodes, the production of ·OH in the coupled process was improved using CNTs-PTFE GDC. Appropriate addition of acetylene black (AB) and pore-forming agent Na2SO4 could enhance the efficiency of CNTs-PTFE GDC. The optimum GDC composition was obtained by response surface methodology (RSM) analysis and was determined as CNTs 31.2 wt%, PTFE 60.6 wt%, AB 3.5 wt%, and Na2SO4 4.7 wt%. Moreover, the optimized CNT-based GDC exhibited much more effective than traditional Ti and graphite cathodes in Acid Orange 7 (AO7) mineralization and possessed the desirable stability without performance decay after ten times reaction. The comparison tests revealed that peroxone reaction was the main pathway of ·OH production in the present system, and cathodic reduction of ozone could significantly promote ·OH generation. These results suggested that application of CNT-based GDC offers considerable advantages in ozone-electrolysis of organic wastewater.

  4. Silver Coordination Polymers for Prevention of Implant Infection: Thiol Interaction, Impact on Respiratory Chain Enzymes, and Hydroxyl Radical Induction▿ †

    PubMed Central

    Gordon, Oliver; Vig Slenters, Tünde; Brunetto, Priscilla S.; Villaruz, Amer E.; Sturdevant, Daniel E.; Otto, Michael; Landmann, Regine; Fromm, Katharina M.

    2010-01-01

    Prosthetic joint replacements are used increasingly to alleviate pain and improve mobility of the progressively older and more obese population. Implant infection occurs in about 5% of patients and entails significant morbidity and high social costs. It is most often caused by staphylococci, which are introduced perioperatively. They are a source of prolonged seeding and difficult to treat due to antibiotic resistance; therefore, infection prevention by prosthesis coating with nonantibiotic-type anti-infective substances is indicated. A renewed interest in topically used silver has fostered development of silver nanoparticles, which, however, present a potential health hazard. Here we present new silver coordination polymer networks with tailored physical and chemical properties as nanostructured coatings on metallic implant substrates. These compounds exhibited strong biofilm sugar-independent bactericidal activity on in vitro-grown biofilms and prevented murine Staphylococcus epidermidis implant infection in vivo with slow release of silver ions and limited transient leukocyte cytotoxicity. Furthermore, we describe the biochemical and molecular mechanisms of silver ion action by gene screening and by targeting cell metabolism of S. epidermidis at different levels. We demonstrate that silver ions inactivate enzymes by binding sulfhydryl (thiol) groups in amino acids and promote the release of iron with subsequent hydroxyl radical formation by an indirect mechanism likely mediated by reactive oxygen species. This is the first report investigating the global metabolic effects of silver in the context of a therapeutic application. We anticipate that the compounds presented here open a new treatment field with a high medical impact. PMID:20660682

  5. Silver coordination polymers for prevention of implant infection: thiol interaction, impact on respiratory chain enzymes, and hydroxyl radical induction.

    PubMed

    Gordon, Oliver; Vig Slenters, Tünde; Brunetto, Priscilla S; Villaruz, Amer E; Sturdevant, Daniel E; Otto, Michael; Landmann, Regine; Fromm, Katharina M

    2010-10-01

    Prosthetic joint replacements are used increasingly to alleviate pain and improve mobility of the progressively older and more obese population. Implant infection occurs in about 5% of patients and entails significant morbidity and high social costs. It is most often caused by staphylococci, which are introduced perioperatively. They are a source of prolonged seeding and difficult to treat due to antibiotic resistance; therefore, infection prevention by prosthesis coating with nonantibiotic-type anti-infective substances is indicated. A renewed interest in topically used silver has fostered development of silver nanoparticles, which, however, present a potential health hazard. Here we present new silver coordination polymer networks with tailored physical and chemical properties as nanostructured coatings on metallic implant substrates. These compounds exhibited strong biofilm sugar-independent bactericidal activity on in vitro-grown biofilms and prevented murine Staphylococcus epidermidis implant infection in vivo with slow release of silver ions and limited transient leukocyte cytotoxicity. Furthermore, we describe the biochemical and molecular mechanisms of silver ion action by gene screening and by targeting cell metabolism of S. epidermidis at different levels. We demonstrate that silver ions inactivate enzymes by binding sulfhydryl (thiol) groups in amino acids and promote the release of iron with subsequent hydroxyl radical formation by an indirect mechanism likely mediated by reactive oxygen species. This is the first report investigating the global metabolic effects of silver in the context of a therapeutic application. We anticipate that the compounds presented here open a new treatment field with a high medical impact.

  6. Laboratory investigations of the hydroxyl radical-initiated oxidation of atmospheric volatile organic compounds

    NASA Astrophysics Data System (ADS)

    Vimal, Deepali

    The hydroxyl radical (OH) is one of the most important oxidants in the atmosphere, because reaction with OH is the dominant atmospheric fate of most trace atmospheric species. OH is intimately involved in a complex non-linear photochemical pathway involving anthropogenic and biogenic emissions of volatile organic compounds (VOCs) and nitrogen oxides that are emitted from vehicular exhaust and industrial emissions. This chemistry generates secondary tropospheric ozone which is an important greenhouse gas as well as a component of photochemical smog. In addition, this chemistry leads to the formation of secondary organic aerosols in the atmosphere which have implications for public health and climate change. The focus of this dissertation is to improve our understanding of this complex chemistry by investigating the rate-limiting elementary reactions which are part of the OH-initiated oxidation of important VOCs. Experimental (discharge flow technique coupled with resonance fluorescence and laser induced fluorescence) and theoretical studies (Density Functional Theory computations) of the kinetics of three atmospheric VOCs, acetic acid, 1,3-butadiene and methyl ethyl ketone are discussed. The acetic acid and OH reaction has been thought to undergo a hydrogen-bonded complex mediated pathway instead of a direct one leading to faster rate constants at lower temperature. Our results for the experimental investigation between 263-373 K and pressures of 2-5 Torr for the gas phase reaction of acetic acid with OH confirm the complex mediated reaction mechanism and indicate that acetic acid can play an important role especially in the oxidative chemistry of upper troposphere. The 1,3-butadiene and OH reaction is thought to undergo electrophilicaddition by OH which could display a complex pressure dependence similar to isoprene and 232-butenol as noted earlier in this laboratory. However, our results for the kinetics of the reaction between 273-423 K and a pressure range of 1

  7. Study on superoxide and hydroxyl radicals generated in indirect electrochemical oxidation by chemiluminescence and UV-Visible spectra.

    PubMed

    Zhang, Bo-Tao; Zhao, Li-Xia; Lin, Jin-Ming

    2008-01-01

    The generation and transformation of radicals on the cathode of indirect electrochemical oxidation were studied by chemiluminescence (CL) and UV-Visible spectra in the reactor with a salt bridge that connected the separated chambers. The CL intensity of 4 x 10(-9) mol/L luminol on the cathode with bubbling oxygen was about seven times that of the intensity without it, which was because of the generation of reactive oxygen species (ROS). The existence of ROS, especially the generation of the superoxide radical, could be affirmed by the fact that the CL intensity of 4 x 10(-9) mol/L 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin-3-one with bubbling oxygen was about four times that of the intensity without it. However, there was no chemiluminescence on the anode under the same condition. The change in the UV-Visible spectra of nitro blue tetrazolium and N,N-dimethyl-4-nitrosoaniline at the cathode chamber affirmed the transformation from oxygen to superoxide and hydroxyl radicals. The mechanism of the superoxide and hydroxyl radical generation and transformation on the cathode was discussed with the help of the experimental results and relative references.

  8. The effectiveness of clove extracts in the inhibition of hydroxyl radical oxidation-induced structural and rheological changes in porcine myofibrillar protein.

    PubMed

    Chen, Hongsheng; Diao, Jingjing; Li, Yuanyuan; Chen, Qian; Kong, Baohua

    2016-01-01

    Oxidation is a major cause of protein quality deterioration during the storage and processing of food. This study investigated the effects of clove extract (CE) on structural and rheological changes in porcine longissimus myofibrillar proteins (MP) and the effects of oxidizing radicals produced by a Fenton reaction system (FRS). Increased oxidation time was accompanied by increased carbonyl content, reduced Ca-ATPase activity, decreased enthalpy of denaturation, decreased thermal transition temperatures (P<0.05), and increased protein susceptibility to thermal aggregation. The addition of CE significantly inhibited carbonyl formation (P<0.05), enhanced solubility and thermal stability, and improved the gel formation ability (storage modulus, loss modulus) of MP. The protective effect of CE on protein denaturation was demonstrated by its efficacy in maintaining Ca-ATPase activity and decreasing the degree of protein aggregation. Overall, the hydroxyl radical-induced loss of the structural and functional properties of MP was significantly reduced by the presence of CE.

  9. Acute neurogenic airway plasma exudation and edema induced by inhaled wood smoke in guinea pigs: role of tachykinins and hydroxyl radical.

    PubMed

    Lin, Y S; Kou, Y R

    2000-04-07

    We studied the mechanisms underlying the wood smoke-induced acute airway injury in 120 anaesthetized guinea pigs. Five minutes after airway exposure, various doses of wood smoke produced a dose-dependent increase in Evans blue dye contents at all airway levels measured. Additionally, inhaled wood smoke produced submucosal edema of the trachea and bronchus, and peribronchial edema. These acute airway responses were nearly abolished by pretreatment with CP-96,345 alone [a tachykinin NK(1) receptor antagonist; (2S, 3S)-cis-2-(diphenylmethyl)-N-((2-methoxyphenyl)-methyl)-1-azabicyc lo( 2.2.2.)-octan-3-amine] or with a combination of CP-96,345 and dimethylthiourea (a hydroxyl radical scavenger), and were attenuated by pretreatment with dimethylthiourea alone, yet were not affected by pretreatment with SR-48,968 [a tachykinin NK(2) receptor antagonist; (S)-N-methyl-N(4-(4-acetylamino-4-phenylpiperidino)-2-(3, 4-dichlorophenyl)-butyl)benzamide], with a combination of CP-96,344 and SR-48,965 (inactive enantiomers), with MK-886 [a leukotriene biosynthesis inhibitor; L-663, 536(3-(1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl)-2, 2-dimethylpropanoic acid], with indomethacin (a cyclooxygenase inhibitor), or with N(G)-nitro-L-arginine methyl ester (a nitric oxide (NO) synthase inhibitor). The activity of airway neutral endopeptidase (an enzyme for tachykinin degradation) was not influenced by wood smoke at 5-min post-exposure. We conclude that both endogenous tachykinins and hydroxyl radical play an important role in producing smoke-induced acute airway plasma exudation and airway edema in guinea pigs. The contribution of tachykinins to these neurogenic responses is mediated via the activation of tachykinin NK(1) receptors and partly via a hydroxyl radical mechanism, and is not associated with inactivation of neutral endopeptidase.

  10. Effect of pH and oxalate on hydroquinone-derived hydroxyl radical formation during brown rot wood degradation.

    PubMed

    Varela, Elisa; Tien, Ming

    2003-10-01

    The redox cycle of 2,5-dimethoxybenzoquinone (2,5-DMBQ) is proposed as a source of reducing equivalent for the regeneration of Fe2+ and H2O2 in brown rot fungal decay of wood. Oxalate has also been proposed to be the physiological iron reductant. We characterized the effect of pH and oxalate on the 2,5-DMBQ-driven Fenton chemistry and on Fe3+ reduction and oxidation. Hydroxyl radical formation was assessed by lipid peroxidation. We found that hydroquinone (2,5-DMHQ) is very stable in the absence of iron at pH 2 to 4, the pH of degraded wood. 2,5-DMHQ readily reduces Fe3+ at a rate constant of 4.5 x 10(3) M(-1)s(-1) at pH 4.0. Fe2+ is also very stable at a low pH. H2O2 generation results from the autoxidation of the semiquinone radical and was observed only when 2,5-DMHQ was incubated with Fe3+. Consistent with this conclusion, lipid peroxidation occurred only in incubation mixtures containing both 2,5-DMHQ and Fe3+. Catalase and hydroxyl radical scavengers were effective inhibitors of lipid peroxidation, whereas superoxide dismutase caused no inhibition. At a low concentration of oxalate (50 micro M), ferric ion reduction and lipid peroxidation are enhanced. Thus, the enhancement of both ferric ion reduction and lipid peroxidation may be due to oxalate increasing the solubility of the ferric ion. Increasing the oxalate concentration such that the oxalate/ferric ion ratio favored formation of the 2:1 and 3:1 complexes resulted in inhibition of iron reduction and lipid peroxidation. Our results confirm that hydroxyl radical formation occurs via the 2,5-DMBQ redox cycle.

  11. Vascular leakage induced by exposure to arsenic via increased production of NO, hydroxyl radical and peroxynitrite.

    PubMed

    Chen, Shih-Chieh; Chen, Wei-Chi

    2008-04-01

    Previous studies have shown that in situ exposure to arsenic induced increased vascular leakage. However, the underlying mechanism remains unclear. Reactive nitrogen and oxygen species such as nitric oxide (NO) and hydroxyl radical (OH(-)) are known to affect vascular permeability. Therefore, the goal of our present studies is to investigate the functional impact of the generation of NO or OH(-) on arsenic-induced vascular leakage. Vascular permeability changes were evaluated by means of Evans blue (EB) assay. Rats were anesthetized and intravenously injected with EB. Permeability changes were induced in back skin by intradermal injections of sodium arsenite mixed with NOS inhibitor: N(omega)-Nitro-L-arginine methyl ester (L-NAME) or aminoguanidine (AG) and OH(-) scavenger: 1,3 Dimethyl-2 thiourea (DMTU). Experiments were also performed to determine whether DMTU mixed with L-NAME would further inhibit arsenic-induced vascular leakage as compared with attenuation effects by either DMTU or L-NAME. One hour after administration, EB accumulated in the skin was extracted and quantified. Both L-NAME (0.02, 0.1 and 0.5 micromol/site) and DMTU (0.05, 0.2 and 1.2 micromol/site) inhibited the increase in vascular leakage induced by arsenite. However, only high dose (1 micromol/site) of AG significantly attenuated arsenite-induced vascular leakage. In contrast, neither D-NAME (0.02, 0.1 and 0.5 micromol/site) nor AG (0.04 and 0.2 micromol/site) attenuated increased vascular leakage by arsenic. DMTU mixed with L-NAME caused no further inhibition of arsenic-induced vascular leakage by either DMTU or L-NAME. The techniques of India ink and immunostaining were used to demonstrate both vascular labeling and nitrotyrosine staining in tissue treated with arsenic. L-NAME apparently reduced the density of leaky vessels and the levels of peroxynitrite staining induced by arsenite. These results suggest that NO, OH(-) and peroxynitrite play a role in increased vascular permeability

  12. Formation of hydroxyl radical from San Joaquin Valley particles extracted in a cell-free solution

    NASA Astrophysics Data System (ADS)

    Shen, H.; Anastasio, C.

    2011-06-01

    Previous studies have suggested that the adverse health effects from ambient particulate matter (PM) are linked to the formation of reactive oxygen species (ROS) by PM. While hydroxyl radical (•OH) is the most reactive of the ROS species, there are few quantitative studies of •OH generation from PM. Here we report on •OH formation from PM collected at an urban (Fresno) and rural (Westside) site in the San Joaquin Valley (SJV) of California. We quantified •OH in PM extracts using a cell-free, phosphate-buffered saline (PBS) solution with or without 50 μM ascorbate (Asc). The results show that generally the urban Fresno PM generates much more •OH than the rural Westside PM. The presence of Asc at a physiologically relevant concentration in the extraction solution greatly enhances •OH formation from all the samples. Fine PM (PM2.5) generally makes more •OH than the corresponding coarse PM (PMcf, i.e., 2.5 to 10 μm) normalized by air volume collected, while the coarse PM typically generates more •OH normalized by PM mass. •OH production by SJV PM is reduced on average by (97 ± 6) % when the transition metal chelator desferoxamine (DSF) is added to the extraction solution, indicating a dominant role of transition metals. By measuring calibration curves of •OH generation from copper and iron, and quantifying copper and iron concentrations in our particle extracts, we find that PBS-soluble copper is primarily responsible for •OH production by the SJV PM, while iron often makes a significant contribution. Extrapolating our results to expected burdens of PM-derived •OH in human lung lining fluid suggests that typical daily PM exposures in the San Joaquin Valley are unlikely to result in a high amount of pulmonary •OH, although high PM events could produce much higher levels of •OH, which might lead to cytotoxicity.

  13. Photochemical formation of hydroxyl radical from effluent organic matter: role of composition.

    PubMed

    Lee, Eunkyung; Glover, Caitlin M; Rosario-Ortiz, Fernando L

    2013-01-01

    The photochemical formation of hydroxyl radical (HO(•)) from effluent organic matter (EfOM) depends upon the chemical properties of this heterogeneous mixture. In this study, two EfOM samples collected from wastewater treatment plants (WWTP A and B) were fractionated by both hydrophobicity (bulk and non-humic) and apparent molecular weight (AMW). The apparent quantum yield for HO(•) formation (ΦHO(•)) and the maximum fluorescence quantum yield (ΦF) were subsequently measured for each subfraction. The formation rates of HO(•) (considering only the hydrogen-peroxide-independent pathways) for the bulk waters were 4.8 × 10(-10) and 9.6 × 10(-11) M s(-1) for WWTP A and B, respectively. For the AMW fractions, the values of ΦHO(•) increased as the AMW of the material decreased. For the WWTP A sample, the ΦHO(•) increased from 2.54 × 10(-4) (bulk water) to 6.29 × 10(-4) for the <1 kDa fraction, and for the WWTP B sample, the value of ΦHO(•) increased from 6.50 × 10(-5) for bulk water to 3.45 × 10(-4) for the <1 kDa fraction. In the case of fluorescence, the values of ΦF ranged from 2.37 × 10(-4) (bulk water) to 3.48 × 10(-4) (<1 kDa fraction) for WWTP A and 3.19 × 10(-4) (bulk water) to 5.75 × 10(-4) (<1 kDa fraction) for WWTP B. There was a linear correlation between ΦHO(•) and ΦF, suggesting that different photophysical processes occur in the chemical components of the fractions. Understanding the formation of HO(•) from EfOM is essential for understanding wastewater-impacted aquatic systems because these results influence the photochemical degradation and mineralization of trace organic contaminants.

  14. Secondary Organic Aerosol (SOA) formation from hydroxyl radical oxidation and ozonolysis of monoterpenes

    NASA Astrophysics Data System (ADS)

    Zhao, D. F.; Kaminski, M.; Schlag, P.; Fuchs, H.; Acir, I.-H.; Bohn, B.; Häseler, R.; Kiendler-Scharr, A.; Rohrer, F.; Tillmann, R.; Wang, M. J.; Wegener, R.; Wildt, J.; Wahner, A.; Mentel, T. F.

    2014-05-01

    Oxidation by hydroxyl radical (OH) and ozonolysis are the two major pathways of daytime biogenic volatile organic compounds (VOCs) oxidation and secondary organic aerosol (SOA) formation. In this study, we investigated the particle formation of several common monoterpenes (α-pinene, β-pinene, and limonene) by OH dominated oxidation, which has seldom been investigated. OH oxidation experiments were carried out in the SAPHIR chamber in Jülich, Germany, at low NOx (0.01-1 ppbV) and low ozone (O3) concentration. OH concentration and OH reactivity were measured directly so that the overall reaction rates of organic compounds with OH were quantified. Multi-generation reaction process, particle growth, new particle formation, particle yield, and chemical composition were analyzed and compared with that of monoterpene ozonolysis. Multi-generation products were found to be important in OH dominated SOA formation. The relative role of functionalization and fragmentation in the reaction process of OH oxidation was analyzed by examining the particle mass and the particle size as a function of OH dose. We developed a novel method which quantitatively links particle growth to the reaction of OH with organics in a reaction system. This method was also used to analyze the evolution of functionalization and fragmentation of organics in the particle formation by OH oxidation. It shows that functionalization of organics was dominant in the beginning of the reaction (within two lifetimes of the monoterpene) and fragmentation started to be dominant after that. We compared particle formation from OH oxidation with that from pure ozonolysis. In individual experiments, growth rates of the particle size did not necessarily correlate with the reaction rate of monoterpene with OH and O3. Comparing the size growth rates at the similar reaction rates of monoterpene with OH or O3 indicates that generally, OH oxidation and ozonolysis had similar efficiency in particle growth. The SOA yield of

  15. Secondary organic aerosol formation from hydroxyl radical oxidation and ozonolysis of monoterpenes

    NASA Astrophysics Data System (ADS)

    Zhao, D. F.; Kaminski, M.; Schlag, P.; Fuchs, H.; Acir, I.-H.; Bohn, B.; Häseler, R.; Kiendler-Scharr, A.; Rohrer, F.; Tillmann, R.; Wang, M. J.; Wegener, R.; Wildt, J.; Wahner, A.; Mentel, Th. F.

    2015-01-01

    Oxidation by hydroxyl radical (OH) and ozonolysis are the two major pathways of daytime biogenic volatile organic compound (BVOC) oxidation and secondary organic aerosol (SOA) formation. In this study, we investigated the particle formation of several common monoterpenes (α-pinene, β-pinene and limonene) by OH-dominated oxidation, which has seldom been investigated. OH oxidation experiments were carried out in the SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction) chamber in Jülich, Germany, at low NOx (0.01 ~ 1 ppbV) and low ozone (O3) concentration (< 20 ppbV). OH concentration and total OH reactivity (kOH) were measured directly, and through this the overall reaction rate of total organics with OH in each reaction system was quantified. Multi-generation reaction process, particle growth, new particle formation (NPF), particle yield and chemical composition were analyzed and compared with that of monoterpene ozonolysis. Multi-generation products were found to be important in OH-dominated SOA formation. The relative role of functionalization and fragmentation in the reaction process of OH oxidation was analyzed by examining the particle mass and the particle size as a function of OH dose. We developed a novel method which quantitatively links particle growth to the reaction rate of OH with total organics in a reaction system. This method was also used to analyze the evolution of functionalization and fragmentation of organics in the particle formation by OH oxidation. It shows that functionalization of organics was dominant in the beginning of the reaction (within two lifetimes of the monoterpene) and fragmentation started to play an important role after that. We compared particle formation from OH oxidation with that from pure ozonolysis. In individual experiments, growth rates of the particle size did not necessarily correlate with the reaction rate of monoterpene with OH and O3. Comparing the size growth rates at the similar reaction rates

  16. Mechanisms of hydroxyl radical production from abiotic oxidation of pyrite under acidic conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Yuan, Songhu; Liao, Peng

    2016-01-01

    Hydroxyl radicals (radOH) produced from pyrite oxidation by O2 have been recognized, but mechanisms regarding the production under anoxic and oxic conditions are not well understood. In this study, the mechanisms of radOH production from pyrite oxidation under anoxic and oxic conditions were explored using benzoic acid (BA) as an radOH probe. Batch experiments were conducted at pH 2.6 to explore radOH production under anoxic and oxic conditions. The cumulative radOH concentrations produced under anoxic and oxic conditions increased linearly to 7.5 and 52.2 μM, respectively within 10 h at 10 g/L pyrite. Under anoxic conditions, radOH was produced from the oxidation of H2O on the sulfur-deficient sites on pyrite surface, showing an increased production with the increase of pyrite surface exposure due to oxidation. Under oxic conditions, the formation of radOH proceeds predominantly via the two-electron reduction of O2 on pyrite surface along with a minor contribution from the oxidation of H2O on surface sulfur-defects and the reactions of Fe2+/sulfur intermediates with O2. For both O2 reduction and H2O oxidation on the surface sulfur-defects, H2O2 was the predominant intermediate, which subsequently transformed to radOH through Fenton mechanism. The radOH produced had a significant impact on the transformation of contaminants in the environment. Anoxic pyrite suspensions oxidized 13.9% As(III) (C0 = 6.67 μM) and 17.6% sulfanilamide (C0 = 2.91 μM) within 10 h at pH 2.6 and 10 g/L pyrite, while oxic pyrite suspensions improved the oxidation percentages to 55.4% for As(III) and 51.9% for sulfanilamide. The ratios of anoxic to oxic oxidation are consistent with the relative contribution of surface sulfur-defects to radOH production. However, Fe2+ produced from pyrite oxidation competed with the contaminants for radOH, which is of particular significance with the increase of time in a static environment. We conclude that radOH can be produced from abiotic oxidation of

  17. Secondary Organic Aerosol (SOA) Formation from Hydroxyl Radical Oxidation and Ozonolysis of Monoterpenes

    NASA Astrophysics Data System (ADS)

    Zhao, Defeng; Kaminski, Martin; Schlag, Patrick; Fuchs, Hendrik; Acir, Ismail-Hakki; Bohn, Birger; Haeseler, Rolf; Kiendler-Scharr, Astrid; Rohrer, Franz; Tillmann, Ralf; Wang, Mingjin; Wegner, Robert; Wahner, Andreas; Mentel, Thomas

    2014-05-01

    Hydroxyl radical (OH) oxidation and ozonolysis are the two major pathways of daytime biogenic volatile organic compounds (VOCs) oxidation and secondary organic aerosol (SOA) formation. The pure OH oxidation of monoterpenes, an important biogenic VOC class, has seldom been investigated. In order to elucidate the importance of the reaction pathyways of the OH oxidation and ozonolysis and their roles in particle formation and growth, we investigated the particle formation of several common monoterpenes (alpha-pinene, beta-pinene, and limonene) in the large atmosphere simulation chamber SAPHIR in Juelich, Germany. The experiments were conducted for both OH dominant and pure ozonolysis case (in the presence of CO as OH scavenger) at ambient relevant conditions (low OA, low VOC and low NOx concentration). OH and ozone (O3) concentrations were measured so that the oxidation rates of OH and O3 with precursors were quantified. The particle formation and growth, aerosol yield, multi-generation reaction process and aerosol composition were analyzed. Pure ozonolysis generated a large amount of particles indicating ozonolysis plays an important role in particle formation as well as OH oxidation. In individual experiments, particle growth rates did not necessarily correlate with OH or O3 oxidation rates. However, comparing the growth rates at similar OH or O3 oxidation rates shows that generally, OH oxidation and ozonolysis have similar efficiency in particle growth. Multi-generation products are shown to be important in the OH oxidation experiment based on aerosol yield "growth curve" (Ng et al., 2006). The reaction process of OH oxidation experiments was analyzed as a function of OH dose to elucidate the role of functionalization and fragmentation. A novel analysis was developed to link the particle formation with the reaction with OH, which was also used to examine the role of functionalization and fragmentation in the particle formation by OH oxidation. These analyses show

  18. Quantification of Hydroxyl Radical reactivity in the urban environment using the Comparative Reactivity Method (CRM)

    NASA Astrophysics Data System (ADS)

    Panchal, Rikesh; Monks, Paul

    2015-04-01

    Hydroxyl (OH) radicals play an important role in 'cleansing' the atmosphere of many pollutants such as, NOx, CH4 and various VOCs, through oxidation. To measure the reactivity of OH, both the sinks and sources of OH need to be quantified, and currently the overall sinks of OH seem not to be fully constrained. In order to measure the total rate loss of OH in an ambient air sample, all OH reactive species must be considered and their concentrations and reaction rate coefficients with OH known. Using the method pioneered by Sinha and Williams at the Max Plank Institute Mainz, the Comparative Reactivity Method (CRM) which directly quantifies total OH reactivity in ambient air without the need to consider the concentrations of individual species within the sample that can react with OH, has been developed and applied in a urban setting. The CRM measures the concentration of a reactive species that is present only in low concentrations in ambient air, in this case pyrrole, flowing through a reaction vessel and detected using Proton Transfer Reaction - Mass Spectrometry (PTR-MS). The poster will show a newly developed and tested PTR-TOF-MS system for CRM. The correction regime will be detailed to account for the influence of the varying humidity between ambient air and clean air on the pyrrole signal. Further, examination of the sensitivity dependence of the PTR-MS as a function of relative humidity and H3O+(H2O) (m/z=37) cluster ion allows the correction for the humidity variation, between the clean humid air entering the reaction vessel and ambient air will be shown. NO, present within ambient air, is also a potential interference and can cause recycling of OH, resulting in an overestimation of OH reactivity. Tests have been conducted on the effects of varying NO concentrations on OH reactivity and a correction factor determined for application to data when sampling ambient air. Finally, field tests in the urban environment at the University of Leicester will be shown

  19. Reaction between CH3O2 and BrO radicals: a new source of upper troposphere lower stratosphere hydroxyl radicals.

    PubMed

    Shallcross, Dudley E; Leather, Kimberley E; Bacak, Asan; Xiao, Ping; Lee, Edmond P F; Ng, Maggie; Mok, Daniel K W; Dyke, John M; Hossaini, Ryan; Chipperfield, Martyn P; Khan, M Anwar H; Percival, Carl J

    2015-05-14

    Over the last two decades it has emerged that measured hydroxyl radical levels in the upper troposphere are often underestimated by models, leading to the assertion that there are missing sources. Here we report laboratory studies of the kinetics and products of the reaction between CH3O2 and BrO radicals that shows that this could be an important new source of hydroxyl radicals:BrO + CH3O2 → products (1). The temperature dependent value in Arrhenius form of k(T) is k1 = (2.42–0.72+1.02) × 10–14 exp[(1617 ± 94)/T] cm3 molecule–1 s–1. In addition, CH2OO and HOBr are believed to be the major products. Global model results suggest that the decomposition of H2COO to form OH could lead to an enhancement in OH of up to 20% in mid-latitudes in the upper troposphere and in the lower stratosphere enhancements in OH of 2–9% are inferred from model integrations. In addition, reaction 1 aids conversion of BrO to HOBr and slows polar ozone loss in the lower stratosphere.

  20. Bactericidal Effect of Photolysis of H2O2 in Combination with Sonolysis of Water via Hydroxyl Radical Generation

    PubMed Central

    Sheng, Hong; Nakamura, Keisuke; Kanno, Taro; Sasaki, Keiichi; Niwano, Yoshimi

    2015-01-01

    The bactericidal effect of hydroxyl radical (·OH) generated by combination of photolysis of hydrogen peroxide (H2O2) and sonolysis of water was examined under the condition in which the yield of ·OH increased additively when H2O2 aqueous solution was concomitantly irradiated with laser and ultrasound. The suspension of Staphylococcus aureus mixed with the different concentrations of H2O2 was irradiated simultaneously with a laser light (wavelength: 405 nm, irradiance: 46 and 91 mW/cm2) and ultrasound (power: 30 w, frequency: 1.65 MHz) at 20 ± 1°C of the water bulk temperature for 2 min. The combination of laser and ultrasound irradiation significantly reduced the viable bacterial count in comparison with the laser irradiation of H2O2 alone. By contrast, the ultrasound irradiation alone exerted almost no bactericidal effect. These results suggested that the combination effect of photolysis of H2O2 and sonolysis of water on bactericidal activity was synergistic. A multi-way analysis of variance also revealed that the interaction of H2O2 concentration, laser power and ultrasound irradiation significantly affected the bactericidal activity. Since the result of oxidative DNA damage evaluation demonstrated that the combination of laser and ultrasound irradiation significantly induced oxidative damage of bacterial DNA in comparison with the laser irradiation of H2O2 alone, it was suggested that the combination effect of photolysis of H2O2 and sonolysis of water on bactericidal activity would be exerted via oxidative damage of cellular components such as DNA. PMID:26148024

  1. Analytical chemical kinetic investigation of the effects of oxygen, hydrogen, and hydroxyl radicals on hydrogen-air combustion

    NASA Technical Reports Server (NTRS)

    Carson, G. T., Jr.

    1974-01-01

    Quantitative values were computed which show the effects of the presence of small amounts of oxygen, hydrogen, and hydroxyl radicals on the finite-rate chemical kinetics of premixed hydrogen-air mixtures undergoing isobaric autoignition and combustion. The free radicals were considered to be initially present in hydrogen-air mixtures at equivalence ratios of 0.2, 0.6, 1.0, and 1.2. Initial mixture temperatures were 1100 K, 1200 K, and 1500 K, and pressures were 0.5, 1.0, 2.0, and 4.0 atm. Of the radicals investigated, atomic oxygen was found to be the most effective for reducing induction time, defined as the time to 5 percent of the total combustion temperature rise. The reaction time, the time between 5 percent and 95 percent of the temperature rise, is not decreased by the presence of free radicals in the initial hydrogen-air mixture. Fuel additives which yield free radicals might be used to effect a compact supersonic combustor design for efficient operation in an otherwise reaction-limited combustion regime.

  2. Immuno-chemistry of hydroxyl radical modified GAD-65: A possible role in experimental and human diabetes mellitus.

    PubMed

    Moinuddin; Ansari, Nadeem A; Shahab, Uzma; Habeeb, Safia; Ahmad, Saheem

    2015-10-01

    The repertoire of known auto-antigens is limited to a very small proportion of all human proteins, and the reason why only some proteins become auto-antigens is unclear. The 65 kDa isoform of the enzyme glutamic acid decarboxylase (GAD-65) is a major auto-antigen in type I diabetes, and in various neurological diseases. Most patients with type I diabetes (70-80%) have auto-antibodies against GAD-65, which often appear years before clinical onset of the autoimmune diabetes. Thus, the aim of the study is to focus on the immunogenicity of GAD65 and its reactive oxygen species (ROS) conformer in STZ-induced diabetic rats and on human diabetic patients. In the present study, GAD-65 was modified by hydroxyl radical following Fenton's reaction. The modifications in the structure of the GAD-65 are supported by UV-vis and fluorescence spectral studies. Immunogenicity of both native and hydroxyl radical modified GAD-65 (ROS-GAD-65) was studied in experimental rabbits and was confirmed by inducing type I diabetes in experimental male albino rats using streptozotocin (45 mg/kg). We found that ROS-GAD-65 was a better immunogen as compared to the native GAD-65. A considerable high binding to ROS-GAD-65 was observed as compared to native GAD-65 in both the serum antibodies from diabetes animal models and as well as in the serum samples of type I diabetes. Hydrogen peroxide under the exposure of UV light produces hydroxyl radical (·OH) which is most potent oxidant, and could cause protein damage (GAD-65) to the extent of generating neo-epitopes on the molecule, thus making it immunogenic.

  3. The Escherichia coli GTPase ObgE modulates hydroxyl radical levels in response to DNA replication fork arrest.

    PubMed

    Kint, Cyrielle I; Verstraeten, Natalie; Wens, Inez; Liebens, Veerle R; Hofkens, Johan; Versées, Wim; Fauvart, Maarten; Michiels, Jan

    2012-10-01

    Obg proteins are universally conserved GTP-binding proteins that are essential for viability in bacteria. Homologs in different organisms are involved in various cellular processes, including DNA replication. The goal of this study was to analyse the structure-function relationship of Escherichia coli ObgE with regard to DNA replication in general and sensitivity to stalled replication forks in particular. Defined C-terminal chromosomal deletion mutants of obgE were constructed and tested for sensitivity to the replication inhibitor hydroxyurea. The ObgE C-terminal domain was shown to be dispensable for normal growth of E.coli. However, a region within this domain is involved in the cellular response to replication fork stress. In addition, a mutant obgE over-expression library was constructed by error-prone PCR and screened for increased hydroxyurea sensitivity. ObgE proteins with substitutions L159Q, G163V, P168V, G216A or R237C, located within distinct domains of ObgE, display dominant-negative effects leading to hydroxyurea hypersensitivity when over-expressed. These effects are abolished in strains with a single deletion of the iron transporter TonB or combined deletions the toxin/antitoxin modules RelBE/MazEF, strains both of which have been shown to be involved in a pathway that stimulates hydroxyl radical formation following hydroxyurea treatment. Moreover, the observed dominant-negative effects are lost in the presence of the hydroxyl radical scavenger thiourea. Together, these results indicate involvement of hydroxyl radical toxicity in ObgE-mediated protection against replication fork stress.

  4. Predicting tropospheric ozone and hydroxyl radical in a global, three-dimensional, chemistry, transport, and deposition model

    SciTech Connect

    Atherton, C.S.

    1995-01-05

    Two of the most important chemically reactive tropospheric gases are ozone (O{sub 3}) and the hydroxyl radical (OH). Although ozone in the stratosphere is a necessary protector against the sun`s radiation, tropospheric ozone is actually a pollutant which damages materials and vegetation, acts as a respiratory irritant, and is a greenhouse gas. One of the two main sources of ozone in the troposphere is photochemical production. The photochemistry is initiated when hydrocarbons and carbon monoxide (CO) react with nitrogen oxides (NO{sub x} = NO + NO{sub 2}) in the presence of sunlight. Reaction with the hydroxyl radical, OH, is the main sink for many tropospheric gases. The hydroxyl radical is highly reactive and has a lifetime on the order of seconds. Its formation is initiated by the photolysis of tropospheric ozone. Tropospheric chemistry involves a complex, non-linear set of chemical reactions between atmospheric species that vary substantially in time and space. To model these and other species on a global scale requires the use of a global, three-dimensional chemistry, transport, and deposition (CTD) model. In this work, I developed two such three dimensional CTD models. The first model incorporated the chemistry necessary to model tropospheric ozone production from the reactions of nitrogen oxides with carbon monoxide (CO) and methane (CH{sub 4}). The second also included longer-lived alkane species and the biogenic hydrocarbon isoprene, which is emitted by growing plants and trees. The models` ability to predict a number of key variables (including the concentration of O{sub 3}, OH, and other species) were evaluated. Then, several scenarios were simulated to understand the change in the chemistry of the troposphere since preindustrial times and the role of anthropogenic NO{sub x} on present day conditions.

  5. Inhibitory activities of soluble and bound millet seed phenolics on free radicals and reactive oxygen species.

    PubMed

    Chandrasekara, Anoma; Shahidi, Fereidoon

    2011-01-12

    Oxidative stress, caused by reactive oxygen species (ROS), is responsible for modulating several pathological conditions and aging. Soluble and bound phenolic extracts of commonly consumed millets, namely, kodo, finger (Ravi), finger (local), foxtail, proso, little, and pearl, were investigated for their phenolic content and inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and ROS, namely, hydroxyl radical, peroxyl radical, hydrogen peroxide (H(2)O(2)), hypochlorous acid (HOCl), and singlet oxygen ((1)O(2)). Inhibition of DPPH and hydroxyl radicals was detrmined using electron paramagnetic resonance (EPR) spectroscopy. The peroxyl radical inhibitory activity was measured using the oxygen radical absorbance capacity (ORAC) assay. The scavenging of H(2)O(2), HOCl, and (1)O(2) was evaluated using colorimetric methods. The results were expressed as micromoles of ferulic acid equivalents (FAE) per gram of grain on a dry weight basis. In addition, major hydroxycinnamic acids were identified and quantified using high-performance liquid chromatography (HPLC) and HPLC-mass spectrometry (MS). All millet varieties displayed effective radical and ROS inhibition activities, which generally positively correlated with phenolic contents, except for hydroxyl radical. HPLC analysis revealed the presence of ferulic and p-coumaric acids as major hydroxycinnamic acids in phenolic extract and responsible for the observed effects. Bound extracts of millet contributed 38-99% to ROS scavenging, depending on the variety and the test system employed. Hence, bound phenolics must be included in the evaluation of the antioxidant activity of millets and other cereals.

  6. Hydroxyl radical-induced oxidation of a phenolic C-linked 2'-deoxyguanosine adduct yields a reactive catechol.

    PubMed

    Witham, Aaron A; Beach, Daniel G; Gabryelski, Wojciech; Manderville, Richard A

    2012-02-20

    Phenolic toxins stimulate oxidative stress and generate C-linked adducts at the C8-site of 2'-deoxyguanosine (dG). We previously reported that the C-linked adduct 8-(4″-hydroxyphenyl)-dG (p-PhOH-dG) undergoes oxidation in the presence of Na(2)IrCl(6) or horseradish peroxidase (HRP)/H(2)O(2) to generate polymeric adducts through phenoxyl radical production [ Weishar ( 2008 ) Org. Lett. 10 , 1839 - 1842 ]. We now report on reaction of p-PhOH-dG with two radical-generating systems, Cu(II)/H(2)O(2) or Fe(II)-EDTA/H(2)O(2), which were utilized to study the fate of the C-linked adduct in the presence of hydroxyl radical (HO(•)). The radical-generating systems facilitate (i) hydroxylation of the phenolic ring to afford the catechol adduct 8-(3″,4″-dihydroxyphenyl)-dG (3″,4″-DHPh-dG) and (ii) H-atom abstraction from the sugar moiety to generate the deglycosylated base p-PhOH-G. The ratios of 3″,4″-DHPh-dG to p-PhOH-G were ∼1 for Cu(II)/H(2)O(2) and ∼0.13 for Fe(II)-EDTA/H(2)O(2). The formation of 3″,4″-DHPh-dG was found to have important consequences in terms of reactivity. The catechol adduct has a lower oxidation potential than p-PhOH-dG and is sensitive to aqueous basic media, undergoing decomposition to generate a dicarboxylic acid derivative. In the presence of excess N-acetylcysteine (NAC), oxidation of 3″,4″-DHPh-dG produced mono-NAC and di-NAC conjugates. Our results imply that secondary oxidative pathways of phenolic-dG lesions are likely to contribute to toxicity.

  7. Temporal variation of hydroxyl radical generation and 8-hydroxy-2'-deoxyguanosine formation by coarse and fine particulate matter

    PubMed Central

    Shi, T; Knaapen, A; Begerow, J; Birmili, W; Borm, P; Schins, R

    2003-01-01

    Aims: To determine the induction of 8-hydroxy-2'-deoxyguanosine (8-OHdG) by fine (<2.5 µm) and coarse (10–2.5 µm) particulate matter (PM) sampled over time at one sampling location, and to relate the observed effects to the hydroxyl radical (•OH) generating activities and transition metal content of these samples, and to meteorological parameters. Methods: Weekly samples of coarse and fine PM were analysed for H2O2 dependent •OH formation using electron spin resonance (ESR) and formation of 8-OHdG in calf thymus DNA using an immuno-dotblot assay. Immunocytochemistry was used to determine 8-OHdG formation in A549 human epithelial lung cells. To determine temporal effects, samples from six weeks in summer and six weeks in autumn/winter were compared using ESR and the dotblot assay. Concentrations of leachable V, Cr, Fe, Ni, and Cu were determined by inductively coupled plasma mass spectrometry. Results: Both PM fractions elicited •OH generation as well as 8-OHdG formation in calf thymus DNA and in A549 cells. 8-OHdG formation in the naked DNA was significantly related to •OH generation, but not to metal concentrations except for copper. A significantly higher •OH generation was observed for coarse PM, but not fine PM collected during the autumn/winter season; this was not due to differences in sampled mass or metal content. Specific weather conditions under which increased •OH formation in the coarse mode was observed suggest that other, as yet unknown, anthropogenic components might affect the radical generating capacity of PM. Conclusions: Both coarse and fine PM are able to generate •OH, and induce formation of 8-OHdG. When considered at equal mass, •OH formation shows considerable variability with regard to the fraction of PM, as well as the sampling season. The toxicological implications of this heterogeneity in •OH formation by PM, as can be easily determined by ESR, need further investigation. PMID:12709515

  8. Oxidatively generated base damage to cellular DNA by hydroxyl radical and one-electron oxidants: similarities and differences.

    PubMed

    Cadet, Jean; Wagner, J Richard

    2014-09-01

    Hydroxyl radical (OH) and one-electron oxidants that may be endogenously formed through oxidative metabolism, phagocytosis, inflammation and pathological conditions constitute the main sources of oxidatively generated damage to cellular DNA. It is worth mentioning that exposure of cells to exogenous physical agents (UV light, high intensity UV laser, ionizing radiation) and chemicals may also induce oxidatively generated damage to DNA. Emphasis is placed in this short review article on the mechanistic aspects of OH and one-electron oxidant-mediated formation of single and more complex damage (tandem lesions, intra- and interstrand cross-links, DNA-protein cross-links) in cellular DNA arising from one radical hit. This concerns DNA modifications that have been accurately measured using suitable analytical methods such as high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry. Evidence is provided that OH and one-electron oxidants after generating neutral radicals and base radical cations respectively may partly induce common degradation pathways. In addition, selective oxidative reactions giving rise to specific degradation products of OH and one-electron oxidation reactions that can be used as representative biomarkers of these oxidants have been identified.

  9. Oh where OH where is Oh? Measuring the Elusive Hydroxyl Radical in the Atmosphere Using Laser-Induced Fluorescence

    NASA Astrophysics Data System (ADS)

    Stevens, Philip S.

    2016-06-01

    The hydroxyl radical (OH) plays a central role in the chemistry of the atmosphere. In addition to controlling the lifetimes of many trace gases important to issues of global climate change and stratospheric ozone depletion, the OH radical initiates the oxidation of carbon monoxide and volatile organic compounds which in the presence of nitrogen oxides can lead to the production of ground-level ozone and secondary organic aerosols, the primary components of photochemical smog. Accurate measurements of OH radical concentrations in the atmosphere can provide critical tests of our understanding of atmospheric chemistry and ground-level ozone production in urban and rural areas. Because of its high reactivity, mixing ratios of OH in the atmosphere are extremely low (typically less than 0.1 parts per trillion) and its chemical lifetime very short (less than 1 second). As a result, measurements of OH present a serious analytical challenge, especially on the timescale necessary to test our understanding of the fast photochemistry of the atmosphere. This presentation will describe the Indiana University laser-induced fluorescence instrument for the sensitive detection of OH radicals in the atmosphere, including recent results from several measurement campaigns in both urban and rural environments.

  10. Endogenous 3,4-dihydroxyphenylalanine and dopaquinone modifications on protein tyrosine: links to mitochondrially derived oxidative stress via hydroxyl radical.

    PubMed

    Zhang, Xu; Monroe, Matthew E; Chen, Baowei; Chin, Mark H; Heibeck, Tyler H; Schepmoes, Athena A; Yang, Feng; Petritis, Brianne O; Camp, David G; Pounds, Joel G; Jacobs, Jon M; Smith, Desmond J; Bigelow, Diana J; Smith, Richard D; Qian, Wei-Jun

    2010-06-01

    Oxidative modifications of protein tyrosines have been implicated in multiple human diseases. Among these modifications, elevations in levels of 3,4-dihydroxyphenylalanine (DOPA), a major product of hydroxyl radical addition to tyrosine, has been observed in a number of pathologies. Here we report the first proteome survey of endogenous site-specific modifications, i.e. DOPA and its further oxidation product dopaquinone in mouse brain and heart tissues. Results from LC-MS/MS analyses included 50 and 14 DOPA-modified tyrosine sites identified from brain and heart, respectively, whereas only a few nitrotyrosine-containing peptides, a more commonly studied marker of oxidative stress, were detectable, suggesting the much higher abundance for DOPA modification as compared with tyrosine nitration. Moreover, 20 and 12 dopaquinone-modified peptides were observed from brain and heart, respectively; nearly one-fourth of these peptides were also observed with DOPA modification on the same sites. For both tissues, these modifications are preferentially found in mitochondrial proteins with metal binding properties, consistent with metal-catalyzed hydroxyl radical formation from mitochondrial superoxide and hydrogen peroxide. These modifications also link to a number of mitochondrially associated and other signaling pathways. Furthermore, many of the modification sites were common sites of previously reported tyrosine phosphorylation, suggesting potential disruption of signaling pathways. Collectively, the results suggest that these modifications are linked with mitochondrially derived oxidative stress and may serve as sensitive markers for disease pathologies.

  11. Comparison of hydroxyl radical formation in aqueous solutions at different ultrasound frequencies and powers using the salicylic acid dosimeter.

    PubMed

    Milne, Louise; Stewart, Isobel; Bremner, David H

    2013-05-01

    Ultrasonic frequencies of 20kHz, 382kHz, 584kHz, 862kHz (and 998kHz) have been compared with regard to energy output and hydroxyl radical formation utilising the salicylic acid dosimeter. The 862kHz frequency inputs 6 times the number of Watts into water, as measured by calorimetry, with the other frequencies having roughly the same value under very similar conditions. A plausible explanation involving acoustic fountain formation is proposed although enhanced coupling between this frequency and water cannot be discounted. Using the salicylic acid dosimeter and inputting virtually the same Wattages it is established that 862kHz is around 10% more efficient at generating hydroxyl radicals than the 382kHz but both of these are far more effective than the other frequencies. Also, it is found that as temperature increases to 42°C then the total dihydroxybenzoic acid (Total DHBA) produced is virtually identical for 382kHz and 862kHz, though 582kHz is substantially lower, when the power levels are set at approximately 9W for all systems. An equivalent power level of 9W could not be obtained for the 998kHz transducer so a direct comparison could not be made in this instance. These results have implications for the optimum frequencies chosen for both Advanced Oxidation Processes (AOPs) and organic synthesis augmented by ultrasound.

  12. Stability and properties of the two-dimensional hexagonal boron nitride monolayer functionalized by hydroxyl (OH) radicals: a theoretical study.

    PubMed

    Wang, Hong-mei; Liu, Yue-jie; Wang, Hong-xia; Zhao, Jing-xiang; Cai, Qing-hai; Wang, Xuan-zhang

    2013-12-01

    Motivated by the great advance in graphene hydroxide--a versatile material with various applications--we performed density functional theory (DFT) calculations to study the functionalization of the two-dimensional hexagonal boron nitride (h-BN) sheet with hydroxyl (OH) radicals, which has been achieved experimentally recently. Particular attention was paid to searching for the most favorable site(s) for the adsorbed OH radicals on a h-BN sheet and addressing the roles of OH radical coverage on the stability and properties of functionalized h-BN sheet. The results indicate that, for an individual OH radica, the most stable configuration is that it is adsorbed on the B site of the h-BN surface with an adsorption energy of -0.88 eV and a magnetic moment of 1.00 μ(B). Upon adsorption of more than one OH radical on a h-BN sheet, however, these adsorbates prefer to adsorb in pairs on the B and its nearest N atoms from both sides of h-BN sheet without magnetic moment. An energy diagram of the average adsorption energy of OH radicals on h-BN sheet as a function of its coverage indicates that when the OH radical coverage reaches to 60 %, the functionalized h-BN sheet is the most stable among all studied configurations. More importantly, this configuration exhibits good thermal and dynamical stability at room temperature. Owing to the introduction of certain impurity levels, the band gap of h-BN sheet gradually decreases with increasing OH coverage, thereby enhancing its electrical conductivity.

  13. Maclurin protects against hydroxyl radical-induced damages to mesenchymal stem cells: antioxidant evaluation and mechanistic insight.

    PubMed

    Li, Xican; Gao, Yaoxiang; Li, Fei; Liang, Aifeng; Xu, Zhiming; Bai, Ye; Mai, Wenqiong; Han, Lu; Chen, Dongfeng

    2014-08-05

    Maclurin, an exceptional member of phytophenol family, was found to effectively protect against mesenchymal stem cells (MSCs) oxidative damage induced by hydroxyl radical (OH) at 62.1-310.5 μM. Antioxidant assays indicated that maclurin could efficiently protect DNA from OH-induced damage at 114.6-382.2 μM, and scavenge OH, DPPH (1,1-diphenyl-2-picrylhydrazyl radical), ABTS(+) (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid radical), and bind Cu(2+) (IC50 values were respectively 122.87 ± 10.14, 10.15 ± 0.85, 0.97 ± 0.07, and 133.95 ± 11.92 μM). HPLC-DAD and HPLC-ESI-MS/MS analyses of the end-product of maclurin reaction with DPPH clearly suggested that maclurin (m/z = 261.12 [M-H](-)) donated two hydrogen atoms to DPPH (m/z = 394.06 [M](+)) to form ortho-benzoquinone moiety (λmax = 364 nm; m/z = 259.06 [M-H](-), loss of m/z = 28) and DPPH2 molecule (m/z = 395.03, 396.01), via hydrogen atom transfer (HAT) or sequential electron (e) proton transfer (SEPT), not radical adduct formation (RAF) mechanisms. Therefore, we concluded that: (i) maclurin can effectively protect against OH-induced damages to DNA and MSCs, thereby it may have a therapeutic potential in prevention of many diseases or MSCs transplantation; (ii) a possible mechanism for maclurin to protect against oxidative damages is OH radical-scavenging; (iii) maclurin scavenges OH possibly through metal-chelating, and direct radical-scavenging which is mainly via HAT or SEPT mechanisms; and (iv) the protective and antioxidant effects of maclurin can be primarily attributed to ortho-dihydroxyl groups, and ultimately to the relative stability of the ortho-benzoquinone form.

  14. Study on the free radical scavenging activity of sea cucumber (Paracaudina chinens var.) gelatin hydrolysate

    NASA Astrophysics Data System (ADS)

    Zeng, Mingyong; Xiao, Feng; Zhao, Yuanhui; Liu, Zunying; Li, Bafang; Dong, Shiyuan

    2007-07-01

    Gelatin from the sea cucumber (Paracaudina chinens var.) was hydrolyzed by bromelain and the hydrolysate was found to have a high free radical scavenging activity. The hydrolysate was fractionated through an ultrafiltration membrane with 5 kDa molecular weight cutoff (MWCO). The portion (less than 5 kDa) was further separated by Sephadex G-25. The active peak was collected and assayed for free radical scavenging activity. The scavenging rates for superoxide anion radicals (O2·-) and hydroxyl radicals (·OH) of the fraction with the highest activity were 29.02% and 75.41%, respectively. A rabbit liver mitochondrial free radical damage model was adopted to study the free radical scavenging activity of the fraction. The results showed that the sea cucumber gelatin hydrolysate can prevent the damage of rabbit liver and mitochondria.

  15. The active titration method for measuring local hydroxyl radical concentration

    NASA Technical Reports Server (NTRS)

    Sprengnether, Michele; Prinn, Ronald G.

    1994-01-01

    We are developing a method for measuring ambient OH by monitoring its rate of reaction with a chemical species. Our technique involves the local, instantaneous release of a mixture of saturated cyclic hydrocarbons (titrants) and perfluorocarbons (dispersants). These species must not normally be present in ambient air above the part per trillion concentration. We then track the mixture downwind using a real-time portable ECD tracer instrument. We collect air samples in canisters every few minutes for roughly one hour. We then return to the laboratory and analyze our air samples to determine the ratios of the titrant to dispersant concentrations. The trends in these ratios give us the ambient OH concentration from the relation: dlnR/dt = -k(OH). A successful measurement of OH requires that the trends in these ratios be measureable. We must not perturb ambient OH concentrations. The titrant to dispersant ratio must be spatially invariant. Finally, heterogeneous reactions of our titrant and dispersant species must be negligible relative to the titrant reaction with OH. We have conducted laboratory studies of our ability to measure the titrant to dispersant ratios as a function of concentration down to the few part per trillion concentration. We have subsequently used these results in a gaussian puff model to estimate our expected uncertainty in a field measurement of OH. Our results indicate that under a range of atmospheric conditions we expect to be able to measure OH with a sensitivity of 3x10(exp 5) cm(exp -3). In our most optimistic scenarios, we obtain a sensitivity of 1x10(exp 5) cm(exp -3). These sensitivity values reflect our anticipated ability to measure the ratio trends. However, because we are also using a rate constant to obtain our (OH) from this ratio trend, our accuracy cannot be better than that of the rate constant, which we expect to be about 20 percent.

  16. Electrochemiluminescence sensors for scavengers of hydroxyl radical based on its annihilation in CdSe quantum dots film/peroxide system.

    PubMed

    Jiang, Hui; Ju, Huangxian

    2007-09-01

    This work elucidated the detailed electrochemiluminescence (ECL) process of the thioglycolic acid-capped CdSe quantum dots (QDs) film/peroxide aqueous system. The QDs were first electrochemically reduced to form electrons-injected QDs approximately -1.1 V, which then reduced hydrogen peroxide to produce OH* radical. The intermediate OH* radical was a key species for producing holes-injected QDs. The ECL emission with a peak at -1.114 V was demonstrated to come from the 1Se-1Sh transition emission. Using thiol compounds as the model molecules to annihilate the OH* radical, their quenching effects on ECL emission were studied. This effect led to a novel strategy for ECL sensing of the scavengers of hydroxyl radical. The detection results of thiol compounds showed high sensitivity, good precision, and acceptable accuracy, suggesting the promising application of the proposed method for quick detection of both scavengers and generators of hydroxyl radical in different fields.

  17. Hydroxyl radical formation resulting from the interaction of nickel complexes of L-histidine, glutathione or L-cysteine and hydrogen peroxide.

    PubMed

    Joshi, Seema; Husain, M M; Chandra, Ramesh; Hasan, S K; Srivastava, R C

    2005-01-01

    L-histidine, L-cysteine, reduced glutathione (GSH) and other bioligands, which are ubiquitously present in biological systems, are recognized as antioxidants. Studies have shown that nickel (II) complexed with these ligands catalyzes the disproportionation of H2O2, leading to the generation of hydroxyl radicals (OH radical). However, none of the studies could provide information regarding effective concentrations at which these ligands act either as pro-oxidant or antioxidant. Therefore, the observed paradoxical behaviour of biological antioxidants in nickel-induced oxidative response was evaluated. Benzoic acid (BA) is hydroxylated by OH radical to form highly fluorescent dihydroxy benzoate (OH-BA). We used this model to study the effect of nickel complexes of L-histidine, GSH or L-cysteine on the hydroxylation of BA. The concentration-dependent effect of L-histidine, GSH and L-cysteine, or nickel on the hydroxylation of BA was studied. The hydroxylation of BA was significantly enhanced up to 1:0.5 molar ratio (Ni:hist or GSH). However, beyond 1:0.5 molar ratios, histidine/GSH inhibited the hydroxylation and complete inhibition was observed at 1:1 molar ratios. Sorbitol and caffeic acid, considered as scavengers of hydroxyl radicals, inhibited nickel-induced hydroxylation of BA. The present study demonstrates paradoxical behaviour of these bioligands. They act as pro-oxidant at lower ligand ratios and as antioxidant at higher ligand ratios. The redox properties of nickel complexes with histidine, GSH or cysteine reported here may be crucial for the toxicity of nickel.

  18. Light-stimulated formation of hydrogen peroxide and hydroxyl radical in the presence of uroporphyrin and ascorbate

    SciTech Connect

    Bachowski, G.J.; Girotti, A.W. )

    1988-01-01

    Blue light irradiation of 2-deoxyribose (DOR) in the presence of uroporphyrin I (UP), ascorbate (AH-), trace iron, and phosphate buffer resulted in a strong stimulation of hydroxyl radical (OH.)-dependent oxidation of DOR. Photostimulated generation of H{sub 2}O{sub 2} was monitored after removal of residual AH- (i) by ascorbate oxidase treatment, or (ii) by anion exchange on mini-columns of DEAE-Sephadex. Irradiation of the above mixture produced a strong burst of H{sub 2}O{sub 2} which was intensified by desferrioxamine and suppressed by catalase or EDTA. The mechanism suggested by these observations is one in which photoreduction of UP to the radical anion initiates the formation of H{sub 2}O{sub 2}, which gives rise to OH. via Fenton chemistry. This is the first known investigation of H{sub 2}O{sub 2} fluxes in a Type I (free radical) photoreaction involving AH- as the electron donor.

  19. Efficiency of hydroxyl radical formation and phenol decomposition using UV light emitting diodes and H2O2.

    PubMed

    Vilhunen, Sari; Puton, Jarosław; Virkutyte, Jurate; Sillanpää, Mika

    2011-01-01

    A novel process combining hydrogen peroxide (H2O2) and radiation emitted by ultraviolet light emitting diodes (UV LEDs) has been investigated. The UV LEDs were used as UV-C light sources emitting radiation in the range 257-277 nm for decomposition of the model substance phenol in water. In addition, the effect of H2O2 to phenol molar ratio and initial phenol concentration was examined. Two parameters, the decomposition efficiency of phenol and characterization of hydroxyl radical (HO*) production from H2O2 when illuminated with UV radiation, were selected to provide detailed information regarding the performance of the UV LEDs in the treatment process. A new concept was introduced to characterize and describe the production of HO* radicals produced when photons were absorbed by H2O2 molecules. The phenol decomposition efficiency at the initial concentration of 100 mg/L was the most pronounced at the lowest emitted wavelength. A significant correlation was found between the phenol decomposition efficiency and the photons absorbed by H2O2 (i.e. formation of radicals).

  20. Experimental and theoretical investigations of the rate constant for the reaction of the hydroxyl radical with methyl ethyl ketone

    NASA Astrophysics Data System (ADS)

    Vimal, D.; Stevens, P. S.

    2007-12-01

    Methyl ethyl ketone (MEK) or 2-butanone is a high-volume industrial solvent with a production rate greater than 70 million lbs yr-1. It is also a photo-oxidation product of several volatile organic compounds (VOCs) in the atmosphere. MEK is removed from the atmosphere primarily by its reaction with hydroxyl (OH) radical. As a result, knowledge of the chemical mechanism and temperature dependence of this reaction is important as MEK may be transported to the upper troposphere and influence the chemistry of this region of the atmosphere. We present absolute measurements of the rate constant and the kinetic isotope effect for the reaction of MEK with OH radicals at low pressure and over the temperature range 263-388 K using a discharge-flow technique coupled with resonance fluorescence detection of OH radicals. Theoretical studies of the potential energy surface suggest that the reaction of MEK and OH proceeds by H-abstraction mediated by the formation of a 7- membered hydrogen-bonded complex. This mechanism is similar to that of several other atmospherically relevant oxygenated VOCs such as acetone, acetic acid and hydroxyacetone. The influence of the pre-reactive complex on the temperature dependence for this reaction will be discussed.

  1. Synergistic effect of thermal energy on bactericidal action of photolysis of H₂O₂ in relation to acceleration of hydroxyl radical generation.

    PubMed

    Shirato, Midori; Ikai, Hiroyo; Nakamura, Keisuke; Hayashi, Eisei; Kanno, Taro; Sasaki, Keiichi; Kohno, Masahiro; Niwano, Yoshimi

    2012-01-01

    The purpose of the present study is to evaluate the effect of thermal energy on the yield of and the bactericidal action of hydroxyl radical generated by photolysis of H(2)O(2). Different concentrations of H(2)O(2) (250, 500, 750, and 1,000 mM) were irradiated with light-emitting diodes (LEDs) at a wavelength of 400 ± 20 nm at 25°C to generate hydroxyl radical. The 500 mM H(2)O(2) was irradiated with the LEDs at different temperatures (25, 35, 45, and 55°C). Electron spin resonance spin trapping analysis showed that the yield of hydroxyl radicals increased with the temperature, as well as the concentration of H(2)O(2). Streptococcus mutans and Enterococcus faecalis were used in the bactericidal assay. The LED-light irradiation of the bacterial suspensions in 500 mM H(2)O(2) at 25°C could hardly kill the bacteria within 3 min, while the bactericidal effect was markedly enhanced with the temperature rise. For instance, a temperature increase to 55°C resulted in >99.999% reduction of viable counts of both bacterial species only within 1 min. The photolysis of 500 mM H(2)O(2) at 55°C could reduce the viable counts of bacteria more efficiently than did the photolysis of 1,000 mM H(2)O(2) at 25°C, although the yields of hydroxyl radical were almost the same under the both conditions. These findings suggest that the thermal energy accelerates the generation of hydroxyl radical by photolysis of H(2)O(2), which in turn results in a synergistic bactericidal effect of hydroxyl radical and thermal energy.

  2. Confirmation of hydroxyl radicals (•OH) generated in the presence of TiO2 supported on AC under microwave irradiation.

    PubMed

    Zhang, Zhaohong; Yu, Fengyang; Huang, Lirong; Jiatieli, Jianaerguli; Li, Yuanyuan; Song, Lijun; Yu, Ning; Dionysiou, Dionysios D

    2014-08-15

    In order to study the degradation mechanism of technology of microwave (MW) combined with TiO2 supported on activated carbon (TiO2/AC), the reactive oxygen species (ROS) was explored through oxidation of 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). Furthermore, 2,6-di-tert-butyl-4-methylphenol (BHT), Mannitol (MT) and Vitamin C (VC) were used as radical scavengers to confirm the generation of the hydroxyl radicals ((•)OH). In addition, the influence of some parameters such as TiO2 mass ratio content, irradiation time, material dose, DPCI concentration and MW power on the determination of (•)OH were examined. The results showed that the (•)OH could be generated under MW combined with loaded TiO2/AC. Also, anatase TiO2/AC can generate more (•)OH radicals than rutile TiO2/AC under MW irradiation. This work would provide new mechanistic insights on the enhanced degradation effect of organic pollutants in water using the supported TiO2/AC coupled with MW technology.

  3. Quantum-chemical modeling of gas-phase adsorption of the hydroxyl radical on IB metal clusters Me n ( n = 2-8)

    NASA Astrophysics Data System (ADS)

    Doroshenko, A. A.; Nechaev, I. V.; Vvedenskii, A. V.

    2014-09-01

    The structure of the most stable Me n clusters and Me n OH complexes (Me = Cu, Ag, Au; n = 2-8) was calculated using the density functional theory. The enthalpy and Gibbs energy of the interaction of OH· with metal clusters were calculated. It was shown that the hydroxyl radical is predominantly adsorbed into the bridge position on the metal IB clusters. During the adsorption of the hydroxyl radical, the frequency and intensity of the stretching vibrations of the O-H bond increased relative to the corresponding values for the isolated state; the frequency shift changed in the series Ag < Cu < Au.

  4. Cytokine toxicity in insulin-producing cells is mediated by nitro-oxidative stress-induced hydroxyl radical formation in mitochondria.

    PubMed

    Gurgul-Convey, Ewa; Mehmeti, Ilir; Lortz, Stephan; Lenzen, Sigurd

    2011-08-01

    Although nitric oxide (NO) and oxidative stress both contribute to proinflammatory cytokine toxicity in pancreatic β-cells during type 1 diabetes mellitus (T1DM) development, the interactions between NO and reactive oxygen species (ROS) in cytokine-mediated β-cell death have not been clarified. Exposure of insulin-producing RINm5F cells to IL-1β generated NO, while exposure to a combination of IL-1β, TNF-α, and IFN-γ, which simulates T1DM conditions, generated both NO and ROS. In theory, two reactions between NO and ROS are possible, one with the superoxide radical yielding peroxynitrite, and the other with hydrogen peroxide (H(2)O(2)) yielding hydroxyl radicals. Results of the present work exclude peroxynitrite involvement in cytokine toxicity to β-cells because its generation did not correlate with the toxic action of cytokines. On the other hand, we show that H(2)O(2), produced upon exposure of insulin-producing cell clones and primary rat islet cells to cytokines almost exclusively in the mitochondria, reacted in the presence of trace metal (Fe(++)) with NO forming highly toxic hydroxyl radicals, thus explaining the severe toxicity that causes apoptotic β-cell death. Expression of the H(2)O(2)-inactivating enzyme catalase in mitochondria protected against cytokine toxicity by preventing hydroxyl radical formation. We therefore conclude that proinflammatory cytokine-mediated β-cell death is due to nitro-oxidative stress-mediated hydroxyl radical formation in the mitochondria.

  5. In situ radiolysis time-resolved ESR studies of spin trapping by DMPO: Re-evalution of hydroxyl radical and hydrated electron trapping rates and spin adduct yields

    SciTech Connect

    Madden, K.P.; Taniguchi, Hitoshi

    1996-05-02

    The second-order rate constants for the reaction of 5, 5-dimethyl-1-pyrroline N-oxide (DMPO) with radiolytically produced hydroxyl radicals and hydrated electrons have been measured in aqueous solution by direct observation of spin adduct initial yield using time-resolved electron spin resonance. The rate constants are 2.8 x 10{sup 9} mol{sup -1} dm{sup 3} S{sup -1} for the DMPO-hydroxyl radical reaction and 3.2 x 10{sup 9} mol{sup -1} dm{sup 3} s{sup -1} for the reaction of DMPO and hydrated electron, using sodium formate and chloroacetic acid as competitive scavengers of the hydroxyl radical and hydrated electron, respectively. The hydrated electron-DMPO competition study determined the fraction of DMPO-H produced directly from radiolytically produced hydrogen atoms as 0.082 of the total DMPO-H yield, indicating that approximately half of the hydrogen atoms react with DMPO to produce non-aminoxyl products. The fraction of the total hydroxyl radical yield leading to DMPO-OH spin adduct was determined to be 0.94, using the bleach of 2,2,6,6-tetramethylpiperidone-N-oxyl by carbon dioxide radical anion as a reference standard. 36 refs., 8 figs., 1 tab.

  6. Measurement of hydroxyl radical-generated methane sulfinic acid by high-performance liquid chromatography and electrochemical detection.

    PubMed

    Jahnke, L S

    1999-05-01

    A liquid chromatographic (HPLC) method has been developed for direct quantitative determination of methane sulfinic acid (MSA) produced by hydroxyl radical oxidation of dimethyl sulfoxide. This method measures MSA directly by HPLC separation and electrochemical oxidation following rapid extraction from intact cells. MSA can be measured in tissue extracts at 0.04 nmol (equivalent to 2 microM). Using this technique, MSA production in paraquat-treated bean leaves is demonstrated. When compared with the widely used dye-binding technique, this method simplifies the preparation of the extract by eliminating two steps required in the dye-binding method: removal of interfering lipophilic compounds and the derivitization (color reaction) of the MSA.

  7. Generation mechanism of hydroxyl radical species and its lifetime prediction during the plasma-initiated ultraviolet (UV) photolysis

    PubMed Central

    Attri, Pankaj; Kim, Yong Hee; Park, Dae Hoon; Park, Ji Hoon; Hong, Young J.; Uhm, Han Sup; Kim, Kyoung-Nam; Fridman, Alexander; Choi, Eun Ha

    2015-01-01

    Through this work, we have elucidated the mechanism of hydroxyl radicals (OH•) generation and its life time measurements in biosolution. We observed that plasma-initiated ultraviolet (UV) photolysis were responsible for the continues generation of OH• species, that resulted in OH• to be major reactive species (RS) in the solution. The density and lifetime of OH• species acted inversely proportional to each other with increasing depth inside the solution. The cause of increased lifetime of OH• inside the solution is predicted using theoretical and semiempirical calculations. Further, to predict the mechanism of conversion of hydroxide ion (OH−) to OH• or H2O2 (hydrogen peroxide) and electron, we determined the current inside the solution of different pH. Additionally, we have investigated the critical criterion for OH• interaction on cancer cell inducing apoptosis under effective OH• exposure time. These studies are innovative in the field of plasma chemistry and medicine. PMID:25790968

  8. Generation mechanism of hydroxyl radical species and its lifetime prediction during the plasma-initiated ultraviolet (UV) photolysis

    NASA Astrophysics Data System (ADS)

    Attri, Pankaj; Kim, Yong Hee; Park, Dae Hoon; Park, Ji Hoon; Hong, Young J.; Uhm, Han Sup; Kim, Kyoung-Nam; Fridman, Alexander; Choi, Eun Ha

    2015-03-01

    Through this work, we have elucidated the mechanism of hydroxyl radicals (OH•) generation and its life time measurements in biosolution. We observed that plasma-initiated ultraviolet (UV) photolysis were responsible for the continues generation of OH• species, that resulted in OH• to be major reactive species (RS) in the solution. The density and lifetime of OH• species acted inversely proportional to each other with increasing depth inside the solution. The cause of increased lifetime of OH• inside the solution is predicted using theoretical and semiempirical calculations. Further, to predict the mechanism of conversion of hydroxide ion (OH-) to OH• or H2O2 (hydrogen peroxide) and electron, we determined the current inside the solution of different pH. Additionally, we have investigated the critical criterion for OH• interaction on cancer cell inducing apoptosis under effective OH• exposure time. These studies are innovative in the field of plasma chemistry and medicine.

  9. Neo-Epitopes Generated on Hydroxyl Radical Modified GlycatedIgG Have Role in Immunopathology of Diabetes Type 2

    PubMed Central

    Islam, Sidra; Mir, Abdul Rouf; Raghav, Alok; Khan, Farzana; Alam, Khursheed; Ali, Asif; Uddin, Moin

    2017-01-01

    Glycoxidation plays a crucial role in diabetes and its associated complications. Among the glycoxidation agents, methylglyoxal (MG) is known to have very highglycationpotential witha concomitant generation of reactive oxygen species (ROS) during its synthesis and degradation. The presentstudy probes the MG and ROSinduced structural damage to immunoglobulin G (IgG) and alterations in its immunogenicity in diabetes type 2 patients (T2DM). Human IgG was first glycated with MG followed by hydroxyl radical (OH•) modification. Glycoxidation mediated effects on IgG were evaluated by various physicochemical techniques likeultraviolet (UV) and fluorescence spectroscopy, 8-anilinonaphthalene-1-sulfonic acid (ANS) binding studies, carbonyl andfree sulfhydryl groups assay, matrix assisted laser desorption ionization mass spectrometry-time of flight (MALDI-TOF), red blood cell (RBC) haemolysis assay, Congored (CR) staining analysis and scanning electron microscopy (SEM). The results revealed hyperchromicityin UV, advanced glycation end product (AGE)specific and ANS fluorescence, quenching in tyrosine and tryptophan fluorescence intensity,enhanced carbonyl content,reduction in free sulfhydryl groups,pronounced shift in m/z value of IgGand decrease in antioxidant activity in RBC induced haemolysis assayupon glycoxidation. SEM and CRstaining assay showed highly altered surface morphology in glycoxidised sample as compared to the native. Enzyme linked immunosorbent assay (ELISA) and band shift assay were performed to assess the changes in immunogenicity of IgG upon glyoxidation and its role in T2DM. The serum antibodies derived from T2DM patients demonstrated strong affinity towards OH• treated MG glycatedIgG (OH•-MG-IgG) when compared to native IgG (N-IgG) or IgGs treated with MG alone (MG-IgG) or OH• alone (OH•-IgG). This study shows the cumulating effect of OH• on the glycation potential of MG. The results point towards the modification of IgG in diabetes patients

  10. Neo-Epitopes Generated on Hydroxyl Radical Modified GlycatedIgG Have Role in Immunopathology of Diabetes Type 2.

    PubMed

    Islam, Sidra; Mir, Abdul Rouf; Raghav, Alok; Khan, Farzana; Alam, Khursheed; Ali, Asif; Uddin, Moin

    2017-01-01

    Glycoxidation plays a crucial role in diabetes and its associated complications. Among the glycoxidation agents, methylglyoxal (MG) is known to have very highglycationpotential witha concomitant generation of reactive oxygen species (ROS) during its synthesis and degradation. The presentstudy probes the MG and ROSinduced structural damage to immunoglobulin G (IgG) and alterations in its immunogenicity in diabetes type 2 patients (T2DM). Human IgG was first glycated with MG followed by hydroxyl radical (OH•) modification. Glycoxidation mediated effects on IgG were evaluated by various physicochemical techniques likeultraviolet (UV) and fluorescence spectroscopy, 8-anilinonaphthalene-1-sulfonic acid (ANS) binding studies, carbonyl andfree sulfhydryl groups assay, matrix assisted laser desorption ionization mass spectrometry-time of flight (MALDI-TOF), red blood cell (RBC) haemolysis assay, Congored (CR) staining analysis and scanning electron microscopy (SEM). The results revealed hyperchromicityin UV, advanced glycation end product (AGE)specific and ANS fluorescence, quenching in tyrosine and tryptophan fluorescence intensity,enhanced carbonyl content,reduction in free sulfhydryl groups,pronounced shift in m/z value of IgGand decrease in antioxidant activity in RBC induced haemolysis assayupon glycoxidation. SEM and CRstaining assay showed highly altered surface morphology in glycoxidised sample as compared to the native. Enzyme linked immunosorbent assay (ELISA) and band shift assay were performed to assess the changes in immunogenicity of IgG upon glyoxidation and its role in T2DM. The serum antibodies derived from T2DM patients demonstrated strong affinity towards OH• treated MG glycatedIgG (OH•-MG-IgG) when compared to native IgG (N-IgG) or IgGs treated with MG alone (MG-IgG) or OH• alone (OH•-IgG). This study shows the cumulating effect of OH• on the glycation potential of MG. The results point towards the modification of IgG in diabetes patients

  11. Relationships between the structure of natural organic matter and its reactivity towards molecular ozone and hydroxyl radicals

    USGS Publications Warehouse

    Westerhoff, P.; Aiken, G.; Amy, G.; Debroux, J.

    1999-01-01

    Oxidation reaction rate parameters for molecular ozone (O3) and hydroxyl (HO) radicals with a variety of hydrophobic organic acids (HOAs) isolated from different geographic locations were determined from batch ozonation studies. Rate parameter values, obtained under equivalent dissolved organic carbon concentrations in both the presence and absence of non-NOM HO radical scavengers, varied as a function of NOM structure. First-order rate constants for O3 consumption (k(O3)) averaged 8.8 x 10-3 s-1, ranging from 3.9 x 10-3 s-1 for a groundwater HOA to > 16 x 10-3 s-1 for river HOAs with large terrestrial carbon inputs. The average second-order rate constant (k(HO,DOC) between HO radicals and NOM was 3.6 x 108 l (mol C)-1 s-1; a mass of 12 g C per mole C was used in all calculations. Specific ultraviolet absorbance (SUVA) at 254 or 280 nm of the HOAs correlated well (r > 0.9) with O3 consumption rate parameters, implying that organic ??-electrons strongly and selectively influence oxidative reactivity. HO radical reactions with NOM were less selective, although correlation between k(HO,DOC) and SUVA existed. Other physical-chemical properties of NOM, such as aromatic and aliphatic carbon content from 13C-NMR spectroscopy, proved less sensitive for predicting oxidation reactivity than SUVA. The implication of this study is that the structural nature of NOM varies temporally and spatially in a water source, and both the nature and amount of NOM will influence oxidation rates.

  12. Validation of a robust and sensitive method for detecting hydroxyl radical formation together with evoked neurotransmitter release in brain microdialysis.

    PubMed

    Freinbichler, Wolfhardt; Colivicchi, Maria A; Fattori, Manuela; Ballini, Chiara; Tipton, Keith F; Linert, Wolfgang; Della Corte, Laura

    2008-05-01

    Sodium terephthalate was shown to be a new robust and sensitive chemical trap for highly reactive oxygen species (hROS), which lacks the drawbacks of the salicylic acid method. Reaction of the almost non-fluorescent terephthalate (TA2-) with hydroxyl radicals or ferryl-oxo species resulted in the stoichiometric formation of the brilliant fluorophor, 2-hydroxyterephthalate (OH-TA). Neither hydrogen peroxide nor superoxide reacts in this system. This procedure was validated for determining hROS formation during microdialysis under in vivo conditions as well as by in vitro studies. The detection limit of OH-TA in microdialysis samples was 0.5 fmol/muL. Derivatization of samples with o-phthalaldehyde, for amino acid detection, had no effect on OH-TA fluorescence, which could easily be resolved from the amino acid derivatives by HPLC, allowing determination in a single chromatogram. Use of terephthalate in microdialysis experiments showed the neurotoxin kainate to evoke hROS formation in a dose-dependent manner. The presence of TA2- in the perfusion fluid did not affect basal or evoked release of aspartate, glutamate, taurine and GABA. Assessment of cell death 'ex vivo' showed TA2- to be non-toxic at concentrations up to 1 mM. The in vitro results in the Fenton system (Fe2+ + H2O2) indicate a mechanism whereby TA2- forms a primary complex with Fe2+ followed by an intramolecular hydroxylation accompanied by intramolecular electron transfer.

  13. A synchrotron-based hydroxyl radical footprinting analysis of amyloid fibrils and prefibrillar intermediates with residue-specific resolution.

    PubMed

    Klinger, Alexandra L; Kiselar, Janna; Ilchenko, Serguei; Komatsu, Hiroaki; Chance, Mark R; Axelsen, Paul H

    2014-12-16

    Structural models of the fibrils formed by the 40-residue amyloid-β (Aβ40) peptide in Alzheimer's disease typically consist of linear polypeptide segments, oriented approximately perpendicular to the long axis of the fibril, and joined together as parallel in-register β-sheets to form filaments. However, various models differ in the number of filaments that run the length of a fibril, and in the topological arrangement of these filaments. In addition to questions about the structure of Aβ40 monomers in fibrils, there are important unanswered questions about their structure in prefibrillar intermediates, which are of interest because they may represent the most neurotoxic form of Aβ40. To assess different models of fibril structure and to gain insight into the structure of prefibrillar intermediates, the relative solvent accessibility of amino acid residue side chains in fibrillar and prefibrillar Aβ40 preparations was characterized in solution by hydroxyl radical footprinting and structural mass spectrometry. A key to the application of this technology was the development of hydroxyl radical reactivity measures for individual side chains of Aβ40. Combined with mass-per-length measurements performed by dark-field electron microscopy, the results of this study are consistent with the core filament structure represented by two- and three-filament solid state nuclear magnetic resonance-based models of the Aβ40 fibril (such as 2LMN , 2LMO , 2LMP , and 2LMQ ), with minor refinements, but they are inconsistent with the more recently proposed 2M4J model. The results also demonstrate that individual Aβ40 fibrils exhibit structural heterogeneity or polymorphism, where regions of two-filament structure alternate with regions of three-filament structure. The footprinting approach utilized in this study will be valuable for characterizing various fibrillar and nonfibrillar forms of the Aβ peptide.

  14. Endogenous 3, 4- Dihydroxyphenylalanine and Dopaquinone Modifications on Protein Tyrosine: links to mitochondrially derived oxidative stress via hydroxyl radical

    SciTech Connect

    Zhang, Xu; Monroe, Matthew E.; Chen, Baowei; Chin, Mark H.; Heibeck, Tyler H.; Schepmoes, Athena A.; Yang, Feng; Petritis, Brianne O.; Camp, David G.; Pounds, Joel G.; Jacobs, Jon M.; Smith, Desmond J.; Bigelow, Diana J.; Smith, Richard D.; Qian, Weijun

    2010-06-02

    Oxidative modifications of protein tyrosines have been implicated in multiple human diseases. Among these modifications, elevations in levels of 3, 4-dihydroxyphenylalanine (DOPA), a major product of hydroxyl radical addition to tyrosine, has been observed in a number of pathologies. Here we report the first global proteome survey of endogenous site-specific modifications, i.e, DOPA and its further oxidation product dopaquinone (DQ) in mouse brain and heart tissues. Results from LC-MS/MS analyses included 203 and 71 DOPA-modified tyrosine sites identified from brain and heart, respectively, with a false discovery rate of ~1%; while only a few nitrotyrosine containing peptides, a more commonly studied marker of oxidative stress, were detectable, suggesting the much higher abundance for DOPA modification as compared with tyrosine nitration. Moreover, 57 and 29 DQ modified peptides were observed from brain and heart, respectively; nearly half of these peptides were also observed with DOPA modification on the same sites. For both tissues, these modifications are preferentially found in mitochondrial proteins with metal-binding properties, consistent with metal catalyzed hydroxyl radical formation from mitochondrial superoxide and hydrogen peroxide. These modifications also link to a number of mitochondria-associated and other signaling pathways. Furthermore, many of the modification sites were common sites of previously reported tyrosine phosphorylation suggesting potential disruption of signaling pathways. Structural aspects of DOPA-modified tyrosine sequences are distinct from those of nitrotyrosines suggesting that each type of modifications provides a marker for different in vivo reactive chemistries and can be used to predict sensitive protein targets. Collectively, the results suggest that these modifications are linked with mitochondrially-derived oxidative stress, and may serve as sensitive markers for disease pathologies.

  15. A Synchrotron-Based Hydroxyl Radical Footprinting Analysis of Amyloid Fibrils and Prefibrillar Intermediates with Residue-Specific Resolution

    SciTech Connect

    Klinger, Alexandra L.; Kiselar, Janna; Ilchenko, Serguei; Komatsu, Hiroaki; Chance, Mark R.; Axelsen, Paul H.

    2014-11-09

    The structural models of the fibrils formed by the 40-residue amyloid-β (Aβ40) peptide in Alzheimer’s disease typically consist of linear polypeptide segments, oriented approximately perpendicular to the long axis of the fibril, and joined together as parallel in-register β-sheets to form filaments. However, various models differ in the number of filaments that run the length of a fibril, and in the topological arrangement of these filaments. In addition to questions about the structure of Aβ40 monomers in fibrils, there are important unanswered questions about their structure in prefibrillar intermediates, which are of interest because they may represent the most neurotoxic form of Aβ40. To assess different models of fibril structure and to gain insight into the structure of prefibrillar intermediates, the relative solvent accessibility of amino acid residue side chains in fibrillar and prefibrillar Aβ40 preparations was characterized in solution by hydroxyl radical footprinting and structural mass spectrometry. A key to the application of this technology was the development of hydroxyl radical reactivity measures for individual side chains of Aβ40. When we combined mass-per-length measurements performed by dark-field electron microscopy, we determined that the results of our study were consistent with the core filament structure represented by two- and three-filament solid state nuclear magnetic resonance-based models of the Aβ40 fibril (such as 2LMN, 2LMO, 2LMP, and 2LMQ), with minor refinements, but they are inconsistent with the more recently proposed 2M4J model. Our results also demonstrate that individual Aβ40 fibrils exhibit structural heterogeneity or polymorphism, where regions of two-filament structure alternate with regions of three-filament structure. The footprinting approach utilized in this study will be valuable for characterizing various fibrillar and nonfibrillar forms of the Aβ peptide.

  16. A shock tube study of the reactions of the hydroxyl radical with combustion species

    SciTech Connect

    Cohen, N.; Koffend, J.B.

    1993-12-01

    To extend the semi-empirical techniques of Benson and coworkers, and to extend the database of reliable high temperature measurements of OH radicals with hydrocarbons and other fuels and their decomposition products, the authors undertook a research program with both experimental and computational tasks. The experimental goal was to design a procedure for measuring, at combustion temperatures, the reaction rate coefficients of OH radicals with fuels and other species of importance in combustion or propulsion systems. The computational effort was intended to refine the semi-empirical transition-state-theory procedures for extrapolating rate coefficients of reactions of OH with combustion species of interest, for predicting rate coefficients for species not studied in the laboratory, and to examine the ability of the theory to predict rate coefficients for different pathways in the case the reagent possessed more than one nonequivalent H atoms.

  17. A shock tube study of the reactions of the hydroxyl radical with combustion species and pollutants

    SciTech Connect

    Cohen, N.

    1992-08-01

    To extend the database of reliable high temperature measurements of OH radicals with hydrocarbons and other fuels and their decomposition products, we undertook, a research program with both experimental and computational tasks. The experimental goal was to design a procedure for measuring, at combustion temperatures, the reaction rate coefficients of OH radicals with fuels and other species of importance in combustion or propulsion systems. The computational effort was intended to refine the semi-empirical thermochemical kinetics/ transition-state-theory (TK-TST) procedures for extrapolating rate coefficients of reactions of OH with combustion species of interest, for predicting rate coefficients for species not studied in the laboratory, and to examine the ability of the theory to predict rate coefficients for different pathways in cases where the reagent possessed nonequivalent H atoms.

  18. Ozone degrades into hydroxyl radical under physiological conditions: a spin trapping study

    SciTech Connect

    Grimes, H.D.; Perkins, K.K.; Boss, W.F.

    1983-01-01

    Defining the reactants is a critical step towards elucidating the mechanism of ozone toxicity to biomembranes. To document ozone-induced HO x radicals, the spin trap 5,5-dimethyl-1-pyrroline-N-oxide was used and the resulting spin adduct was monitored with electron spin resonance spectroscopy. Chelexed potassium phosphate buffer a pH 7.2 and 7.8 was exposed to ozone by directing a stream of ozone over the surface for 60 seconds. Under these conditions, no HO x was detected. Using 0.5 x 10/sup -4/ molar caffeic acid in phosphate buffer, strong DMPO x OH electron spin resonance signals were obtained, indicating HO x production. High pH (7.8) enhanced signal strength. Furthermore, with sorbitol a net HO x signal loss of 28% was observed, while a carbon-centered sorbitol radical adduct appeared. Although HO x radicals were produced, no breakage of Daucus carota protoplast plasma membranes was observed nor were differences in membrane fluidity observed as determined by 5-doxyl stearic acid.

  19. LIF diagnostics of hydroxyl radical in a methanol containing atmospheric-pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Qian, Mu-Yang; Liu, San-Qiu; Pei, Xue-Kai; Lu, Xin-Pei; Zhang, Jia-Liang; Wang, De-Zhen

    2016-10-01

    In this paper, a pulsed-dc CH3OH/Ar plasma jet generated at atmospheric pressure is studied by laser-induced fluorescence (LIF) and optical emission spectroscopy (OES). A gas-liquid bubbler system is proposed to introduce the methanol vapor into the argon gas, and the CH3OH/Ar volume ratio is kept constant at about 0.1%. Discharge occurs in a 6-mm needle-to-ring gap in an atmospheric-pressure CH3OH/Ar mixture. The space-resolved distributions of OH LIF inside and outside the nozzle exhibit distinctly different behaviors. And, different production mechanisms of OH radicals in the needle-to-ring discharge gap and afterglow of plasma jet are discussed. Besides, the optical emission lines of carbonaceous species, such as CH, CN, and C2 radicals, are identified in the CH3OH/Ar plasma jet. Finally, the influences of operating parameters (applied voltage magnitude, pulse frequency, pulsewidth) on the OH radical density are also presented and analyzed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11465013 and 11375041), the Natural Science Foundation of Jiangxi Province, China (Grant Nos. 20151BAB212012 and 20161BAB201013), and the International Science and Technology Cooperation Program of China (Grant No. 2015DFA61800).

  20. Mechanism of hydroxyl radical generation from a silica surface: molecular orbital calculations.

    PubMed

    Narayanasamy, Jayakumar; Kubicki, James D

    2005-11-24

    The interaction of an H(2)O molecule with cluster models of fractured silica surfaces was studied by means of quantum mechanical calculations. Two clusters representing homolytic cleavage (triple bond Si(*) and triple bond SiO(*)) and two representing heterolytic cleavage (triple bond Si(+) and triple bond Si-O(-)) of silica surfaces were modeled. Vibrational frequencies of the reactants and products of these silica surfaces reacting with H(2)O have been calculated and compare favorably with experiment. Comparisons of the Gibbs free and potential energies for the model ionic and radical states were made, and the radical pair of sites was predicted to be more stable by approximately -70 to -85 kJ/mol, depending on the computational methodology. These calculations suggest that when silica is fractured in a vacuum homolytic cleavage is favored. Reaction pathways were investigated for these four model surface sites interacting with H(2)O. The reaction of H(2)O with triple bond SiO(*) was predicted to generate OH(*). Rate constants for these reactions were also calculated and predict a rapid equibrium for the reaction triple bond SiO(*) + H(2)O --> triple bond SiOH + OH(*). Stability of a finite number of triple bond SiO(*) sites at equilibrium in the above reaction with H(2)O was also predicted, which implies a long-term ability of silica surfaces to produce OH(*) radicals if the sites of the broken bonds do not repolymerize to form siloxane groups.

  1. Volatile organic compound conversion by ozone, hydroxyl radicals, and nitrate radicals in residential indoor air: Magnitudes and impacts of oxidant sources.

    PubMed

    Waring, Michael S; Wells, J Raymond

    2015-04-01

    Indoor chemistry may be initiated by reactions of ozone (O3), the hydroxyl radical (OH), or the nitrate radical (NO3) with volatile organic compounds (VOC). The principal indoor source of O3 is air exchange, while OH and NO3 formation are considered as primarily from O3 reactions with alkenes and nitrogen dioxide (NO2), respectively. Herein, we used time-averaged models for residences to predict O3, OH, and NO3 concentrations and their impacts on conversion of typical residential VOC profiles, within a Monte Carlo framework that varied inputs probabilistically. We accounted for established oxidant sources, as well as explored the importance of two newly realized indoor sources: (i) the photolysis of nitrous acid (HONO) indoors to generate OH and (ii) the reaction of stabilized Criegee intermediates (SCI) with NO2 to generate NO3. We found total VOC conversion to be dominated by reactions both with O3, which almost solely reacted with d-limonene, and also with OH, which reacted with d-limonene, other terpenes, alcohols, aldehydes, and aromatics. VOC oxidation rates increased with air exchange, outdoor O3, NO2 and d-limonene sources, and indoor photolysis rates; and they decreased with O3 deposition and nitric oxide (NO) sources. Photolysis was a strong OH formation mechanism for high NO, NO2, and HONO settings, but SCI/NO2 reactions weakly generated NO3 except for only a few cases.

  2. Volatile organic compound conversion by ozone, hydroxyl radicals, and nitrate radicals in residential indoor air: Magnitudes and impacts of oxidant sources

    PubMed Central

    Waring, Michael S.; Wells, J. Raymond

    2016-01-01

    Indoor chemistry may be initiated by reactions of ozone (O3), the hydroxyl radical (OH), or the nitrate radical (NO3) with volatile organic compounds (VOC). The principal indoor source of O3 is air exchange, while OH and NO3 formation are considered as primarily from O3 reactions with alkenes and nitrogen dioxide (NO2), respectively. Herein, we used time-averaged models for residences to predict O3, OH, and NO3 concentrations and their impacts on conversion of typical residential VOC profiles, within a Monte Carlo framework that varied inputs probabilistically. We accounted for established oxidant sources, as well as explored the importance of two newly realized indoor sources: (i) the photolysis of nitrous acid (HONO) indoors to generate OH and (ii) the reaction of stabilized Criegee intermediates (SCI) with NO2 to generate NO3. We found total VOC conversion to be dominated by reactions both with O3, which almost solely reacted with d-limonene, and also with OH, which reacted with d-limonene, other terpenes, alcohols, aldehydes, and aromatics. VOC oxidation rates increased with air exchange, outdoor O3, NO2 and d-limonene sources, and indoor photolysis rates; and they decreased with O3 deposition and nitric oxide (NO) sources. Photolysis was a strong OH formation mechanism for high NO, NO2, and HONO settings, but SCI/NO2 reactions weakly generated NO3 except for only a few cases. PMID:26855604

  3. Volatile organic compound conversion by ozone, hydroxyl radicals, and nitrate radicals in residential indoor air: Magnitudes and impacts of oxidant sources

    NASA Astrophysics Data System (ADS)

    Waring, Michael S.; Wells, J. Raymond

    2015-04-01

    Indoor chemistry may be initiated by reactions of ozone (O3), the hydroxyl radical (OH), or the nitrate radical (NO3) with volatile organic compounds (VOC). The principal indoor source of O3 is air exchange, while OH and NO3 formation are considered as primarily from O3 reactions with alkenes and nitrogen dioxide (NO2), respectively. Herein, we used time-averaged models for residences to predict O3, OH, and NO3 concentrations and their impacts on conversion of typical residential VOC profiles, within a Monte Carlo framework that varied inputs probabilistically. We accounted for established oxidant sources, as well as explored the importance of two newly realized indoor sources: (i) the photolysis of nitrous acid (HONO) indoors to generate OH and (ii) the reaction of stabilized Criegee intermediates (SCI) with NO2 to generate NO3. We found total VOC conversion to be dominated by reactions both with O3, which almost solely reacted with D-limonene, and also with OH, which reacted with D-limonene, other terpenes, alcohols, aldehydes, and aromatics. VOC oxidation rates increased with air exchange, outdoor O3, NO2 and D-limonene sources, and indoor photolysis rates; and they decreased with O3 deposition and nitric oxide (NO) sources. Photolysis was a strong OH formation mechanism for high NO, NO2, and HONO settings, but SCI/NO2 reactions weakly generated NO3 except for only a few cases.

  4. Role of hydroxyl radicals and mechanism of Escherichia coli inactivation on Ag/AgBr/TiO2 nanotube array electrode under visible light irradiation.

    PubMed

    Hou, Yang; Li, Xinyong; Zhao, Qidong; Chen, Guohua; Raston, Colin L

    2012-04-03

    A ternary Ag/AgBr/TiO(2) nanotube array electrode with enhanced visible-light activity was synthesized by a two-step approach including electrochemical process of anodization and an in situ photoassisted deposition strategy. The dramatically enhanced photoelectrocatalytic activity of the composite electrode was evaluated via the inactivation of Escherichia coli under visible light irradiation (λ>420 nm), whose performance of complete sterilization was much superior to other reference photocatalysts. PL, ESR, and radicals trapping studies revealed hydroxyl radicals were involved as the main active oxygen species in the photoelectrocatalytic reaction. The process of the damage of the cell wall and the cell membrane was directly observed by ESEM, TEM, and FTIR, as well as further confirmed by determination of potassium ion leakage from the killed bacteria. The present results pointed to oxidative attack from the exterior to the interior of the Escherichia coli by OH(•), O(2)(•-), holes and Br(0), causing the cell to die as the primary mechanism of photoelectrocatalytic inactivation.

  5. DNA sequence context as a determinant of the quantity and chemistry of guanine oxidation produced by hydroxyl radicals and one-electron oxidants.

    PubMed

    Margolin, Yelena; Shafirovich, Vladimir; Geacintov, Nicholas E; DeMott, Michael S; Dedon, Peter C

    2008-12-19

    DNA sequence context has emerged as a critical determinant of the location and quantity of nucleobase damage caused by many oxidizing agents. However, the complexity of nucleobase and 2-deoxyribose damage caused by strong oxidants such as ionizing radiation and the Fenton chemistry of Fe2+-EDTA/H2O2 poses a challenge to defining the location of nucleobase damage and the effects of sequence context on damage chemistry in DNA. To address this problem, we developed a gel-based method that allows quantification of nucleobase damage in oxidized DNA by exploiting Escherichia coli exonuclease III to remove fragments containing direct strand breaks and abasic sites. The rigor of the method was verified in studies of guanine oxidation by photooxidized riboflavin and nitrosoperoxycarbonate, for which different effects of sequence context have been demonstrated by other approaches (Margolin, Y., Cloutier, J. F., Shafirovich, V., Geacintov, N. E., and Dedon, P. C. (2006) Nat. Chem. Biol. 2, 365-366). Using duplex oligodeoxynucleotides containing all possible three-nucleotide sequence contexts for guanine, the method was used to assess the role of DNA sequence context in hydroxyl radical-induced guanine oxidation associated with gamma-radiation and Fe2+-EDTA/H2O2. The results revealed both differences and similarities for G oxidation by hydroxyl radicals and by one-electron oxidation by riboflavin-mediated photooxidation, which is consistent with the predominance of oxidation pathways for hydroxyl radicals other than one-electron oxidation to form guanine radical cations. Although the relative quantities of G oxidation produced by hydroxyl radicals were more weakly correlated with sequence-specific ionization potential than G oxidation produced by riboflavin, damage produced by both hydroxyl radical generators and riboflavin within two- and three-base runs of G showed biases in location that are consistent with a role for electron transfer in defining the location of the damage

  6. Salivary thiocyanate/nitrite inhibits hydroxylation of 2-hydroxybenzoic acid induced by hydrogen peroxide/Fe(II) systems under acidic conditions: possibility of thiocyanate/nitrite-dependent scavenging of hydroxyl radical in the stomach.

    PubMed

    Takahama, Umeo; Oniki, Takayuki

    2004-11-18

    Formation of OH radicals in the stomach is possible by Fenton-type reactions, as gastric juice contains ascorbic acid (AA), iron ions and H2O2. An objective of the present study is to elucidate the effects of salivary SCN- and NO2- on the hydroxylation of salicylic acid which was induced by H2O2/Fe(II) and AA/H2O2/Fe(II) systems. Thiocyanate ion inhibited the hydroxylation of salicylic acid by the above systems in acidic buffer solutions and in acidified saliva. The inhibition by SCN- was deduced to be due to SCN- -dependent scavenging of OH radicals. Nitrite ion could enhance the SCN- -dependent inhibition of the hydroxylation induced by AA/H2O2/Fe(II) systems. The enhancement was suggested to be due to scavenging of OH radicals by NO which was formed by the reactions among AA, HNO2 and SCN- contained in the reaction mixture. The concentrations of SCN- and NO2-, which were effective for the inhibition, were in ranges of their normal salivary concentrations. These results suggest that salivary SCN- can cooperate with NO2- to protect stomach from OH radicals formed by AA/H2O2/Fe(II) systems under acidic conditions.

  7. Gas-phase reaction of methyl isothiocyanate and methyl isocyanate with hydroxyl radicals under static relative rate conditions.

    PubMed

    Lu, Zhou; Hebert, Vincent R; Miller, Glenn C

    2014-02-26

    Gaseous methyl isothiocyanate (MITC), the principal breakdown product of the soil fumigant metam sodium (sodium N-methyldithiocarbamate), is an inhalation exposure concern to persons living near treated areas. Inhalation exposure also involves gaseous methyl isocyanate (MIC), a highly reactive and toxic transformation product of MITC. In this work, gas-phase hydroxyl (OH) radical reaction rate constants of MITC and MIC have been determined using a static relative rate technique under controlled laboratory conditions. The rate constants obtained are 15.36 × 10(-12) cm(3) molecule(-1) s(-1) for MITC and 3.62 × 10(-12) cm(3) molecule(-1) s(-1) for MIC. The average half-lives of MITC and MIC in the atmosphere are estimated to be 15.7 and 66.5 h, respectively. The molar conversion of MITC to MIC for OH radical reactions is 67% ± 8%, which indicates that MIC is the primary product of the MITC-OH reaction in the gas phase.

  8. Aircraft-borne, laser-induced fluorescence instrument for the in situ detection of hydroxyl and hydroperoxyl radicals

    NASA Technical Reports Server (NTRS)

    Wennberg, P. O.; Cohen, R. C.; Hazen, N. L.; Lapson, L. B.; Allen, N. T.; Hanisco, T. F.; Oliver, J. F.; Lanham, N. W.; Demusz, J. N.; Anderson, J. G.

    1994-01-01

    The odd-hydrogen radicals OH and HO2 are central to most of the gas-phase chemical transformations that occur in the atmosphere. Of particular interest is the role that these species play in controlling the concentration of stratospheric ozone. This paper describes an instrument that measures both of these species at volume mixing ratios below one part in 10(exp 14) in the upper troposphere and lower stratosphere. The hydroxyl radical (OH) is measured by laser induced fluorescence at 309 nm. Tunable UV light is used to pump OH to the first electric state near 282 nm. the laser light is produced by a high-repetition rate pulsed dye-laser powered with all solid-state pump lasers. HO2 is measured as OH after gas-phase titration with nitric oxide. Measurements aboard a NASA ER-2 aircraft demonstrate the capability of this instrument to perform reliably with very high signal-to-noise ratios (greater than 30) achieved in short integration times (less than 20 sec).

  9. Metal-independent production of hydroxyl radicals by halogenated quinones and hydrogen peroxide: an ESR spin trapping study.

    PubMed

    Zhu, Ben-Zhan; Zhao, Hong-Tao; Kalyanaraman, Balaraman; Frei, Balz

    2002-03-01

    The metal-independent production of hydroxyl radicals (*OH) from H(2)O(2) and tetrachloro-1,4-benzoquinone (TCBQ), a carcinogenic metabolite of the widely used wood-preservative pentachlorophenol, was studied by electron spin resonance methods. When incubated with the spin trapping agent 5,5-dimethyl-1-pyrroline N-oxide (DMPO), TCBQ and H(2)O(2) produced the DMPO/*OH adduct. The formation of DMPO/*OH was markedly inhibited by the *OH scavenging agents dimethyl sulfoxide (DMSO), ethanol, formate, and azide, with the concomitant formation of the characteristic DMPO spin trapping adducts with *CH(3), *CH(CH(3))OH, *COO(-), and *N(3), respectively. The formation of DMPO/*OH and DMPO/*CH(3) from TCBQ and H(2)O(2) in the absence and presence, respectively, of DMSO was inhibited by the trihydroxamate compound desferrioxamine, accompanied by the formation of the desferrioxamine-nitroxide radical. In contrast, DMPO/*OH and DMPO/*CH(3) formation from TCBQ and H(2)O(2) was not affected by the nonhydroxamate iron chelators bathophenanthroline disulfonate, ferrozine, and ferene, as well as the copper-specific chelator bathocuproine disulfonate. A comparative study with ferrous iron and H(2)O(2), the classic Fenton system, strongly supports our conclusion that *OH is produced by TCBQ and H(2)O(2) through a metal-independent mechanism. Metal-independent production of *OH from H(2)O(2) was also observed with several other halogenated quinones.

  10. Nitrones are able to release nitric oxide in aqueous environment under hydroxyl free radical attack.

    PubMed

    Croitoru, Mircea Dumitru; Ibolya, Fülöp; Pop, Maria Cristiana; Dergez, Timea; Mitroi, Brânduşa; Dogaru, Maria Titica; Tokés, Béla

    2011-10-30

    Importance of a nitric oxide donor that can act as a spin trap might bring some new therapeutic possibilities regarding the treatment of ischemic diseases by reducing the intensity of free radical produced reperfusion lesions. These substances might be also used as a new type of photo protectors since they can absorb UV radiation, capture free radicals formed by interaction of UV radiation with tissue constituents, and tanning of the skin will be permitted due to nitric oxide release. The purpose of this work was to measure the ability of nitrones to release nitric oxide and how different factors (temperature, nitrone concentration, and free radicals) influence the releasing ability. Mostly, indirect determination of nitric oxide was carried out, by measuring nitrite and nitrate amounts (as decomposition products of nitric oxide), all nitrones proved to release significant amounts of nitric oxide. Nitrite measurements were made based on an HPLC-VIS method that uses pre-column derivatization of nitrite by forming an azo dye (limit of quantification: 5ng/ml). No good correlation was found between the amount of nitric oxide and temperature for most studied nitrones but between the formation of nitric oxide and nitrone concentration an asymptotic correlation was found. Fenton reagent also yielded formation of nitric oxide from nitrones and formed amounts were not different from those recorded for UV irradiation. Most of the nitrones effectively released about 0.5% of the maximum amount of nitric oxide that is chemically possible and estimated concentrations of 0.1μM were present in the solutions during decomposition.

  11. Finding and characterizing the complexes of drug like molecules with quadruplex DNA: combined use of an enhanced hydroxyl radical cleavage protocol and NMR.

    PubMed

    Ranpura, Harikrushan; Bialonska, Dobroslawa; Bolton, Philip H

    2014-01-01

    Structural information on the complexes of drug like molecules with quadruplex DNAs can aid the development of therapeutics and research tools that selectively target specific quadruplex DNAs. Screening can identify candidate molecules that require additional evaluation. An enhanced hydroxyl radical cleavage protocol is demonstrated that can efficiently provide structural information on the complexes of the candidate molecules with quadruplex DNA. NMR methods have been used to offer additional structural information about the complexes as well as validate the results of the hydroxyl radical approach. This multi-step protocol has been demonstrated on complexes of the chair type quadruplex formed by the thrombin binding aptamer, d(GGTTGGTGTGGTTGG). The hydroxyl radical results indicate that NSC 176319, Cain's quinolinium that was found by screening, exhibits selective binding to the two TT loops. The NMR results are consistent with selective disruption of the hydrogen bonding between T4 and T13 as well as unstacking of these residues from the bottom quartet. Thus, the combination of screening, hydroxyl radical footprinting and NMR can find new molecules that selectively bind to quadruplex DNAs as well as provide structural information about their complexes.

  12. [Formation of hydrogen peroxide and hydroxyl radicals in aqueous solutions of L-amino acids by the action of X-rays and heat].

    PubMed

    Shtarkman, I N; Gudkov, S V; Chernikov, A V; Bruskov, V I

    2008-01-01

    The action of 1 mM solutions of L-amino acids in 5 mM phosphate buffer, pH 7.4, on the production of hydrogen peroxide and hydroxyl radicals under the action of X-rays and heating has been studied. Hydrogen peroxide was estimated by the method of enhanced luminescence in a system luminol-paraiodophenol-peroxidase and hydroxyl radicals were determined by using the fluorescence probe coumarin-3-carboxylic acid. It was shown that amino acids can be divided by their influence on H202 formation into three groups: those that reduce the yield of H202, that do not influence it, and that increase it. A similar action of amino acids was observed upon heating, but the composition of the groups was different. All amino acids lowered the formation of hydroxyl radicals under the action of X-rays, and the most effective among them were Cys > His > Phe = Met = Trp > Tyr. Met, His and Phe lowered the amount of hydroxyl radicals by heating, Ser raised it, whereas Tyr and Pro did not change it. Thus, amino acids differently influence the formation of reactive oxygen species by the action of X-rays and heat, and some of amino acids reveal themselves as effective natural antioxidants.

  13. CHEMISTRY OF FOG WATERS IN CALIFORNIA'S CENTRAL VALLEY: 1. IN SITU PHOTOFORMATION OF HYDROXYL RADICAL AND SINGLET MOLECULAR OXYGEN. (R825433)

    EPA Science Inventory

    The aqueous-phase photoformation of hydroxyl radical (characterOH) and singlet molecular oxygen (O2(1Δg) or 1O*

  14. Defining the enzyme binding domain of a ribonuclease III processing signal. Ethylation interference and hydroxyl radical footprinting using catalytically inactive RNase III mutants.

    PubMed Central

    Li, H; Nicholson, A W

    1996-01-01

    Ethylation interference and hydroxyl radical footprinting were used to identify substrate ribose-phosphate backbone sites that interact with the Escherichia coli RNA processing enzyme, ribonuclease III. Two RNase III mutants were employed, which bind substrate in vitro similarly as wild-type enzyme, but lack detectable phosphodiesterase activity. Specifically, altering glutamic acid at position 117 to lysine or alanine uncouples substrate binding from cleavage. The two substrates examined are based on the bacteriophage T7 R1.1 RNase III processing signal. One substrate, R1.1 RNA, undergoes accurate single cleavage at the canonical site, while a close variant, R1.1[WC-L] RNA, undergoes coordinate double cleavage. The interference and footprinting patterns for each substrate (i) overlap, (ii) exhibit symmetry and (iii) extend approximately one helical turn in each direction from the RNase III cleavage sites. Divalent metal ions (Mg2+, Ca2+) significantly enhance substrate binding, and confer stronger protection from hydroxyl radicals, but do not significantly affect the interference pattern. The footprinting and interference patterns indicate that (i) RNase III contacts the sugar-phosphate backbone; (ii) the RNase III-substrate interaction spans two turns of the A-form helix; and (iii) divalent metal ion does not play an essential role in binding specificity. These results rationalize the conserved two-turn helix motif seen in most RNase III processing signals, and which is necessary for optimal processing reactivity. In addition, the specific differences in the footprint and interference patterns of the two substrates suggest why RNase III catalyzes the coordinate double cleavage of R1.1[WC-L] RNA, and dsRNA in general, while catalyzing only single cleavage of R1.1 RNA and related substrates in which the scissle bond is within an asymmetric internal loop. Images PMID:8635475

  15. Method of making a membrane having hydrophilic and hydrophobic surfaces for adhering cells or antibodies by using atomic oxygen or hydroxyl radicals

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor); Spaulding, Glenn F. (Inventor)

    1994-01-01

    A portion of an organic polymer article such as a membrane is made hydrophilic by exposing a hydrophobic surface of the article to a depth of about 50 to about 5000 angstroms to atomic oxygen or hydroxyl radicals at a temperature below 100C., preferably below 40 C, to form a hydrophilic uniform surface layer of hydrophilic hydroxyl groups. The atomic oxygen and hydroxyl radicals are generated by a flowing afterglow microwave discharge, and the surface is outside of a plasma produced by the discharge. A membrane having both hydrophilic and hydrophobic surfaces can be used in an immunoassay by adhering antibodies to the hydrophobic surface. In another embodiment, the membrane is used in cell culturing where cells adhere to the hydrophilic surface. Prior to adhering cells, the hydrophilic surface may be grafted with a compatibilizing compound. A plurality of hydrophilic regions bounded by adjacent hydrophobic regions can be produced such that a maximum of one cell per each hydrophilic region adheres.

  16. Exposure of beta H-crystallin to hydroxyl radicals enhances the transglutaminase-susceptibility of its existing amine-donor and amine-acceptor sites.

    PubMed Central

    Groenen, P J; Seccia, M; Smulders, R H; Gravela, E; Cheeseman, K H; Bloemendal, H; de Jong, W W

    1993-01-01

    beta H-crystallin was exposed to radiolytically generated hydroxyl radicals at defined radical concentrations, and its capacity to act as an amine-acceptor substrate and as an amine-donor substrate for transglutaminase were investigated. [14C]Methylamine was used as a probe for labelling amine-acceptor sites; a novel biotinylated hexapeptide was used to label amine-donor sites. The results demonstrate that both primary amine incorporation and hexapeptide incorporation by transglutaminase are considerably increased after oxidative attack on the crystallin. The identity of the labelled subunits was established, and it is shown that, in both cases, this increased incorporation is not due to the production of new substrates, but that the existing incorporation sites become more susceptible. Moreover, using the newly developed probe, we could identify, for the first time, the major crystallin subunits active as amine-donor substrates (both before and after treatment) to be beta B1-, beta A3- and beta A4-crystallin. These data support the proposal that oxidative stress and transglutaminase activity may be jointly involved in the changes found in lens crystallins with age and in the development of cataract. Images Figure 1 Figure 2 Figure 3 PMID:7902086

  17. Line emission of sodium and hydroxyl radicals in single-bubble sonoluminescence.

    PubMed

    Schneider, Julia; Pflieger, Rachel; Nikitenko, Sergey I; Shchukin, Dmitry; Möhwald, Helmuth

    2011-01-20

    Spectroscopic studies of single-bubble sonoluminescence (SBSL) in water and aqueous sodium chloride solutions with a defined concentration of argon were performed as a function of the driving acoustic pressure. The broad-band continuum ranging from 200 to 700 nm is characterized by fits using Planck's law of blackbody radiation. The obtained blackbody temperatures are in the range of 10(4) K and are revealed to be independent of the presence of a salt and the acoustic pressure, whereas the SL intensity increases by a factor of more than 10 within the studied acoustic pressure range. The different trends followed by SL intensity and blackbody temperatures question the blackbody model. In solutions with 70 mbar of argon, line emissions of OH(•) radicals and Na* are observed. The shape of the OH(•) radical emission spectrum is very similar to that in MBSL spectra, indicating the strong similarity of intrabubble conditions. An increase of the acoustic pressure causes the continuum to overlap the lines until they become indistinguishable. The emission line of Na* in NaCl is observed only at high NaCl concentrations. When sodium dodecylsulfate is used a pronounced Na* line is already observed in a 1 mM solution thanks to enrichment of sodium ions at the interface. The results presented in this work reveal the strong similarity of SBSL and MBSL under certain experimental conditions.

  18. Oxidation of methanol by hydroxyl radicals in aqueous solution under simulated cloud droplet conditions

    NASA Astrophysics Data System (ADS)

    Monod, Anne; Chebbi, Abderaouf; Durand-Jolibois, Régine; Carlier, Patrick

    The results of a detailed mechanistic study of aqueous-phase OH-oxidation of methanol are presented. Analysis of reaction products by specific chromatographic methods revealed that hydrated formaldehyde is not the only stable primary reaction product. Formic acid and/or formate ion are also stable primary molecular reaction products of methanol OH-oxidation. The branching ratios for their formation are highly pH dependent. At pH=7, hydrated formaldehyde is the dominant molecular reaction product (ratio 4.5 : 1 for hydrated formaldehyde : formate ion), whereas at pH=2, formic acid is the dominant product (ratio 3.7 : 1 for formic acid : hydrated formaldehyde). At all pH studied, the sum of the primary stable products represents 49 (±11)% of methanol removal, in agreement with the amount of OOCH 2OH radicals formed relative to methanol removal 48(±2)%. The formation of primary formic acid at pH=2 is attributed to OOCH 2OH self-reaction, and the strong pH effect is attributed to the base-catalyzed decomposition of OOCH 2OH leading to the formation of hydrated formaldehyde. Evaporation and/or an addition reaction between CH 2OH and HO 2 radicals leading to the formation of hydroxymethyl hydroperoxide is proposed to explain the missing yields. The implications of this mechanism to atmospheric chemistry are discussed.

  19. Gas-Phase Reaction of Hydroxyl Radical with p-Cymene over an Extended Temperature Range.

    PubMed

    Bedjanian, Yuri; Morin, Julien; Romanias, Manolis N

    2015-11-12

    The kinetics of the reaction of OH radicals with p-cymene has been studied in the temperature range of 243-898 K using a flow reactor combined with a quadrupole mass spectrometer: OH + p-cymene → products. The reaction rate constant was determined as a result of absolute measurements, from OH decay kinetics in excess of p-cymene and employing the relative rate method with OH reactions with n-pentane, n-heptane,1,3-dioxane, HBr, and Br2 as the reference ones. For the rate coefficient of the H atom abstraction channel, the expression k1b = (3.70 ± 0.42) × 10(-11) exp[-(772 ± 72)/T] was obtained over the temperature range of 381-898 K. The total rate constant (addition + abstraction) determined at T = 243-320 K was k1 = (1.82 ± 0.48) × 10(-12) exp[(607 ± 70)/T] or, in a biexponential form, k1 = k1a + k1b = 3.7 × 10(-11) exp(-772/T) + 6.3 × 10(-13) exp(856/T), independent of the pressure between 1 and 5 Torr of helium. In addition, our results indicate that the reaction pathway involving alkyl radical elimination upon initial addition of OH to p-cymene is most probably unimportant.

  20. Interaction of the Pseudomonas aeruginosa secretory products pyocyanin and pyochelin generates hydroxyl radical and causes synergistic damage to endothelial cells. Implications for Pseudomonas-associated tissue injury.

    PubMed Central

    Britigan, B E; Roeder, T L; Rasmussen, G T; Shasby, D M; McCormick, M L; Cox, C D

    1992-01-01

    Pyocyanin, a secretory product of Pseudomonas aeruginosa, has the capacity to undergo redox cycling under aerobic conditions with resulting generation of superoxide and hydrogen peroxide. By using spin trapping techniques in conjunction with electron paramagnetic resonance spectrometry (EPR), superoxide was detected during the aerobic reduction of pyocyanin by NADH or porcine endothelial cells. No evidence of hydroxyl radical formation was detected. Chromium oxalate eliminated the EPR spectrum of the superoxide-derived spin adduct resulting from endothelial cell exposure to pyocyanin, suggesting superoxide formation close to the endothelial cell plasma membrane. We have previously reported that iron bound to the P. aeruginosa siderophore pyochelin (ferripyochelin) catalyzes the formation of hydroxyl free radical from superoxide and hydrogen peroxide via the Haber-Weiss reaction. In the present study, spin trap evidence of hydroxyl radical formation was detected when NADH and pyocyanin were allowed to react in the presence of ferripyochelin. Similarly, endothelial cell exposure to pyocyanin and ferripyochelin also resulted in hydroxyl radical production which appeared to occur in close proximity to the cell surface. As assessed by 51Cr release, endothelial cells which were treated with pyocyanin or ferripyochelin alone demonstrated minimal injury. However, endothelial cell exposure to the combination of pyochelin and pyocyanin resulted in 55% specific 51Cr release. Injury was not observed with the substitution of iron-free pyochelin and was diminished by the presence of catalase or dimethyl thiourea. These data suggest the possibility that the P. aeruginosa secretory products pyocyanin and pyochelin may act synergistically via the generation of hydroxyl radical to damage local tissues at sites of pseudomonas infection. PMID:1469082

  1. Oxidative transformation of micropollutants during municipal wastewater treatment: comparison of kinetic aspects of selective (chlorine, chlorine dioxide, ferrate VI, and ozone) and non-selective oxidants (hydroxyl radical).

    PubMed

    Lee, Yunho; von Gunten, Urs

    2010-01-01

    Chemical oxidation processes have been widely applied to water treatment and may serve as a tool to minimize the release of micropollutants (e.g. pharmaceuticals and endocrine disruptors) from municipal wastewater effluents into the aquatic environment. The potential of several oxidants for the transformation of selected micropollutants such as atenolol, carbamazepine, 17 alpha-ethinylestradiol (EE2), ibuprofen, and sulfamethoxazole was assessed and compared. The oxidants include chlorine, chlorine dioxide, ferrate(VI), and ozone as selective oxidants versus hydroxyl radicals as non-selective oxidant. Second-order rate constants (k) for the reaction of each oxidant show that the selective oxidants react only with some electron-rich organic moieties (ERMs), such as phenols, anilines, olefins, and deprotonated-amines. In contrast, hydroxyl radicals show a nearly diffusion-controlled reactivity with almost all organic moieties (k>or=10(9)M(-1) s(-1)). Due to a competition for oxidants between a target micropollutant and wastewater matrix (i.e. effluent organic matter, EfOM), a higher reaction rate with a target micropollutant does not necessarily translate into more efficient transformation. For example, transformation efficiencies of EE2, a phenolic micropollutant, in a selected wastewater effluent at pH 8 varied only within a factor of 7 among the selective oxidants, even though the corresponding k for the reaction of each selective oxidant with EE2 varied over four orders of magnitude. In addition, for the selective oxidants, the competition disappears rapidly after the ERMs present in EfOM are consumed. In contrast, for hydroxyl radicals, the competition remains practically the same during the entire oxidation. Therefore, for a given oxidant dose, the selective oxidants were more efficient than hydroxyl radicals for transforming ERMs-containing micropollutants, while hydroxyl radicals are capable of transforming micropollutants even without ERMs. Besides Ef

  2. Effect of adenosine A(2A) receptor antagonists and L-DOPA on hydroxyl radical, glutamate and dopamine in the striatum of 6-OHDA-treated rats.

    PubMed

    Gołembiowska, Krystyna; Dziubina, Anna

    2012-02-01

    A(2A) adenosine receptor antagonists have been proposed as a new therapy of PD. Since oxidative stress plays an important role in the pathogenesis of PD, we studied the effect of the selective A(2A) adenosine receptor antagonists 8-(-3-chlorostyryl)caffeine (CSC) and 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) on hydroxyl radical generation, and glutamate (GLU) and dopamine (DA) extracellular level using a microdialysis in the striatum of 6-OHDA-treated rats. CSC (1 mg/kg) and ZM 241385 (3 mg/kg) given repeatedly for 14 days decreased the production of hydroxyl radical and extracellular GLU level, both enhanced by prior 6-OHDA treatment in dialysates from the rat striatum. CSC and ZM 241385 did not affect DA and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) extracellular levels in the striatum of 6-OHDA-treated rats. L-DOPA (6 mg/kg) given twice daily for two weeks in the presence of benserazide (3 mg/kg) decreased striatal hydroxyl radical and glutamate extracellular level in 6-OHDA-treated rats. At the same time, L-DOPA slightly but significantly increased the extracellular levels of DOPAC and HVA. A combined repeated administration of L-DOPA and CSC or ZM 241385 did not change the effect of L-DOPA on hydroxyl radical production and glutamate extracellular level in spite of an enhancement of extracellular DA level by CSC and elevation of extracellular level of DOPAC and HVA by ZM 241385. The data suggest that the 6-OHDA-induced damage of nigrostriatal DA-terminals is related to oxidative stress and excessive release of glutamate. Administration of L-DOPA in combination with CSC or ZM 241385, by restoring striatal DA-glutamate balance, suppressed 6-OHDA-induced overproduction of hydroxyl radical.

  3. Quasiclassical trajectory study of the vibrational quenching of hydroxyl radicals through collision with O atoms.

    PubMed

    Viswanathan, Raji; Dolgos, Michelle; Hinde, Robert J

    2007-02-08

    The collisional removal of vibrationally excited OH radicals by O atoms is studied by the quasiclassical trajectory method. To evaluate the effect of different topological features on the scattering processes two different global potential energy surfaces, DMBE IV and TU, are used. Results for reactive, exchange, and inelastic scattering probabilities are reported for central collisions (with zero total angular momentum) with a fixed relative translational energy for vibrational levels of OH ranging from nu=1 to v=8. Vibrational state distributions of product molecules are also compared on the two potential energy surfaces. Both surfaces predict higher probabilities for reaction than for exchange or inelastic scattering. The vibrational state distributions of the product diatomic molecules are different on the two surfaces. In particular, the two surfaces give substantially different probabilities for multiquantum OH vibrational relaxation transitions OH(v)+O-->OH(v')+O.

  4. Formation of hydroxyl radicals from photolysis of secondary organic aerosol material

    NASA Astrophysics Data System (ADS)

    Badali, K. M.; Zhou, S.; Aljawhary, D.; Antiñolo, M.; Chen, W. J.; Lok, A.; Mungall, E.; Wong, J. P. S.; Zhao, R.; Abbatt, J. P. D.

    2015-02-01

    This paper demonstrates that OH radicals are formed by photolysis of secondary organic aerosol (SOA) material formed by terpene ozonolysis. The SOA aerosol is collected on filters, dissolved in water containing a radical trap (benzoic acid), and then exposed to ultraviolet light in a photochemical reactor. The OH formation rates, which are similar for both α-pinene and limonene SOA, are measured from the formation rate of p-hydroxybenzoic acid as measured using offline HPLC analysis. To evaluate whether the OH is formed by photolysis of H2O2 or organic hydroperoxides (ROOH), the peroxide content of the SOA was measured using the horseradish peroxidase-dichlorofluorescein (HRP-DCF) assay, which was calibrated using H2O2. The OH formation rates from SOA are five times faster than from the photolysis of H2O2 solutions whose concentrations correspond to the peroxide content of the SOA solutions assuming that the HRP-DCF signal arises from H2O2 alone. The higher rates of OH formation from SOA are likely due to ROOH photolysis. This result is substantiated by photolysis experiments conducted with t-butyl hydroperoxide and cumene hydroperoxide which produce over three times more OH than photolysis of equivalent concentrations of H2O2. Relative to the peroxide level in the SOA, the quantum yield for OH generation from α-pinene SOA is 0.8 ± 0.4. This is the first demonstration of an efficient photolytic source of OH in SOA, one that may affect both cloudwater and aerosol chemistry.

  5. Formation of hydroxyl radicals from photolysis of secondary organic aerosol material

    NASA Astrophysics Data System (ADS)

    Badali, K. M.; Zhou, S.; Aljawhary, D.; Antiñolo, M.; Chen, W. J.; Lok, A.; Mungall, E.; Wong, J. P. S.; Zhao, R.; Abbatt, J. P. D.

    2015-07-01

    This paper demonstrates that OH radicals are formed by photolysis of secondary organic aerosol (SOA) material formed by terpene ozonolysis. The SOA is collected on filters, dissolved in water containing a radical trap (benzoic acid), and then exposed to ultraviolet light in a photochemical reactor. The OH formation rates, which are similar for both α-pinene and limonene SOA, are measured from the formation rate of p-hydroxybenzoic acid as measured using offline HPLC analysis. To evaluate whether the OH is formed by photolysis of H2O2 or organic hydroperoxides (ROOH), the peroxide content of the SOA was measured using the horseradish peroxidase-dichlorofluorescein (HRP-DCF) assay, which was calibrated using H2O2. The OH formation rates from SOA are 5 times faster than from the photolysis of H2O2 solutions whose concentrations correspond to the peroxide content of the SOA solutions, assuming that the HRP-DCF signal arises from H2O2 alone. The higher rates of OH formation from SOA are likely due to ROOH photolysis, but we cannot rule out a contribution from secondary processes as well. This result is substantiated by photolysis experiments conducted with t-butyl hydroperoxide and cumene hydroperoxide which produce over 3 times more OH than photolysis of equivalent concentrations of H2O2. Relative to the peroxide level in the SOA and assuming that the peroxides drive most of the ultraviolet absorption, the quantum yield for OH generation from α-pinene SOA is 0.8 ± 0.4. This is the first demonstration of an efficient photolytic source of OH in SOA, one that may affect both cloud water and aerosol chemistry.

  6. Thermochemistry of aqueous hydroxyl radical from advances in photoacoustic calorimetry and ab initio continuum solvation theory.

    PubMed

    Autrey, Tom; Brown, Aaron K; Camaioni, Donald M; Dupuis, Michel; Foster, Nancy S; Getty, April

    2004-03-31

    Photoacoustic signals from dilute ( approximately 30 mM) solutions of H2O2 were measured over the temperature range from 10 to 45 degrees C to obtain the reaction enthalpy and volume change for H2O2(aq) --> 2 OH(aq) from which we ultimately determined DeltafG degrees , DeltafH degrees and partial molal volume, v degrees , of OH (aq). We find DeltarH = 46.8 +/- 1.4 kcal/mol, which is 4 kcal/mol smaller than the gas-phase bond energy, and DeltaVr = 6.5 +/- 0.4 mL/mol. The v degrees for OH in water is 14.4 +/- 0.4 mL/ml: smaller than the v degrees of water. Using ab intio continuum theory, the hydration free energy is calculated to be -3.9 +/- 0.3 kcal/mol (for standard states in number density concentration units) by a novel approach devised to capture in the definition of the solute cavity the strength and specific interactions of the solute with a water solvent molecule. The shape of the cavity is defined by "rolling" a three-dimensional electron density isocontour of water on the ab initio water-OH minimum interaction surface. The value of the contour is selected to reproduce the volume of OH in water. We obtain for OH(aq): DeltafH degrees = -0.2 +/- 1.4 and DeltafG degrees = 5.8 +/- 0.4 kcal/mol that are in agreement with literature values. The results provide confidence in the pulsed PAC technique for measuring aqueous thermochemistry of radicals and open the way to obtaining thermochemistry for most radicals that can be formed by reaction of OH with aqueous substrates while advancing the field of continuum solvation theory toward ab initio-defined solute cavities.

  7. Reduction of DNA fragmentation and hydroxyl radical production by hyaluronic acid and chondroitin-4-sulphate in iron plus ascorbate-induced oxidative stress in fibroblast cultures.

    PubMed

    Campo, Giuseppe M; Avenoso, Angela; Campo, Salvatore; D'Ascola, Angela; Ferlazzo, Alida M; Calatroni, Alberto

    2004-06-01

    Glycosaminoglycans (GAGs), components of extracellular matrix, are thought to play important roles in cell proliferation and differentiation in the repair process of injured tissue. Oxidative stress is one of the most frequent causes of tissue and cell injury and the consequent lipid peroxidation is the main manifestation of free radical damage. It has been found to play an important role in the evolution of cell death. Since several reports have shown that hyaluronic acid (HYA) and chondroitin-4-sulphate (C4S) are able to inhibit lipid peroxidation during oxidative stress, We investigated the antioxidant capacity of these GAGs in reducing oxidative damage in fibroblast cultures. Free radicals production was induced by the oxidizing system employing iron (Fe2+) plus ascorbate. We evaluated cell death, membrane lipid peroxidation, DNA damage, protein oxidation, hydroxyl radical (OH*) generation and endogenous antioxidant depletion in human skin fibroblast cultures. The exposition of fibroblasts to FeSO4 and ascorbate caused inhibition of cell growth and cell death, increased OH* production determined by the aromatic trap method; furthermore it caused DNA strand breaks and protein oxidation as shown by the DNA fragments analysis and protein carbonyl content, respectively. Moreover, it enhanced lipid peroxidation evaluated by the analysis of conjugated dienes (CD) and decreased antioxidant defenses assayed by means of measurement of superoxide dismutase (SOD) and catalase (CAT) activities. When fibroblasts were treated with two different doses of HYA or C4S a protective effect, following oxidative stress induction, was shown. In fact these GAGs were able to limit cell death, reduced DNA fragmentation and protein oxidation, decreased OH* generation, inhibited lipid peroxidation and improved antioxidant defenses. Our results confirm the antioxidant activity of HYA and C4S and this could represent a useful step in the understanding of the exact role played by GAGs in

  8. A better understanding of hydroxyl radical photochemical sources in cloud waters collected at the puy de Dôme station - experimental versus modelled formation rates

    NASA Astrophysics Data System (ADS)

    Bianco, A.; Passananti, M.; Perroux, H.; Voyard, G.; Mouchel-Vallon, C.; Chaumerliac, N.; Mailhot, G.; Deguillaume, L.; Brigante, M.

    2015-08-01

    The oxidative capacity of the cloud aqueous phase is investigated during three field campaigns from 2013 to 2014 at the top of the puy de Dôme station (PUY) in France. A total of 41 cloud samples are collected and the corresponding air masses are classified as highly marine, marine and continental. Hydroxyl radical (HO•) formation rates (RHO•f) are determined using a photochemical setup (xenon lamp that can reproduce the solar spectrum) and a chemical probe coupled with spectroscopic analysis that can trap all of the generated radicals for each sample. Using this method, the obtained values correspond to the total formation of HO• without its chemical sinks. These formation rates are correlated with the concentrations of the naturally occurring sources of HO•, including hydrogen peroxide, nitrite, nitrate and iron. The total hydroxyl radical formation rates are measured as ranging from approximately 2 × 10-11 to 4 × 10-10 M s-1, and the hydroxyl radical quantum yield formation (ΦHO•) is estimated between 10-4 and 10-2. Experimental values are compared with modelled formation rates calculated by the model of multiphase cloud chemistry (M2C2), considering only the chemical sources of the hydroxyl radicals. The comparison between the experimental and the modelled results suggests that the photoreactivity of the iron species as a source of HO• is overestimated by the model, and H2O2 photolysis represents the most important source of this radical (between 70 and 99 %) for the cloud water sampled at the PUY station (primarily marine and continental).

  9. Thermochemistry of Aqueous Hydroxyl Radical from Advances in Photoacoustic Calorimetry and ab Initio Continum Solvation Theory

    SciTech Connect

    Autrey, Thomas; Brown, Aaron K.; Camaioni, Donald M.; Dupuis, Michel; Foster, Nancy S.; Getty, April D.

    2004-03-31

    Photoacoustic signals from dilute ({approx}30 mM) solutions of H{sub 2}O{sub 2} were measured over the temperature range from 10-45 C to obtain the reaction enthalpy and volume change for H{sub 2}O{sub 2}(aq) {yields} 2 OH(aq) from which we ultimately determined {Delta}{sub f}G{sup o}, {Delta}{sub f}H{sup o} and partial molal volume, v{sup o}, of OH (aq). We find {Delta}{sub r}H = 46.8 {+-} 1.4 kcal/mol, which is 4 kcal/mol smaller than the gas phase bond energy, and {Delta}V{sub r} = 6.5 {+-} 0.4 mL/mol. The v{sup o} for OH in water is 14.4 {+-} 0.4 mL/ml: smaller than the v{sup o} of water. Using ab initio continuum theory, the hydration free energy is calculated to be -3.9 {+-} 0.3 kcal/mol (for standard states in number density concentration units) by a novel approach devised to capture in the definition of the solute cavity the strength and specific interactions of the solute with a water solvent molecule. The shape of the cavity is defined by ''rolling'' a 3 dimensional electron density isocontour of water on the ab initio water-OH minimum interaction surface. The value of the contour is selected to reproduce the volume of OH in water. We obtain for OH(aq): {Delta}{sub f}H{sup o} = -0.2 {+-} 1.4 and {Delta}{sub f}G{sup o} = 5.8 {+-} 0.4 kcal/mol that are in agreement with literature values. The results provide confidence in the pulsed PAC technique for measuring aqueous thermochemistry of radicals and open the way to obtaining thermochemistry for most radicals that can be formed by reaction of OH with aqueous substrates while advancing the field of continuum solvation theory towards ab initio-defined solute cavities.

  10. The conical intersection dominates the generation of tropospheric hydroxyl radicals from NO2 and H2O.

    PubMed

    Fang, Qiu; Han, Juan; Jiang, Jieling; Chen, Xuebo; Fang, Weihai

    2010-04-08

    In the present work, we report a quantitative understanding on how to generate hydroxyl radicals from NO(2) and H(2)O in the troposphere upon photoexcitation at 410 nm by using multiconfigurational perturbation theory and density functional theory. The conical intersections dominate the nonadiabatic relaxation processes after NO(2) irradiated at approximately 410 nm in the troposphere and further control the generation of OH radical by means of hydrogen abstraction. In agreement with two-component fluorescence observed by laser techniques, there are two different photophysical relaxation channels along decreasing and increasing O-N-O angle of NO(2). In the former case, the conical intersection between B(2)B(1) and A(2)B(2) (CI ((2)B(2)/(2)B(1)) first funnels NO(2) out of the Franck-Condon region of B(2)B(1) and relaxes to the A(2)B(2) surface. Following the primary relaxation, the conical intersection between A(2)B(2) and X(2)A(1) (CI((2)B(2)/(2)A(1))) drives NO(2) to decay into highly vibrationally excited X(2)A(1) state that is more than 20,000 cm(-1) above zeroth-order |n(1),n(2),n(3) = 0 vibrational level. In the latter case, increasing the O-N-O angle leads NO(2) to relax to a minimum of B(2)B(1) with a linear O-N-O arrangement. This minimum point is also funnel region between B(2)B(1) and X(2)A(1) (CI((2)B(1)/(2)A(1))) and leads NO(2) to relax into a highly vibrationally excited X(2)A(1) state. The high energetic level of vibrationally excited state has enough energy to overcome the barrier of hydrogen abstraction (40-50 kcal/mol) from water vapor, producing OH ((2)Pi(3/2)) radicals. The collision between NO(2) and H(2)O molecules not only is a precondition of hydrogen abstraction but induces the faster internal conversion (CIIC) via conical intersections. The faster internal conversion favors more energy transfer from electronically excited states into highly vibrationally excited X(2)A(1) states. The collision (i.e., the heat motion of molecules) functions

  11. Saturated fluorescence measurements of the hydroxyl radical in laminar high-pressure flames

    NASA Technical Reports Server (NTRS)

    Carter, Campbell D.; King, Galen B.; Laurendeau, Normand M.

    1990-01-01

    The efficacy of laser saturated fluorescence (LSF) for OH concentration measurements in high pressure flames was studied theoretically and experimentally. Using a numerical model describing the interaction of hydroxyl with nonuniform laser excitation, the effect of pressure on the validity of the balanced cross-rate model was studied along with the sensitivity of the depopulation of the laser-coupled levels to the ratio of rate coefficients describing: (1) electronic quenching to (sup 2) Sigma (+) (v double prime greater than 0), and (2) vibrational relaxation from v double prime greater than 0 to v double prime = 0. At sufficiently high pressures and near-saturated conditions, the total population of the laser-coupled levels reaches an asymptotic value, which is insensitive to the degree of saturation. When the ratio of electronic quenching to vibrational relaxation is small and the rate of coefficients for rotational transfer in the ground and excited electronic states are nearly the same, the balanced cross-rate model remains a good approximation for all pressures. When the above ratio is large, depopulation of the laser-coupled levels becomes significant at high pressures, and thus the balanced cross-rate model no longer holds. Under these conditions, however, knowledge of the depletion of the laser-coupled levels can be used to correct the model. A combustion facility for operation up to 20 atm was developed to allow LSF measurements of OH in high pressure flames. Using this facility, partial saturation in laminar high pressure (less than or equal to 12.3 atm) C2H6/O2/N2 flames was achieved. To evaluate the limits of the balanced cross-rate model, absorption and calibrated LSF measurements at 3.1 and 6.1 atm were compared. The fluorescence voltages were calibrated with absorption measurements in an atmospheric flame and corrected for their finite sensitivity to quenching with: (1) estimated quenching rate coefficients, and (2) an in situ measurement from a

  12. Velocity distributions of hydrogen atoms and hydroxyl radicals produced through solar photodissociation of water

    NASA Technical Reports Server (NTRS)

    Wu, C. Y. R.; Chen, F. Z.

    1993-01-01

    The velocity distributions of H and OH fragments produced through solar photodissociation of gaseous H2O molecules under collisionless conditions are presented. The calculations are carried out using: the most recently available absolute partial cross sections for the production of H and OH through photodissociation of H2O from its absorption onset at 1860 A down to 500 A; the newly available vibrational and rotational energy distributions of both the excited and ground state OH photofragments; the calculated cross sections for the total dissociation processes; and the integrated solar flux in 10 A increments from 500 to 1860 A in the continuum regions and the specific wavelength and flux at the bright solar lines. The calculated results show that the H atoms and the OH radicals produced exhibit multiple velocity groups. Since most current cometary modeling uses a single velocity of 20 km/sec associated with the photodissociation of H2O, the present results may be useful in interpreting the many peaks observed in the velocity distributions of the H Lyman alpha and H alpha of comets.

  13. Dimers in α-pinene secondary organic aerosol: effect of hydroxyl radical, ozone, relative humidity and aerosol acidity

    NASA Astrophysics Data System (ADS)

    Kristensen, K.; Cui, T.; Zhang, H.; Gold, A.; Glasius, M.; Surratt, J. D.

    2014-04-01

    The formation of secondary organic aerosol (SOA) from both ozonolysis and hydroxyl radical (OH)-initiated oxidation of α-pinene under conditions of high nitric oxide (NO) concentrations with varying relative humidity (RH) and aerosol acidity was investigated in the University of North Carolina dual outdoor smog chamber facility. SOA formation from ozonolysis of α-pinene was enhanced relative to that from OH-initiated oxidation in the presence of initially high-NO conditions. However, no effect of RH on SOA mass was evident. Ozone (O3)-initiated oxidation of α-pinene in the presence of ammonium sulfate (AS) seed coated with organic aerosol from OH-initiated oxidation of α-pinene showed reduced nucleation compared to ozonolysis in the presence of pure AS seed aerosol. The chemical composition of α-pinene SOA was investigated by ultra-performance liquid chromatography/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS), with a focus on the formation of carboxylic acids and high-molecular weight dimers. A total of eight carboxylic acids and four dimers were identified, constituting between 8 and 12% of the total α-pinene SOA mass. OH-initiated oxidation of α-pinene in the presence of nitrogen oxides (NOx) resulted in the formation of highly oxidized carboxylic acids, such as 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA) and diaterpenylic acid acetate (DTAA). The formation of dimers was observed only in SOA produced from the ozonolysis of α-pinene in the absence of NOx, with increased concentrations by a factor of two at higher RH (50-90%) relative to lower RH (30-50%). The increased formation of dimers correlates with an observed increase in new particle formation at higher RH due to nucleation. Increased aerosol acidity was found to have a negligible effect on the formation of the dimers. SOA mass yield did not influence the chemical composition of SOA formed from α-pinene ozonolysis with respect to

  14. Theoretical studies of the reaction of hydroxyl radical with methyl acetate.

    PubMed

    Yang, Lei; Liu, Jing-yao; Li, Ze-sheng

    2008-07-17

    The mechanisms and the kinetics of the OH (OD) radicals with methyl acetate CH3C(O)OCH3 are investigated theoretically. The dual-level direct dynamics method is employed in the calculation of the rate constants. The optimized geometries and frequencies and the gradients of the stationary points are calculated at the MP2/6-311G(d,p) level. The energetic information of potential energy surfaces is further refined by the multicoefficient correlation method based on QCISD (MC-QCISD) using the MP2/6-311G(d,p) geometries. Four channels are found for the title reaction. The calculated results reveal that there exists an attractive well (reactant complex) in each entrance H-abstraction channel, that is, the H-abstraction reaction makes a stepwise mechanism. The rate constants are calculated by the canonical variational transition-state theory (CVT) with the interpolated single-point energies (ISPE) approach in the temperature range of 200-1200 K. The small-curvature tunneling effect (SCT) approximation is used to evaluate the transmission coefficient. The calculated rate constants are in good agreement with the experimental ones in the measured temperature range. It is shown that the "out-of-plane hydrogen abstraction" from the methoxy end is the dominant channel at the lower temperatures, and the other two H-abstraction channels should be taken into account with the temperatures increasing. The kinetic isotope effects (KIEs) for the three H-abstraction channels and the total reaction are "inverse", and these theoretically calculated KIEs as a function of temperature are expected to be useful for the future laboratory investigation.

  15. Unprecedented hydroxyl radical-dependent two-step chemiluminescence production by polyhalogenated quinoid carcinogens and H2O2.

    PubMed

    Zhu, Ben-Zhan; Mao, Li; Huang, Chun-Hua; Qin, Hao; Fan, Rui-Mei; Kalyanaraman, Balaraman; Zhu, Jun-Ge

    2012-10-02

    Most chemiluminescence (CL) reactions usually generate only one-step CL, which is rarely dependent on the highly reactive and biologically/environmentally important hydroxyl radicals ((•)OH). Here, we show that an unprecedented two-step CL can be produced by the carcinogenic tetrachloro-1,4-benzoquinone (also known as p-chloranil) and H(2)O(2), which was found to be well-correlated to and directly dependent on its two-step metal-independent production of (•)OH. We proposed that (•)OH-dependent formation of quinone-dioxetane and electronically excited carbonyl species might be responsible for this unusual two-step CL production by tetrachloro-1,4-benzoquinone/H(2)O(2). This is a unique report of a previously undefined two-step CL-producing system that is dependent on intrinsically formed (•)OH. These findings may have potential applications in detecting and quantifying (•)OH and the ubiquitous polyhalogenated aromatic carcinogens, which may have broad biological and environmental implications for future research on these types of important species.

  16. Oxidative and nitrosative stress induced in myofibrillar proteins by a hydroxyl-radical-generating system: impact of nitrite and ascorbate.

    PubMed

    Villaverde, Adriana; Parra, Vita; Estévez, Mario

    2014-03-12

    Understanding the chemistry behind the redox properties of nitrite and ascorbate is essential to identify the impact of curing agents on food quality and optimize the formulation of cured meat products. This study was designed to gain insight into the interactions between curing agents and myofibrillar proteins (MPs) during in vitro oxidation by a hydroxyl-radical-generating system. MPs (4 mg/mL) were oxidized for 4 days at 37 °C under constant stirring with 25 μM iron(III) and 2.5 mM hydrogen peroxide. Dependent upon the addition of nitrite (0, 75, and 150 mg/L) and ascorbate (0, 250, and 500 mg/L), nine different reaction units were prepared in triplicate (n = 3) according to a total factorial design. Upon completion of the oxidation assay, samples were analyzed for the concentration of tryptophan (TRP), α-aminoadipic semialdehyde (AAS), Schiff bases (SBs), and 3-nitrotyrosine (3NT). Ascorbate at 250 mg/L significantly inhibited the depletion of TRP (∼20% inhibition) and the formation of AAS and SBs (>90% inhibition) in MP suspensions. Nitrite, alone, had a negligible effect on protein oxidation but induced the formation of a specific marker of nitrosative stress, namely, 3NT. Ascorbate was also efficient at inhibiting the formation of 3NT by a dose-dependent anti-nitrosative effect and enabled the antioxidant action of nitrite.

  17. Oxidative damage of U937 human leukemic cells caused by hydroxyl radical results in singlet oxygen formation.

    PubMed

    Rác, Marek; Křupka, Michal; Binder, Svatopluk; Sedlářová, Michaela; Matušková, Zuzana; Raška, Milan; Pospíšil, Pavel

    2015-01-01

    The exposure of human cells to oxidative stress leads to the oxidation of biomolecules such as lipids, proteins and nuclei acids. In this study, the oxidation of lipids, proteins and DNA was studied after the addition of hydrogen peroxide and Fenton reagent to cell suspension containing human leukemic monocyte lymphoma cell line U937. EPR spin-trapping data showed that the addition of hydrogen peroxide to the cell suspension formed hydroxyl radical via Fenton reaction mediated by endogenous metals. The malondialdehyde HPLC analysis showed no lipid peroxidation after the addition of hydrogen peroxide, whereas the Fenton reagent caused significant lipid peroxidation. The formation of protein carbonyls monitored by dot blot immunoassay and the DNA fragmentation measured by comet assay occurred after the addition of both hydrogen peroxide and Fenton reagent. Oxidative damage of biomolecules leads to the formation of singlet oxygen as conformed by EPR spin-trapping spectroscopy and the green fluorescence of singlet oxygen sensor green detected by confocal laser scanning microscopy. It is proposed here that singlet oxygen is formed by the decomposition of high-energy intermediates such as dioxetane or tetroxide formed by oxidative damage of biomolecules.

  18. Hydroxyl radical induced by lipid in Maillard reaction model system promotes diet-derived N(ε)-carboxymethyllysine formation.

    PubMed

    Han, Lipeng; Li, Lin; Li, Bing; Zhao, Di; Li, Yuting; Xu, Zhenbo; Liu, Guoqin

    2013-10-01

    N(ε)-carboxymethyllysine (CML) is commonly found in food, and is considered as a potential hazard to human health. However, the effect of lipids on CML formation in Maillard reaction is still not clarified. In this study, the content of diet-derived CML and its key intermediates, epsilon-fructoselysine (FL) and glyoxal (GO), is determined with high performance liquid chromatography mass spectrum (HPLC-MS) in model system containing lipid compounds. According to the results, hydroxyl radical (OH) induced by Fenton reagent can promote the three pathways of CML formation. Moreover, in the Maillard reaction system, linoleic acid (Lin), oleic acid (Ole) and glycerol trioleate (Tri) can induce more OH·, which promotes CML formation. Their level of promoting CML formation is in the order of Ole>Lin>Tri. On the contrary, glycerol (Gly) can scavenge OH·, which inhibit the CML formation. Finally, it is proved that FL content and GO content decreases with heating time in model system, while CML content increases with heating time. Thus, it is concluded that in the Maillard reaction system lipids can induce more OH·, which promotes the conversion from FL and GO to CML. Our research may contribute to the development of inhibitory methods for diet-derived CML by scavenging OH·.

  19. Oxidizing Impact Induced by Mackinawite (FeS) Nanoparticles at Oxic Conditions due to Production of Hydroxyl Radicals.

    PubMed

    Cheng, Dong; Yuan, Songhu; Liao, Peng; Zhang, Peng

    2016-11-01

    Mackinawite (FeS) nanoparticles have been extensively tested for reducing contaminants under anoxic conditions, while the oxidizing impact induced by FeS under oxic conditions has been largely underestimated. In light of previous findings that hydroxyl radicals (·OH) can be produced from oxygenation of sediment Fe(II), herein we revealed that ·OH can be produced efficiently from FeS oxygenation at circumneutral conditions, yielding 84.7 μmol ·OH per g FeS. Much more ·OH was produced from the oxygenation of FeS compared with siderite, pyrite, and zerovalent iron nanoparticles under the same conditions. The oxidation of FeS was a surface-mediated process, in which O2 was transformed by the structural Fe(II) on FeS surface to ·OH with the generation of H2O2 intermediate. A small proportion of Fe(II) was regenerated from the reduction of Fe(III) by FeS and S(-II), but this proportion did not significantly contribute to ·OH production. We further validated that the ·OH produced from FeS oxygenation considerably contributed to the oxidation of arsenic. As the change of redox conditions from anoxic to oxic is common in both natural and artificial processes, our findings suggest that the oxidizing impact induced by FeS at oxic conditions should be concerned due to ·OH production.

  20. Hydrogen-Rich Water Ameliorates Total Body Irradiation-Induced Hematopoietic Stem Cell Injury by Reducing Hydroxyl Radical

    PubMed Central

    Xue, Xiaolei; Han, Xiaodan; Li, Yuan; Lu, Lu; Li, Deguan

    2017-01-01

    We examined whether consumption of hydrogen-rich water (HW) could ameliorate hematopoietic stem cell (HSC) injury in mice with total body irradiation (TBI). The results indicated that HW alleviated TBI-induced HSC injury with respect to cell number alteration and to the self-renewal and differentiation of HSCs. HW specifically decreased hydroxyl radical (∙OH) levels in the c-kit+ cells of 4 Gy irradiated mice. Proliferative bone marrow cells (BMCs) increased and apoptotic c-kit+ cells decreased in irradiated mice uptaken with HW. In addition, the mean fluorescence intensity (MFI) of γ-H2AX and percentage of 8-oxoguanine positive cells significantly decreased in HW-treated c-kit+ cells, indicating that HW can alleviate TBI-induced DNA damage and oxidative DNA damage in c-kit+ cells. Finally, the cell cycle (P21), cell apoptosis (BCL-XL and BAK), and oxidative stress (NRF2, HO-1, NQO1, SOD, and GPX1) proteins were significantly altered by HW in irradiated mouse c-kit+ cells. Collectively, the present results suggest that HW protects against TBI-induced HSC injury. PMID:28243358

  1. Mechanism of Augmentation of Organotin Decomposition by Ferripyochelin: Formation of Hydroxyl Radical and Organotin-Pyochelin-Iron Ternary Complex▿

    PubMed Central

    Sun, Guo-Xin; Zhong, Jian-Jiang

    2006-01-01

    Pyochelin (PCH), a kind of siderophore secreted by Pseudomonas aeruginosa, was recently found to have triphenyltin (TPT)-decomposing capacity. In this work, significant augmentation of TPT decomposition by ferripyochelin (FePCH), the chelating compound of PCH with iron, was demonstrated in Tris-HCl buffer (pH 8.0). The generation of hydroxyl radical (HO·) in the presence of FePCH was observed. Inhibition of HO· generation by adding catalase and HO· scavengers (methanol and dimethyl sulfoxide) decreased TPT decomposition, while an increase in HO· formation in the presence of H2O2 enhanced its decomposition. Our findings indicated that HO· generated in the reaction system was responsible for the enhanced TPT decomposition by FePCH versus PCH. The existence of the TPT-pyochelin-iron ternary complex was demonstrated by electron spray ionization-mass spectrometry, tandem mass spectrometry, and 1H nuclear magnetic resonance. On the basis of the above results, HO· produced in the presence of FePCH was deduced to be in close proximity to TPT and has more opportunity to attack the Sn-C bond, which resulted in the enhanced organotin decomposition. The information obtained may have considerable environmental significance. PMID:16997992

  2. Development of UV Optical Measurements of Nitric Oxide and Hydroxyl Radical at the Exit of High Pressure Gas Turbine Combustors

    NASA Technical Reports Server (NTRS)

    Liscinsky, D. S.; Knight, B. A.; Shirley, J. A.

    1998-01-01

    Measurements of nitric oxide (NO) and hydroxyl radical (OR) have been made in a laboratory flat flame at pressures up to 30 atm using line-of-sight resonant absorption. Data are reported at equivalence ratios of 0.98 and 1.3 and pressures of 1, 5, 10, 20 and 30 atm. The performance of the in-situ LTV absorption technique with assessed at these elevated pressures by comparing the measured absorption with those predicted by detailed theoretical spectroscopic models for NO and OH. Previous to this experiment the resonant models had not been verified at pressures greater than two atmospheres. Agreement within 25% was found between the measurements and predictions with only slight modification of the existing models for both NO and OH to account for line center shifting and pressure broadening. Continuum interference of hot oxygen (O2) on the NO absorption spectra was not significant in the interpretation of the data. The optical methods used in this study are distinct from laser-based diagnostics such as laser induced fluorescence and, hence, have the potential to provide independent verification of the laser-based measurements. The methodology is also of sufficient simplicity to be hardened into a portable optical measurement system that can be deployed in gas turbine engine test cells. A miniature fiber optic couple portable instrument is described.

  3. Effect of prenatal lead exposure on nigrostriatal neurotransmission and hydroxyl radical formation in rat neostriatum: dopaminergic-nitrergic interaction.

    PubMed

    Nowak, Przemysław; Szczerbak, Grazyna; Nitka, Dariusz; Kostrzewa, Richard M; Sitkiewicz, Tomasz; Brus, Ryszard

    2008-04-03

    The present study was designed to explore the role of ontogenetic lead (Pb(2+)) exposure on a putative dopaminergic-nitrergic interaction in the nigrostriatal pathway. Pregnant Wistar rats were given tap water containing 250-ppm lead acetate, for the duration of pregnancy, with regular tap water (without Pb(2+)) being substituted at birth. Control rats were derived from dams that consumed tap water throughout pregnancy, and had no exposure to Pb(2+) afterwards. At 12 weeks after birth in vivo microdialysis of the neostriatum was employed to demonstrate that maternal Pb(2+) exposure was without effect on the baseline dopamine (DA) microdialysate concentration as well as amphetamine (AMPH, 1.0mg/kg i.p.)-evoked release of striatal DA. Also, prenatal Pb(2+) exposure did not enhance AMPH- and 7-nitroindazole (neuronal nitric oxide synthase inhibitor) (7-NI, 20mg/kg i.p.)-induced hydroxyl radical (HO) formation in the striatum, as indicated by analysis of the salicylate spin-trap product 2,5-dihydroxybenzoic acid. However, in rats exposed prenatally to Pb(2+), the facilitatory effect of 7-NI on DA exocytosis was attenuated. On the basis of the current study we conclude that maternal Pb(2+) exposure distorts the dopaminergic-nitrergic interaction in the nigrostriatal pathway, but without involvement of reactive oxygen species (ROS).

  4. An iron-binding protein, Dpr, from Streptococcus mutans prevents iron-dependent hydroxyl radical formation in vitro.

    PubMed

    Yamamoto, Yuji; Poole, Leslie B; Hantgan, Roy R; Kamio, Yoshiyuki

    2002-06-01

    The dpr gene is an antioxidant gene which was isolated from the Streptococcus mutans chromosome by its ability to complement an alkyl hydroperoxide reductase-deficient mutant of Escherichia coli, and it was proven to play an indispensable role in oxygen tolerance in S. mutans. Here, we purified the 20-kDa dpr gene product, Dpr, from a crude extract of S. mutans as an iron-binding protein and found that Dpr formed a spherical oligomer about 9 nm in diameter. Molecular weight determinations of Dpr in solution by analytical ultracentrifugation and light-scattering analyses gave values of 223,000 to 292,000, consistent with a subunit composition of 11.5 to 15 subunits per molecule. The purified Dpr contained iron and zinc atoms and had an ability to incorporate up to 480 iron and 11.2 zinc atoms per molecule. Unlike E. coli Dps and two other members of the Dps family, Dpr was unable to bind DNA. One hundred nanomolar Dpr prevented by more than 90% the formation of hydroxyl radical generated by 10 microM iron(II) salt in vitro. The data shown in this study indicate that Dpr may act as a ferritin-like iron-binding protein in S. mutans and may allow this catalase- and heme-peroxidase-deficient bacterium to grow under air by limiting the iron-catalyzed Fenton reaction.

  5. Role of iron and superoxide for generation of hydroxyl radical, oxidative DNA lesions, and mutagenesis in Escherichia coli.

    PubMed

    Nunoshiba, T; Obata, F; Boss, A C; Oikawa, S; Mori, T; Kawanishi, S; Yamamoto, K

    1999-12-03

    We measured the generation of hydroxyl radical (OH(.)) and oxidative DNA lesions in aerobically grown Escherichia coli cells lacking in both superoxide dismutases (SodA SodB) and repressor of iron uptake (Fur) using electroparamagnetic resonance and gas chromatography-mass spectrometry with a selected-ion monitoring method. A specific signal corresponding to OH(.) generation and an increase in oxidative DNA lesions such as 7,8-dihydro-8-oxoguanine and 1,2-dihydro-2-oxoadenine were detected in the strain deficient in sodA sodB fur. We showed that iron metabolism deregulation in fur mutant produced a 2.5-fold iron overload. The sodA sodB fur strain was about 100-fold higher mutability than the wild-type strain. The mutation spectrum in the strain was found to induce GC --> TA and AT --> CG transversions predominantly. The hypermutability of the strain was suppressed by the tonB mutation which reduces iron transport. Thus, excess iron and excess superoxide were responsible for OH(.) generation, oxidative DNA lesion formation, and hypermutability in E. coli.

  6. Radiation protection of in vitro mammalian cells: effects of hydroxyl radical scavengers on the slopes and shoulders of survival curves

    SciTech Connect

    Ewing, D.; Walton, H.L. )

    1991-05-01

    We have tested several chemical compounds, characterized and widely used as hydroxyl radical (.OH) scavengers, for their effects on the radiation sensitivity of Chinese hamster V79 cells irradiated in air or nitrogen. Our purpose is to reexamine the proposed relationship between the level of protection and the rates at which the scavengers react with .OH. We found that the additives can have two apparently independent effects on the shape of survival curves: a reduction in sensitivity (i.e., 'protection,' a decrease in the value of k) and an increase in the size of the shoulder of the survival curve (an increase in the value of Dq). We measured intracellular scavenger concentrations, and, using these values in our analysis, we found that neither of the two effects is correlated with the rates at which the scavengers react with .OH. Although these results could mean that .OH do not cause lethal damage, the interpretation we believe most probably correct is that these scavengers protect in multiple ways. The protection would occur in addition to or instead of simple .OH removal.