Статті в журналах: "Oxygen-containing radicals"

1

Bersohn, Richard. "Radicals Containing Hydrogen, Carbon and Oxygen Atoms." Journal of the Chinese Chemical Society 49, no. 3 (June 2002): 291–300. http://dx.doi.org/10.1002/jccs.200200045.

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2

Elliot, A. John, Shahsultan Padamshi, and Jana Pika. "Free-radical redox reactions of uranium ions in sulphuric acid solutions." Canadian Journal of Chemistry 64, no. 2 (February 1, 1986): 314–20. http://dx.doi.org/10.1139/v86-053.

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The radiolytic reduction of uranyl ions in degassed sulphuric acid solutions containing various organic solutes was studied. It was shown that while ĊOOH, CO2−, and α-hydroxy-alkyl radicals reduced uranyl ions, the β-hydroxy-alkyl radicals and those derived from gluconic acid could not affect the reduction. The oxidation of uranium(IV) by hydrogen peroxide at pH 0.7 involves hydroxyl radicals in a chain mechanism but at pH 2.0 the oxidation proceeds by a non-radical reaction pathway. From the enhancement of the rate of oxidation of uranium(IV) by oxygen in the presence of 2-propanol, a mechanism involving the perhydroxyl radical, which reconciles earlier published data on kinetics and oxygen tracer studies, is proposed for the oxygen-uranium(IV) reactions.

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3

Morgan, Christopher G., Mark M. Gleason, and Ronald Vane. "Quantification of Contaminant Removal by Evactron Cleaning Using Quartz Crystal Thickness Monitors." Microscopy Today 15, no. 5 (September 2007): 22–25. http://dx.doi.org/10.1017/s1551929500061198.

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Hydrocarbon (HC) contamination is a persistent problem for users of electron microscopes (EMs), often leading to image distortion and interference with nanoprobing. The Evactron De-Contaminator (D-C) has been available for HC contamination removal in EMs since 1999. The Evactron D-C uses low power radio frequency (RF) generated plasma in order to produce oxygen radicals that clean the EM. The Oxygen Radical Source (ORS) is attached to the EM chamber, and a controlled leak of oxygen containing gas such as room air is passed through the plasma in order to produce oxygen radicals. The oxygen radicals chemically react with the HCs to form volatile oxidation products such as H2O, CO and CO2. These volatile compounds are pumped out of the EM chamber.

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4

Orlov, Yu D., E. M. Chernova, and V. V. Turovtsev. "Formation enthalpies of organic oxygen-containing heterocyclic radicals." Chemistry of Heterocyclic Compounds 47, no. 1 (April 2011): 29–35. http://dx.doi.org/10.1007/s10593-011-0716-1.

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5

Bogachev, A. A., L. S. Kobrina, and G. G. Yakobson. "The interaction of polyfluoroaromatic compounds with oxygen containing radicals." Journal of Fluorine Chemistry 29, no. 1-2 (August 1985): 143. http://dx.doi.org/10.1016/s0022-1139(00)83379-5.

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6

Ji, Xun, Omar M. Khdour, and Sidney M. Hecht. "Multifunctional radical quenchers as potential therapeutic agents for the treatment of mitochondrial dysfunction." Future Medicinal Chemistry 11, no. 13 (July 2019): 1605–24. http://dx.doi.org/10.4155/fmc-2018-0481.

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Mitochondrial dysfunction is associated with a wide range of human diseases, including neurodegenerative diseases, and is believed to cause or contribute to the etiology of these diseases. These disorders are frequently associated with increased levels of reactive oxygen species. One of the design strategies for therapeutic intervention involves the development of novel small molecules containing redox cores, which can scavenge reactive oxygen radicals and selectively block oxidative damage to the mitochondria. Presently, we describe recent research dealing with multifunctional radical quenchers as antioxidants able to scavenge reactive oxygen radicals. The review encompasses ubiquinone and tocopherol analogs, as well as novel pyri(mi)dinol derivatives, and their ability to function as protective agents in cellular models of mitochondrial diseases.

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7

Renaud, Philippe, Alice Beauseigneur, Andrea Brecht-Forster, Barbara Becattini, Vincent Darmency, Sarkunam Kandhasamy, Florian Montermini, et al. "Boron: A key element in radical reactions." Pure and Applied Chemistry 79, no. 2 (January 1, 2007): 223–33. http://dx.doi.org/10.1351/pac200779020223.

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Boron derivatives are becoming key reagents in radical chemistry. Here, we describe reactions where an organoboron derivative is used as a radical initiator, a chain-transfer reagent, and a radical precursor. For instance, B-alkylcatecholboranes, easily prepared by hydroboration of alkenes, represent a very efficient source of primary, secondary, and tertiary alkyl radicals. Their very high sensitivity toward oxygen- and heteroatom-centered radicals makes them particularly attractive for the development of radical chain processes such as conjugate addition, allylation, alkenylation, and alkynylation. Boron derivatives have also been used to develop an attractive new procedure for the reduction of radicals with alcohols and water. The selected examples presented here demonstrate that boron-containing reagents can efficiently replace tin derivatives in a wide range of radical reactions.

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8

Hu, Xiao-Qiang, Zi-Kui Liu, and Wen-Jing Xiao. "Radical Carbonylative Synthesis of Heterocycles by Visible Light Photoredox Catalysis." Catalysts 10, no. 9 (September 14, 2020): 1054. http://dx.doi.org/10.3390/catal10091054.

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Visible light photocatalytic radical carbonylation has been established as a robust tool for the efficient synthesis of carbonyl-containing compounds. Acyl radicals serve as the key intermediates in these useful transformations and can be generated from the addition of alkyl or aryl radicals to carbon monoxide (CO) or various acyl radical precursors such as aldehydes, carboxylic acids, anhydrides, acyl chlorides or α-keto acids. In this review, we aim to summarize the impact of visible light-induced acyl radical carbonylation reactions on the synthesis of oxygen and nitrogen heterocycles. The discussion is mainly categorized based on different types of acyl radical precursors.

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9

Beckwith, ALJ, and SA Glover. "Determination of the Rates of Ring-Closure of Oxygen-Containing Analogs of Hex-5-Enyl Radical by Kinetic Electron Spin Resonance Spectroscopy." Australian Journal of Chemistry 40, no. 1 (1987): 157. http://dx.doi.org/10.1071/ch9870157.

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The hex-5-enyl (1), 3-oxahex-5-enyl (6), 2-oxahex-5-enyl (9) and 2,2-dimethylbut-3- enoyloxymethyl (13) radicals have been generated by interaction of the corresponding bromides with trialkyltin or trialkylgermanium radicals, and their rate constants and activation parameters for cyclization have been determined by kinetic e.s.r . spectroscopy. The 3-oxa species (6) undergo 1,5-ring closure more rapidly than does hex-5-enyl radical (1) because of favourable stereoelectronic factors. Spectral evidence has been obtained for restricted rotation about the O-CH2* bond in the 2-oxa radical (9) as a consequence of which its ring closure is relatively slow. Similarly, 1,5-ring closure of the ester derived radical (13) is slow because of unfavourable conformational effects arising from restricted rotation about the CO-O bond. The radical (22) formed from allyl bromoacetate does not undergo ring closure. Spectral data have been obtained for various radicals (16), (19), (23), (24) formed by intermolecular addition.

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10

Sehirli, Ahmet Ozer, Serkan Sayıner, Ugochukwu Chukwunyere, and Nedime Serakinci. "Role of Melatonin in Angiotensin and Aging." Molecules 26, no. 15 (July 31, 2021): 4666. http://dx.doi.org/10.3390/molecules26154666.

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The cellular utilization of oxygen leads to the generation of free radicals in organisms. The accumulation of these free radicals contributes significantly to aging and several age-related diseases. Angiotensin II can contribute to DNA damage through oxidative stress by activating the NAD(P)H oxidase pathway, which in turn results in the production of reactive oxygen species. This radical oxygen-containing molecule has been linked to aging and several age-related disorders, including renal damage. Considering the role of angiotensin in aging, melatonin might relieve angiotensin-II-induced stress by enhancing the mitochondrial calcium uptake 1 pathway, which is crucial in preventing the mitochondrial calcium overload that may trigger increased production of reactive oxygen species and oxidative stress. This review highlights the role and importance of melatonin together with angiotensin in aging and age-related diseases.

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11

Siriwardhana, Nalin, K. W. Lee, Y. J. Jeon, S. H. Kim, and J. W. Haw. "Antioxidant Activity of Hizikia fusiformis on Reactive Oxygen Species Scavenging and Lipid Peroxidation Inhibition." Food Science and Technology International 9, no. 5 (October 2003): 339–46. http://dx.doi.org/10.1177/1082013203039014.

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Water and organic extracts (diethyl ether, chloroform, ethyl acetate, acetone, ethanol and methanol) obtained from Hizikia fusiformis were screened on reactive oxygen species (ROS) scavenging assays (1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide anion, hydrogen peroxide and hydroxyl radical) and lipid peroxidation (inhibition of linoleic acid oxidation) inhibitory assays. Water, methanol and ethanol extracts showed significant ROS radical scavenging activities. Water extracts showed high scavenging activities on hydrogen peroxide (around 76%) and DPPH radicals (around 75%) while it presented a moderate scavenging activity on hydroxyl radicals (around 54%). Comparatively higher ROS scavenging activities were recorded in hydroxyl radical and DPPH scavenging assays. DPPH radical scavenging activities were well correlated with the polyphenolic content. ROS scavenging and lipid peroxidation inhibition activities indicated that H. fusiformis might be a valuable natural antioxidative source containing both water and fatsoluble antioxidative components.

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12

Šnyrychová, Iva, and Éva Hideg. "The first application of terephthalate fluorescence for highly selective detection of hydroxyl radicals in thylakoid membranes." Functional Plant Biology 34, no. 12 (2007): 1105. http://dx.doi.org/10.1071/fp07150.

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Possibilities and limitations of the detection of hydroxyl radicals via the conversion of terephthalate (TPA) into the strongly fluorescent hydroxyterephthalate were investigated in order to adapt this method for chlorophyll-containing samples. Using model chemical sources of various reactive oxygen species, we confirmed that TPA detects hydroxyl radicals very sensitively, but is not reactive to either hydrogen peroxide or superoxide radicals. As a new result, we showed that the conversion of TPA to hydroxyterephthalate cannot be induced by singlet oxygen, which may be produced in photosynthetic systems under stress. Until now, the TPA method has not been used in photosynthesis research, so necessary adaptations to minimise the effects of chlorophyll and buffering sugars on hydroxyl radical detection were also explored and optimal conditions for using the method in thylakoid preparations are suggested. Anticipating further plant physiology applications, usefulness of the TPA method was tested in a wider range of pH than reported earlier. To demonstrate that this simple and highly specific method can be used as an alternative approach for the detection of hydroxyl radicals in plant samples, we measured these radicals in isolated thylakoid membranes exposed to 312 nm ultraviolet radiation.

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13

Silaev, M. M. "Competition Kinetics of the Nonbranched-Chain Addition of Free Radicals to Olefins, Formaldehyde, and Oxygen." International Journal of Chemical Engineering 2011 (2011): 1–19. http://dx.doi.org/10.1155/2011/830610.

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Five reaction schemes are suggested for the initiated nonbranched-chain addition of free radicals to the multiple bonds of alkenes, formaldehyde, and oxygen. The schemes include reactions competing with chain propagation through a reactive free radical. The chain evolution stage in these schemes involves three or four types of free radicals. One of them— , , , , or —is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length. Based on the suggested schemes, nine rate equations containing one to three parameters to be determined directly are set up using quasi-steady-state treatment. These equations provide good fits for the nonmonotonic (peaking) dependences of the formation rates of the molecular addition products (1 : 1 adducts) on the concentration of the unsaturated component in liquid homogeneous binary systems consisting of a saturated component (hydrocarbon, alcohol, etc.) and an unsaturated component (olefin, formaldehyde, or dioxygen). The unsaturated compound in these systems is both a reactant and an autoinhibitor generating low-reactive free radicals. A similar kinetic description is applicable to nonbranched-chain free-radical hydrogen oxidation. The energetics of the key radical-molecule reactions is considered.

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14

Narsito, Narsito, Sri Juari Santosa, and Setya Lastuti. "PHOTO-REDUCTION KINETICS OF MnO₂ IN AQUATIC ENVIRONMENTS CONTAINING HUMIC ACIDS." Indonesian Journal of Chemistry 8, no. 1 (June 17, 2010): 37–41. http://dx.doi.org/10.22146/ijc.21645.

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The kinetics of photo-reduction of manganese(IV) oxide, MnO2 in aqueous medium, in the presence of humic acid has been investigated, including the possibility for the involvement of such radicals in the reduction. Results showed that in aqueous medium, the efficiency of the photo-reduction of MnO2 producing a soluble ionic Mn(II) was governed strongly by an internal electron transfer within an intermediate of HA-MnO2 anion complex, resulted in the chemical adsorption of humic acid on MnO2 surface. It was observed that under solar radiation and atmosphere containing oxygen, the rate of MnO2 reduction increased considerably, by factors of about 46 and 2 respectively. Moreover, there was evidence that some radicals certainly played a role in the photo-reduction of MnO2, since radical scavenger addition significantly decreased the reduction efficiency of MnO2. In the present of an excess of propanol-2, however, which was expected to remove all OH radicals present, only about 60 % decrease in reduction efficiency were observed, suggesting that radicals other than OH radical are involved in the reduction of MnO2. It was observed further that the presence of iron(III) in MnO2 up to 1 % (w/w) did not alter the reduction efficiency of MnO2. Keywords: MnO2 kinetics, photo-reduction, aquatic, humic acids

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15

Kuz'min, V. A., P. F. Pluzhnikov, and P. P. Levin. "Kinetics of the quenching of triplet exciplexes containing contact radical-ion pairs by oxygen and radicals." Bulletin of the Academy of Sciences of the USSR Division of Chemical Science 37, no. 6 (June 1988): 1256–59. http://dx.doi.org/10.1007/bf00961949.

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16

Iwahashi, H., T. Ishii, R. Sugata, and R. Kido. "Superoxide dismutase enhances the formation of hydroxyl radicals in the reaction of 3-hydroxyanthranilic acid with molecular oxygen." Biochemical Journal 251, no. 3 (May 1, 1988): 893–99. http://dx.doi.org/10.1042/bj2510893.

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Superoxide dismutase (SOD) enhanced the formation of hydroxyl radicals, which were detected by using the e.s.r. spin-trapping technique, in a reaction mixture containing 3-hydroxyanthranilic acid (or p-aminophenol), Fe3+ ions, EDTA and potassium phosphate buffer, pH 7.4. The hydroxyl-radical formation enhanced by SOD was inhibited by catalase and desferrioxamine, and stimulated by EDTA and diethylenetriaminepenta-acetic acid, suggesting that both hydrogen peroxide and iron ions participate in the reaction. The hydroxyl-radical formation enhanced by SOD may be considered to proceed via the following steps. First, 3-hydroxyanthranilic acid is spontaneously auto-oxidized in a process that requires molecular oxygen and yields superoxide anions and anthranilyl radicals. This reaction seems to be reversible. Secondly, the superoxide anions formed in the first step are dismuted by SOD to generate hydrogen peroxide and molecular oxygen, and hence the equilibrium in the first step is displaced in favour of the formation of superoxide anions. Thirdly, hydroxyl radicals are generated from hydrogen peroxide through the Fenton reaction. In this Fenton reaction Fe2+ ions are available since Fe3+ ions are readily reduced by 3-hydroxyanthranilic acid. The superoxide anions do not seem to participate in the reduction of Fe3+ ions, since superoxide anions are rapidly dismuted by SOD present in the reaction mixture.

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17

Sicilia, Emilia, Francesco P. Di Maio, and Nino Russo. "Heats of formation of oxygen-containing radicals from local spin density computations." Journal of Physical Chemistry 97, no. 2 (January 1993): 528–30. http://dx.doi.org/10.1021/j100104a043.

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18

Wu, Zong-Hua, Masashi Sumimoto, and Hiroo Tanaka. "Generation of Oxygen-Containing Radicals in the Aqueous Media of Mechanical Pulping." Journal of Wood Chemistry and Technology 15, no. 1 (February 1995): 27–42. http://dx.doi.org/10.1080/02773819508009498.

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19

Kelley, Matthew a., Taylor Thibeaux, Valeria Hebert, Stephania a. Cormier, Slawo Lomnicki, Barry Dellinger, and Tammy R. Dugas. "Model Particulate Matter Containing Persistent Free Radicals Exhibit Reactive Oxygen Species Production." Free Radical Biology and Medicine 51 (November 2011): S134. http://dx.doi.org/10.1016/j.freeradbiomed.2011.10.280.

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20

Allayarov, S. R., I. M. Barkalov, and Yu L. Bakhmutov. "Formation of long-lived radicals in radiolysis of oxygen-containing organofluorine compounds." Bulletin of the Academy of Sciences of the USSR Division of Chemical Science 37, no. 6 (June 1988): 1102–6. http://dx.doi.org/10.1007/bf00961909.

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21

Ferrari, Roberto, C. Ceconi, S. Curello, A. Cargnoni, O. Alfieri, A. Pardini, P. Marzollo, and O. Visioli. "Oxygen free radicals and myocardial damage: Protective role of thiol-containing agents." American Journal of Medicine 91, no. 3 (September 1991): S95—S105. http://dx.doi.org/10.1016/0002-9343(91)90291-5.

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22

Gong, D. H., B. Turner, K. R. Bhaskar, and J. T. Lamont. "Lipid binding to gastric mucin: protective effect against oxygen radicals." American Journal of Physiology-Gastrointestinal and Liver Physiology 259, no. 4 (October 1, 1990): G681—G686. http://dx.doi.org/10.1152/ajpgi.1990.259.4.g681.

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Gastric mucus forms a viscous gel overlying the gastric mucosa and is thought to protect the underlying mucosa from noxious agents such as acid, proteases, and bile salts. A common property of mucin, the principal glycoprotein in mucous secretions, is its ability to bind lipids. The purpose of this study was to determine if lipids bound to gastric mucin protect the mucin from oxygen radical attack. Pig gastric mucin, partially purified by Sepharose 4B gel chromatography, was found to contain large amounts of free fatty acids and cholesterol as well as lesser amounts of sphingomyelin and phospholipids. Purified mucin obtained by density-gradient ultracentrifugation in a CsCl gradient contained only trace amounts of fatty acids but no other lipids. Exposure to the oxygen radical-generating system iron/ascorbate caused a marked reduction in viscosity of purified mucin but did not affect partially purified mucin, suggesting that bound lipids shielded the mucin from attack by oxygen radicals. Using discontinuous sucrose-gradient ultracentrifugation in the presence of liposomes containing [3H]palmitic acid, we demonstrated that mucin is capable of binding fatty acids. We also observed a striking increase in solution viscosity of gastric mucin at low pH, a feature that might contribute to the ability of mucin to form a protective diffusion barrier for the underlying epithelium.

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23

Iyer, Jayant, Isha Saraf, Andrew Ray, Michael Brunsteiner, and Amrit Paudel. "Assessment of Diverse Solid−State Accelerated Autoxidation Methods for Droperidol." Pharmaceutics 14, no. 6 (May 24, 2022): 1114. http://dx.doi.org/10.3390/pharmaceutics14061114.

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The present study aimed to investigate methods for accelerating autoxidation of crystalline drugs in the solid-state that can potentially predict real−time stability. Solid droperidol (DPD) was selected as the model drug. A common free−radical initiator, 2,2′−azobisisobutyronitrile (AIBN), was used to induce autoxidation in solutions. AIBN decomposes at elevated temperatures to yield carbon−centred cyano−isopropyl free radicals that can auto−oxidize neighboring drug molecules. Although the reaction of AIBN is relatively straightforward in solution, it is less so in solids. In this study, we used solid AIBN mixed with DPD powder in the presence and absence of pressurized oxygen headspace. Samples were prepared directly in the form of binary mixtures with DPD and additionally in the form of powder compact/pellet with DPD. The main challenge in carrying out the reaction was related to the preservation of AIBN at elevated temperatures due to the disintegration of the pellet containing the latter. A commercially available free−radical coated silica particle (i.e., 2,2,6,6−tetramethyl−1−piperinyloxy (TEMPO) or (SiliaCATTM TEMPO)) was tested as a potential stressor, but with limited success to induce autoxidation. The most valuable results were obtained when a physical mixture of pre−milled PVP K−60 containing free radicals and DPD was exposed to elevated oxygen−temperature conditions, which yielded significant degradation of DPD. The study highlights the practical challenges for conducting accelerated solid−state stress studies to assess the autoxidation susceptibility of drugs using traditional free−radical initiators and presents a proof of application of milled PVP with free−radical as a potential alternative.

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24

Rusakova, Natalia P., Alexei V. Kotomin, Yuri D. Orlov, and Vladimir V. Turovtsev. "ELECTRON STRUCTURE OF RADICALS OF SULFOXYLIC ACID ESTERS." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 62, no. 10 (October 29, 2019): 96–102. http://dx.doi.org/10.6060/ivkkt.20196210.5964.

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The density functional theory B3LYP/6-311++G(3df,3pd) has been used to optimize the geometry of homologues of a series of sulfoxylic acid ester radicals and to obtain the electron density distributions of the first nine compounds. The hydrogen bond presented in the initial molecules of the unbranched esters of sulfoxylic acid between the hydrogen of the second carbon atom of the alkyl chain (from the ester bond) and the oxygen of the hydroxyl group of the sulfur-containing fragment (-C(Н)H-CH2-O-S-ОН) and the corresponding cycle are not observed in the radicals. The fragmentation of the structures into topological groups of CH3, CH2, and (-O-S-O)● has been proposed and their electron integral characteristics are presented including charges, unpaired electron density, energy, and volume. The steric effect of the fragment (-O-S-O)● has been established and its inductive effect has been considered based on the groups charge parameters changes triggered by an increase in the hydrocarbon chain. The scale of group electronegativities of the studied homologues has been constructed by comparing the charges of topological groups. The fact that the radical center corresponds to the fragment (-O-S-O)● has been demonstrated by the spin density delocalization results (having the largest fraction on the sulfur atom (0.57), slightly less fraction on the oxygen atom with a free valence (0.32) and an insignificant fraction on oxygen atom using the ether bond (0.10)). The increment value of the total energy contributed by the CH2 group of each subsequent homologue of the series under the study has been estimated. It is 103260 kJ/mol. The evaluation of the “standard” value of the groups’ total electron energy and the use of their relative energy (ΔE(R)) for comparing with ΔE(R) of molecules and radicals of other homologous series have been described. A decrease in the volumes of the two closest to the sulfur-containing fragment CH2 groups caused by an outflow of electron density from them toward the fragment (-O-S-O)● has been noted.

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25

Mattsson, Cecilia, Stefan L. Marklund, and Sten Hellström. "Application of Oxygen Free Radical Scavengers to Diminish the Occurrence of Myringosclerosis." Annals of Otology, Rhinology & Laryngology 106, no. 6 (June 1997): 513–18. http://dx.doi.org/10.1177/000348949710600613.

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The present study was designed to establish whether or not an increased production of oxygen-derived free radicals is involved in the causation of myringosclerosis. Sclerotic lesions in the tympanic membrane were experimentally elicited by keeping rats with perforated tympanic membranes in an atmosphere containing roughly 40% oxygen. The animals were treated daily with a solution containing either copper zinc-supcroxide dismutase plus catalase, deferoxamine, or copper sulfate plus iron chloride, applied to the traumatized area. After 1 week the extension of myringosclerotic plaques was determined otomicroscopically. The pars tensa and pars flaccida were then dissected free and prepared for light microscopic studies. The results showed that treatment with copper zinc-superoxide dismutase plus catalase and deferoxamine inhibited or reduced the development of myringosclerosis, whereas die ears treated with copper sulfate plus iron chloride appeared unaffected. Consequently, the findings support the hypothesis that the formation of oxygen free radicals contributes significantly to the development of myringosclerosis.

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26

Huseynova, B. A., N. F. Gafarova, and E. A. Bekhmetova. "Study of acidic oxygen-containing and nitrogenous compounds isolated from 150–350 °C fraction of deep-water Gunashli field oil." Azerbaijan Oil Industry, no. 10 (October 15, 2020): 51–53. http://dx.doi.org/10.37474/0365-8554/2020-10-51-53.

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The article presents the results of studies on the structural-group composition of acidic oxygen-containing and nitrogenous compounds isolated from the 150–350 oC fraction of the deep-water oil of Gunashli field. The oil is light, low sulfur, paraffinic, rich in light fractions, the acid number is 1.01 mg KOH/g, the total content of acidic oxygen-containing compounds is 0.17 %, and total nitrogen is 0.11 % by weight. The acid number of the 150–350 oC fraction from the same oil is 242.3 mg KOH/g. Acidic oxygen-containing compounds isolated from this fraction with a yield of 0.19 %, nitrogen-containing 0.145 % mass. The structural-group composition of the isolated concentrates of acidic oxygen and nitrogen-containing compounds was studied by PMR spectroscopy. It was defined that the acidic oxygen-containing compounds more than 2/3 belong to the naphthenic-paraffin series. Nitrogen compounds are for 78 % composed of aminocompounds with naphthenic-paraffinic radicals and aromatic homologues (22 %). They can be used for the synthesis of metal corrosion inhibitors, additives for lubricating oils and other valuable products.

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27

Daval, Jean-Luc, Jean-François Ghersi-Egea, Jean Oillet, and Violette Koziel. "A Simple Method for Evaluation of Superoxide Radical Production in Neural Cells under Various Culture Conditions: Application to Hypoxia." Journal of Cerebral Blood Flow & Metabolism 15, no. 1 (January 1995): 71–77. http://dx.doi.org/10.1038/jcbfm.1995.8.

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To evaluate the potential deleterious influence of oxygen-derived free radicals following hypoxia in a model of primary culture of neurons obtained from the fetal rat brain, superoxide radicals were measured as a function of time in the extracellular medium. Neuronal cells were grown for 8 days in the presence or absence of serum, then incubated in a buffered Krebs–Ringer solution containing 60 μ M acetyl-cytochrome c. The rate of superoxide radical formation was quantified spectrophotometrically by measuring the specific reduction of acetyl-cytochrome c. Under normoxic conditions (95% air-5% CO2), basal production of superoxide that increased with time was recorded. It was significantly more pronounced in cells grown in serum-free medium. Under both culture conditions, acute hypoxia (95% N2–5% CO2) for 6 h increased superoxide radical amounts in the extracellular medium, and they were still enhanced 3 h after reoxygenation. The addition of superoxide dismutase to the incubating medium abolished the detection of superoxide radicals. The present study describes a new reliable method for superoxide radical measurement in cells in vitro and demonstrates hypoxia/reoxygenation-induced overproduction of superoxide in cultured neurons that may account for cell injury.

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28

Reece, Steven Y., Justin M. Hodgkiss, JoAnne Stubbe, and Daniel G. Nocera. "Proton-coupled electron transfer: the mechanistic underpinning for radical transport and catalysis in biology." Philosophical Transactions of the Royal Society B: Biological Sciences 361, no. 1472 (July 17, 2006): 1351–64. http://dx.doi.org/10.1098/rstb.2006.1874.

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Charge transport and catalysis in enzymes often rely on amino acid radicals as intermediates. The generation and transport of these radicals are synonymous with proton-coupled electron transfer (PCET), which intrinsically is a quantum mechanical effect as both the electron and proton tunnel. The caveat to PCET is that proton transfer (PT) is fundamentally limited to short distances relative to electron transfer (ET). This predicament is resolved in biology by the evolution of enzymes to control PT and ET coordinates on highly different length scales. In doing so, the enzyme imparts exquisite thermodynamic and kinetic controls over radical transport and radical-based catalysis at cofactor active sites. This discussion will present model systems containing orthogonal ET and PT pathways, thereby allowing the proton and electron tunnelling events to be disentangled. Against this mechanistic backdrop, PCET catalysis of oxygen–oxygen bond activation by mono-oxygenases is captured at biomimetic porphyrin redox platforms. The discussion concludes with the case study of radical-based quantum catalysis in a natural biological enzyme, class I Escherichia coli ribonucleotide reductase. Studies are presented that show the enzyme utilizes both collinear and orthogonal PCET to transport charge from an assembled diiron-tyrosyl radical cofactor to the active site over 35 Å away via an amino acid radical-hopping pathway spanning two protein subunits.

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29

Holmes, John L., Fred P. Lossing, and Paul M. Mayer. "Heats of formation of oxygen-containing organic free radicals from appearance energy measurements." Journal of the American Chemical Society 113, no. 26 (December 1991): 9723–28. http://dx.doi.org/10.1021/ja00026a002.

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30

O'Connell, M., B. Halliwell, C. P. Moorhouse, O. I. Aruoma, H. Baum, and T. J. Peters. "Formation of hydroxyl radicals in the presence of ferritin and haemosiderin. Is haemosiderin formation a biological protective mechanism?" Biochemical Journal 234, no. 3 (March 15, 1986): 727–31. http://dx.doi.org/10.1042/bj2340727.

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Horse spleen and human spleen ferritins increase the formation of hydroxyl radicals (OH) at both pH 4.5 and pH 7.4 in reaction mixtures containing ascorbic acid and H2O2. The generation of OH is inhibited by the chelator desferrioxamine. Human spleen haemosiderin also accelerates OH generation in identical reaction mixtures, but is far less effective (on a unit iron basis) than ferritin under all reaction conditions. It is proposed that conversion of ferritin into haemosiderin in iron overload is biologically advantageous in that it decreases the ability of iron to promote oxygen-radical reactions.

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31

Denisov, E. T., and T. G. Denisova. "Polar and solvation effects in reactions of oxygen atoms and hydroxyl and alkoxyl radicals with oxygen-containing compounds." Russian Chemical Bulletin 43, no. 1 (January 1994): 29–34. http://dx.doi.org/10.1007/bf00699130.

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32

Qiu, Maoqin, Zhangxian Chen, Zeheng Yang, Wenming Li, Yuan Tian, Weixin Zhang, Yishu Xu, and Hansong Cheng. "ZnMn2O4 nanorods: an effective Fenton-like heterogeneous catalyst with t2g3eg1 electronic configuration." Catalysis Science & Technology 8, no. 10 (2018): 2557–66. http://dx.doi.org/10.1039/c8cy00436f.

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The t_2g³e_g¹ electron configuration of Mn benefits the Fenton-like spinel ZnMn₂O₄ nanorod catalyst by promoting the creation of oxygen-containing radicals.

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33

Wang, Rui, Chen-Loung Chen, and Josef S. Gratzl. "Ozonation of pine kraft lignin in alkaline solution. Part 1: Ozonation, characterization of kraft lignin and its ozonated preparations." Holzforschung 58, no. 6 (October 1, 2004): 622–30. http://dx.doi.org/10.1515/hf.2004.116.

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Abstract Pine kraft lignin was purified to obtain a kraft lignin preparation (KL) with weight average molecular mass (Mw) of 5500. The KL was then ozonated with an ozone-air stream containing 2–2.5% of ozone in 0.1 M sodium hydroxide solution to prepare ozonated kraft lignin preparations with ozone consumption of 10, 25, 30 and 40% per KL; Oz-10-KL, Oz-25-KL, Oz-30-KL and Oz-40-KL, respectively. The pH of reaction mixture was decreased with increasing ozone consumption, while the carboxylic acid content and the Mw of resulting ozonated lignins increase with increasing ozone consumption. The KL and its ozonated preparations were then characterized by elemental composition, functional group analysis, molecular mass distribution and nitrobenzene-K4MnO4 oxidation. The results showed that the KL extensively undergoes oxidative cleavage of both side chains and aromatic moieties without decrease in the Mw as well as dehydrogenationive coupling of phenolic degraded fragments by active oxygen radical species, such as hydroperoxyl and hydroxyl radicals. The formation of these active oxygen radical species are produced by way of a series of reactions initiated by the reaction of ozone with hydroxide anions at pH range of 12.4–10.5, producing superoxide (-O2•) and hydroperoxyl (HOO•) radicals.

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34

M. Silaev, Michael. "Kinetics of Free-Radical Addition Processes by the Nonbranched-Chain Mechanism." Journal of Advance Research in Applied Science (ISSN: 2208-2352) 3, no. 10 (October 31, 2016): 01–19. http://dx.doi.org/10.53555/nnas.v3i10.645.

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Five reaction schemes are suggested for the initiated nonbranched-chain addition of free radicals to the multiple bonds of the unsaturated compounds. The proposed schemes include the reaction competing with chain propagation reactions through a reactive free radical. The chain evolution stage in these schemes involves three or four types of free radicals. One of them is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length. Based on the suggested schemes, nine rate equations (containing one to three parameters to be determined directly) are deduced using quasi-steady-state treatment. These equations provide good fits for the nonmonotonic (peaking) dependences of the formation rates of the molecular products (1:1 adducts) on the concentration of the unsaturated component in binary systems consisting of a saturated component (hydrocarbon, alcohol, etc.) and an unsaturated component (alkene, allyl alcohol, formaldehyde, or dioxygen). The unsaturated compound in these systems is both a reactant and an autoinhibitor generating low-reactive free radicals. A similar kinetic description is applicable to the nonbranched-chain process of the free-radical hydrogen oxidation, in which the oxygen with the increase of its concentration begins to act as an oxidation autoingibitor (or an antioxidant). The energetics of the key radical-molecule reactions is considered.

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35

Sicilia, E., F. P. Di Maio, and N. Russo. "Determination of the heat of formation of oxygen containing radicals using density functional theory." Journal of Molecular Structure: THEOCHEM 310 (July 1994): 13–16. http://dx.doi.org/10.1016/s0166-1280(09)80078-x.

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36

Yoshitomi, Toru, Kazuhiro Kuramochi, Long Binh Vong, and Yukio Nagasaki. "Development of nitroxide radicals–containing polymer for scavenging reactive oxygen species from cigarette smoke." Science and Technology of Advanced Materials 15, no. 3 (June 2014): 035002. http://dx.doi.org/10.1088/1468-6996/15/3/035002.

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37

Nishizaki, Daisuke, and Hideo Iwahashi. "Oxygen-Centered Radicals Formed in the Reaction Mixtures Containing Chloroiron Tetraphenylporphyrin, Iodosylbenzene, and Ethanol." Inorganic Chemistry 56, no. 21 (October 10, 2017): 13166–73. http://dx.doi.org/10.1021/acs.inorgchem.7b01949.

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38

Sicilia, E., F. P. Di Maio, and N. Russo. "Determination of the heat of formation of oxygen containing radicals using density functional theory." Journal of Molecular Structure 310 (July 1994): 13–16. http://dx.doi.org/10.1016/s0022-2860(10)80050-x.

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39

Beckwith, Athelstan L. J., and Steven Brumby. "An electron spin resonance investigation of free radicals with oxygen- and sulphur-containing substituents." Journal of the Chemical Society, Perkin Transactions 2, no. 12 (1987): 1801. http://dx.doi.org/10.1039/p29870001801.

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40

Denisova, T. G., and E. T. Denisov. "Kinetic parameters of the cyclization and decyclization reactions of nitrogen- and oxygen-containing radicals." Kinetics and Catalysis 46, no. 1 (January 2005): 1–9. http://dx.doi.org/10.1007/s10975-005-0001-3.

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41

Denisova, T. G., and E. T. Denisov. "Kinetic parameters of the cyclization and decyclization reactions of nitrogen- and oxygen-containing radicals." Kinetics and Catalysis 46, no. 1 (January 2005): 1–9. http://dx.doi.org/10.1007/s10975-005-0027-6.

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42

Diaz, P. T., Z. W. She, W. B. Davis, and T. L. Clanton. "Hydroxylation of salicylate by the in vitro diaphragm: evidence for hydroxyl radical production during fatigue." Journal of Applied Physiology 75, no. 2 (August 1, 1993): 540–45. http://dx.doi.org/10.1152/jappl.1993.75.2.540.

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There is increasing evidence that oxygen-derived free radicals produced during strenuous work by the diaphragm may contribute to diaphragm fatigue and/or injury. However, the precise identity of these oxygen radicals remains unknown, inasmuch as oxygen free radicals are extremely short lived and their detection in biologic systems is quite difficult. There is recent evidence that the salicylate-trapping method may be a useful means of monitoring tissue production of hydroxyl radical (.OH). This method is predicated on the fact that salicylate's phenolic ring can be attacked by .OH at the 3 or 5 position to yield 2,3- or 2,5-dihydroxybenzoic acid (DHB). These metabolites are stable and can be identified by high-performance liquid chromatography (HPLC) coupled with electrochemical or ultraviolet detection. To test the hypothesis that hydroxylated salicylates are produced during diaphragm fatigue, we exposed in vitro rat diaphragm strips to a physiological saline solution containing 2.0 mM sodium salicylate for approximately 15 min. The solution was then removed, and the strips were fatigued (20 Hz, 200-ms train duration, 1 train/s) via phrenic nerve stimulation for 30 s-10 min. The diaphragm strips were subsequently homogenized, and the homogenate was analyzed by HPLC coupled with ultraviolet detection. Levels of 2,3-DHB were significantly higher in fatigued than in control nonfatigued strips. There was also a significant correlation between the amount of 2,3-DHB in the fatigued muscle and the accumulated tension-time product developed during fatigue. 2,5-DHB was not consistently identified in control or experimental strips.(ABSTRACT TRUNCATED AT 250 WORDS)

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43

Caraceni, P., A. Gasbarrini, D. H. Van Thiel, and A. B. Borle. "Oxygen free radical formation by rat hepatocytes during postanoxic reoxygenation: scavenging effect of albumin." American Journal of Physiology-Gastrointestinal and Liver Physiology 266, no. 3 (March 1, 1994): G451—G458. http://dx.doi.org/10.1152/ajpgi.1994.266.3.g451.

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Free radical formation and reoxygenation injury were studied in rat hepatocytes perfused with Krebs-Henseleit bicarbonate buffer containing 1% or no albumin. After 2, 2.5, or 3 h of anoxia followed by 1 h reoxygenation in the absence of albumin, free radical formation assessed by low-level chemiluminescence and cell injury measured by lactate dehydrogenase (LDH) release and by trypan blue uptake increased proportionately. Chemiluminescence increased 4- to 7-fold, LDH release and trypan blue uptake increased 1.5- to 2-fold, compared with the end of anoxia. With 1% albumin, there was no increase in free radical formation during reoxygenation, and LDH release returned to control levels. There was a linear relation between the increase in chemiluminescence and the rise in LDH release (r2 = 0.83) and the increase in trypan blue uptake (r2 = 0.80), suggesting that free radical formation during reoxygenation is responsible for the cell injury. These experiments demonstrate that freshly isolated hepatocytes produce oxygen free radicals detectable by low-level chemiluminescence and that reoxygenation injury occurs after a relatively short period of anoxia (2-3 h). Albumin acts as a free radical scavenger, suppresses the release of reactive oxygen species, and significantly reduces reoxygenation injury.

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44

Kondyurin, Alexey V., Pourandokht Naseri, Jennifer M. R. Tilley, Neil J. Nosworthy, Marcela M. M. Bilek, and David R. McKenzie. "Mechanisms for Covalent Immobilization of Horseradish Peroxidase on Ion-Beam-Treated Polyethylene." Scientifica 2012 (2012): 1–28. http://dx.doi.org/10.6064/2012/126170.

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The surface of polyethylene was modified by plasma immersion ion implantation. Structure changes including carbonization and oxidation were observed. High surface energy of the modified polyethylene was attributed to the presence of free radicals on the surface. The surface energy decay with storage time after treatment was explained by a decay of the free radical concentration while the concentration of oxygen-containing groups increased with storage time. Horseradish peroxidase was covalently attached onto the modified surface by the reaction with free radicals. Appropriate blocking agents can block this reaction. All aminoacid residues can take part in the covalent attachment process, providing a universal mechanism of attachment for all proteins. The native conformation of attached protein is retained due to hydrophilic interactions in the interface region. The enzymatic activity of covalently attached protein remained high. The long-term activity of the modified layer to attach protein is explained by stabilisation of unpaired electrons in sp2carbon structures. A high concentration of free radicals can give multiple covalent bonds to the protein molecule and destroy the native conformation and with it the catalytic activity. The universal mechanism of protein attachment to free radicals could be extended to various methods of radiation damage of polymers.

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45

Chappell, Mark A., Lesley F. Miller, and Cynthia L. Price. "Reversible exchange of stable nitroxyl radicals on nanosilver particles." Environmental Chemistry 12, no. 2 (2015): 198. http://dx.doi.org/10.1071/en14093.

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Environmental context Nanometre-sized silver particles promote unique chemical reactions on their surface. This work examines the ability of silver nanoparticles to collect and store unpaired electrons, called radicals, on their surface. This capability by silver nanoparticles could potentially serve to drive degradation reactions in the environment. Abstract Radicals drive important chemical reactions in the environment. These unpaired electron species can be generated by energetic inputs, such as electromagnetic radiation, or from ultrasonication processes, whereby oxygen radicals are generated in aqueous solution through a cavitation mechanism. Previous evidence has demonstrated the potential for radicals to be stored on the surface of metallic gold nanoparticles, thus suggesting a potential transference of radical species from the nanoparticle surface for catalytic reactions, particularly during preparations of nanoparticle suspensions through ultrasonication. This work investigates the potential for the nanosilver (nAg) particles to similarly scavenge radicals from solution. nAg suspensions were reacted with 0.3-mM solutions containing the stable nitroxy radicals 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPONE) and 4-amino-2,2,6,6-tetramethylpiperidino-1-oxyl (TEMPAMINE) analysed by quantitative electron spin resonance (ESR) spectroscopy. In ambient air, the addition of a nAg suspension to the 0.3-mM solutions reduced the integrated ESR intensity of the stable radicals by 50–93% depending on radical species and nAg concentration, which we attributed to the sorption of the radicals onto the nAg surface. In separate experiments, the ESR intensities were further decreased under an Ar atmosphere, suggesting potential competition from ambient OH• to the sorption of the stable radicals. To verify this, we observed substantial increases in the integrated ESR intensity when the systems previously equilibrated under Ar atmosphere were exposed to ambient air. These results demonstrated that nAg scavenged the stable radicals from solution and were exchangeable from the metallic conduction band with OH•. Our work represents the first evidence for this mechanism to be demonstrated for nAg.

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46

Rhoades, R. A., C. S. Packer, D. A. Roepke, N. Jin, and R. A. Meiss. "Reactive oxygen species alter contractile properties of pulmonary arterial smooth muscle." Canadian Journal of Physiology and Pharmacology 68, no. 12 (December 1, 1990): 1581–89. http://dx.doi.org/10.1139/y90-241.

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Reactive oxygen species alter pulmonary arterial vascular tone and cause changes in pulmonary vascular resistance. The objective of this investigation was to determine direct effects of oxygen radicals on the contractile properties of pulmonary arterial smooth muscle. Isolated pulmonary arterial rings from Sprague–Dawley rats were placed in tissue baths containing Earle's balanced salt solution (gassed with 95% O2 – 5% CO2, 37 °C, pH 7.4). Vessels were contracted with 80 mM KCl to establish maximum active force production (PO). All other responses were normalized as percentages of PO for comparative purposes. Reactive oxygen metabolites were generated enzymatically with either the xanthine oxidase (XO) reaction or me glucose oxidase (GO) reaction, or hydrogen peroxide (H2O2) was added directly to the muscle bath. Exposure to XO, GO, or to H2O2 resulted in a contractile response that was sustained during the 30-min exposure period. The muscle fully relaxed following removal of the reactive oxygen species. Resting tension remained unchanged throughout the experimental period, suggesting no functional change in membrane potential. The contractile response was dose dependent and was not prevented by either cyclooxygenase or lipoxygenase inhibition, or by removal of the endothelium. Pretreatment of vessels with superoxide dismutase (SOD) partially blocked the XO-induced contraction, while mannitol or deferoxamine had no effect on the response to XO. However, pretreatment with catalase (CAT) completely blocked the XO-induced contraction. These data suggest that superoxide ions and hydrogen peroxide are the major causative agents. Following O2-radical exposure, vessels showed a decrease in contractile responsiveness to 80 mM KCl (recovery response), suggesting damage to the smooth muscle cells. Administration of SOD or CAT alone significantly improved the recovery response to 80 mM KCl, while SOD plus CAT offered complete protection resulting in final responses to high K+ that were 100% of PO. Vessels precontracted with a submaximal dose of KCl or 5-hydroxytryptamine and then exposed to O2 radicals produced contractile responses that were more than additive, suggesting that "priming" the vessel potentiated reactive oxygen-mediated contraction. These data show that reactive oxygen species can act directly as vasoconstrictors, while simultaneously damaging the arterial smooth muscle such that subsequent contractility is impaired.Key words: oxygen radicals, pulmonary circulation, pulmonary artery, vascular smooth muscle.

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47

Lyons, James R. "Transfer of mass-independent fractionation in ozone to other oxygen-containing radicals in the atmosphere." Geophysical Research Letters 28, no. 17 (September 1, 2001): 3231–34. http://dx.doi.org/10.1029/2000gl012791.

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48

Font-Sanchis, Enrique, Carolina Aliaga, Elena V. Bejan, Raecca Cornejo, and J. C. Scaiano. "Generation and Reactivity toward Oxygen of Carbon-Centered Radicals Containing Indane, Indene, and Fluorenyl Moieties." Journal of Organic Chemistry 68, no. 8 (April 2003): 3199–204. http://dx.doi.org/10.1021/jo026666o.

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49

Zhong, Zhi, Matthias Froh, Mark Lehnert, Robert Schoonhoven, Liu Yang, Henrik Lind, John J. Lemasters, and Ronald G. Thurman. "Polyphenols from Camellia sinenesis attenuate experimental cholestasis-induced liver fibrosis in rats." American Journal of Physiology-Gastrointestinal and Liver Physiology 285, no. 5 (November 2003): G1004—G1013. http://dx.doi.org/10.1152/ajpgi.00008.2003.

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Accumulation of hydrophobic bile acids during cholestasis leads to generation of oxygen free radicals in the liver. Accordingly, this study investigated whether polyphenols from green tea Camellia sinenesis, which are potent free radical scavengers, decrease hepatic injury caused by experimental cholestasis. Rats were fed a standard chow or a diet containing 0.1% polyphenolic extracts from C. sinenesis starting 3 days before bile duct ligation. After bile duct ligation, serum alanine transaminase increased to 760 U/l after 1 day in rats fed a control diet. Focal necrosis and bile duct proliferation were also observed after 1–2 days, and fibrosis developed 2–3 wk after bile duct ligation. Additionally, procollagen-α1(I) mRNA increased 30-fold 3 wk after bile duct ligation, accompanied by increased expression of α-smooth muscle actin and transforming growth factor-β and the accumulation of 4-hydroxynenonal, an end product of lipid peroxidation. Polyphenol feeding blocked or blunted all of these bile duct ligation-dependent changes by 45–73%. Together, the results indicate that cholestasis due to bile duct ligation causes liver injury by mechanisms involving oxidative stress. Polyphenols from C. sinenesis scavenge oxygen radicals and prevent activation of stellate cells, thereby minimizing liver fibrosis.

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50

Scapinello, Marco, Luca Matteo Martini, Paolo Tosi, Andrea Maranzana та Glauco Tonachini. "Molecular growth of PAH-like systems induced by oxygen species: experimental and theoretical study of the reaction of naphthalene with HO (2Π3/2), O (3P), and O2 (3Σ−g)". RSC Advances 5, № 48 (2015): 38581–90. http://dx.doi.org/10.1039/c5ra05129k.

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To assess if reactions with oxygen species can induce a mass increase of polycyclic aromatic hydrocarbons, we exposed naphthalene molecules to an oxidative gas flow containing the radicals H and HO (²Π_3/2) and the diradicals O (³P) and O₂ (³Σ−g).

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