scholarly journals Mechanism of tiron as scavenger of superoxide ions and free electrons

2008 ◽  
Vol 22 (6) ◽  
pp. 491-498 ◽  
Author(s):  
Fatai A. Taiwo
Keyword(s):  
Spin Trap ◽  
Cell Entry ◽  
Transfer Reactions ◽  
Spin Adduct ◽  
Semiquinone Radical ◽  
Free Electrons ◽  
Hypoxic Conditions ◽  
Electron Scavenger ◽  
Electron Release ◽  
Molecular Spin

Sodium 4,5-dihydroxybenzene-1,3-disulfonate (tiron) has been reported to be an efficient chelator of certain metal ions, and a substrate in several enzyme reactions. Its small size facilitates cell entry and therefore modulates intracellular electron transfer reactions as an antioxidant by scavenging free radicals. Its reduction by electrochemical and enzymatic methods gives identical products; a semiquinone detectable by EPR spectroscopy. In a test of its use as a spin trap, in comparison with DMPO, tiron does not form a molecular spin-adduct but proves more functional as an electron trap. Electron addition to tiron is more facile than reduction of dioxygen as observed by the non-formation of DMPO-OOH spin-adduct in the system XO/HPX/O2/DMPO/tiron. Rather, it is the tiron semiquinone radical which is formed quantitatively with increasing concentration of hypoxanthine independent of oxygen concentration. These results offer explanation for the action of tiron and its suitability for measuring electron release in hypoxic conditions, and also for mitigating redox-induced toxicity in drug regimes by acting as an electron scavenger.

scholarly journals Estimation of the Postmortem Duration of Mouse Tissue by Electron Spin Resonance Spectroscopy

2011 ◽  
Vol 2011 ◽  
pp. 1-11
Author(s):  
Shinobu Ito ◽  
Tomohisa Mori ◽  
Hideko Kanazawa ◽  
Toshiko Sawaguchi
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Spin Trap ◽  
Detection Sensitivity ◽  
Mouse Tissue ◽  
Spin Adduct ◽  
Simple Method ◽  
Oxidation Stress ◽  
Spin Resonance

Electron spin resonance (ESR) method is a simple method for detecting various free radicals simultaneously and directly. However, ESR spin trap method is unsuited to analyze weak ESR signals in organs because of water-induced dielectric loss (WIDL). To minimize WIDL occurring in biotissues and to improve detection sensitivity to free radicals in tissues, ESR cuvette was modified and used with 5,5-dimethtyl-1-pyrroline N-oxide (DMPO). The tissue samples were mouse brain, hart, lung, liver, kidney, pancreas, muscle, skin, and whole blood, where various ESR spin adduct signals including DMPO-ascorbyl radical (AsA∗), DMPO-superoxide anion radical (OOH), and DMPO-hydrogen radical (H) signal were detected. Postmortem changes in DMPO-AsA∗and DMPO-OOH were observed in various tissues of mouse. The signal peak of spin adduct was monitored until the 205th day postmortem. DMPO-AsA∗in liver (y=113.8–40.7 log (day),R1=-0.779,R2=0.6,P<.001) was found to linearly decrease with the logarithm of postmortem duration days. Therefore, DMPO-AsA∗signal may be suitable for detecting an oxidation stress tracer from tissue in comparison with other spin adduct signal on ESR spin trap method.

Utilisation des pièges à radicaux en vue de mettre en évidence des intermédiaires dans la photolyse de complexes contenant une liaison CoIII—C

1982 ◽  
Vol 60 (12) ◽  
pp. 1402-1413 ◽  
Author(s):  
Philippe Maillard ◽  
Charles Giannotti
Keyword(s):  
Free Radicals ◽  
Hydrogen Atom ◽  
Spin Trap ◽  
Spin Trapping ◽  
Spin Adduct ◽  
Efficient Manner ◽  
Solvent Cage ◽  
Selective Deuteration ◽  
Equatorial Ligand ◽  
Spin Trapping Technique

Using the spin trapping technique with 5,5′-dimethyl 1-pyrroline N-oxide (DMPO), phenyl-N-tert-butyl nitrone (PBN), nitrosodurene (ND), and α-4-pyridyl 1-oxide N-tert-butl nitrone (4-POBN), or their mixtures, we have been able to detect two types of radicals, one is a hydrogen atom spin adduct and the other is the corresponding alkyl of the alkylcobaloximes, salens or cobalamines.By the use of selective deuteration and the preparation of the benzyl bis(diphenylglyoximato)-pyridinato cobaloxime, we have shown that the spin trapped hydrogen atom comes from the chelated hydrogen of the dimethylglyoximato anion of the equatorial ligand of CoIII complexes. Using a mixture of two spin traps gives rise to an esr spectrum containing, at the same time, the hydrogen atom and alkyl spin adducts.To explain such an efficient spin trapping reaction while the homolysis is in competition with a β-elimination process, it should be postulated that the photolysis of such compounds proceeds through a solvent cage environment. This hypothesis explains the strong influence of solvents on the nature of the free radicals trapped. Also the spin trap diffuses in the solvent cage, and is able to trap in a very efficient manner any free radicals occurring in the solvent cage. The excited CoIII complexes and the spin trap in the solvent cage behave like an exciplex, which could explain the spin trapping of the hydrogen atom.

Homolytic Scission of Interunitary Bonds in Lignin Induced by Ultrasonic Irradiation of MWL Dissolved in Dimethylsulfoxide

Holzforschung ◽  
2000 ◽  
Vol 54 (4) ◽  
pp. 357-364 ◽  
Author(s):  
Aki Yoshioka ◽  
Teruyuki Seino ◽  
Masayoshi Tabata ◽  
Mitsuo Takai
Keyword(s):  
Ultrasonic Irradiation ◽  
Spin Trap ◽  
Spin Trapping ◽  
Spin Adduct ◽  
Dmso Solution ◽  
Picea Jezoensis ◽  
Spin Resonance ◽  
Spin Trapping Technique ◽  
Secondary Carbon ◽  
Stable Nitroxide

SummaryAn electron spin resonance (ESR) method combined with a spin trapping technique was applied to trap and characterize unstable radicals which were generated by ultrasonic irradiation of the dimethylsulfoxide (DMSO) solution of a softwood, Yezo Spruce (Picea jezoensiscarr.) lignin. It was found that an unstable secondary carbon radical, ~CH • in the solution was trapped as the stable nitroxide spin adduct when the DMSO solution was subjected to ultrasonic irradiation in the presence of a spin trapping reagent: 2,4,6-tri-tert-butylnitrosobenzene (BNB) at 50°C for 30 min. This means that the alkyl phenyl ether bonds, ~CH-O-phenyl, known as interunitary bonds in lignins were homolytically cleaved by the ultrasonic irradiation, although the phenoxy radical Ph-O •, called guaiacoxy radical, i.e. the counter radical of the secondary carbon radical, was not trapped by the BNB spin trap. This suggests that the trapping of the guaiacoxy radical, having a methoxy group in anortho-position, by the BNB molecule, carrying two bulky butyl groups in theortho-positions, is sterically hindered.

Free radical production during phenylhydrazine-induced hemolysis

1982 ◽  
Vol 60 (12) ◽  
pp. 1528-1531 ◽  
Author(s):  
H. A. O. Hill ◽  
P. J. Thornalley
Keyword(s):  
Spin Trap ◽  
Spin Adduct ◽  
Phenyl Radical ◽  
Erythrocyte Suspension ◽  
Phenyl Radicals ◽  
Spin Traps ◽  
Free Radical Production ◽  
Radical Trapping ◽  
Radical Production ◽  
Moderate Yield

The production of phenyl radicals during phenylhydrazine-induced hemolysis has been demonstrated by the use of the spin traps, DMPO, M4PO, and LINPyBN. The phenyl spin adducts of DMPO and M4PO were produced in moderate yield by an oxygenated 1% erythrocyte suspension. With the lipid soluble spin trap LINPyBN, a dramatic increase (400%) in the yield of phenyl spin adduct was observed despite little increase in the rate of phenyl radical trapping. The production of phenyl spin adducts was decreased when phenylhydrazine-4-sulphonic acid or carbonmonoxyhemoglobin-containing erythrocytes were used. These results suggest that the reaction of phenylhydrazine with oxyhemoglobin leads to the formation of phenyl radicals that are preferentially trapped in the erythrocyte membrane.

An Electron Spin Resonance Study of the Spin Adducts of OH and HO2 Radicals with Nitrones in the Ultraviolet Photolysis of Aqueous Hydrogen Peroxide Solutions

1974 ◽  
Vol 52 (20) ◽  
pp. 3549-3553 ◽  
Author(s):  
John R. Harbour ◽  
Vivian Chow ◽  
James R. Bolton
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Spin Trap ◽  
Spin Adduct ◽  
Electron Spin Resonance Study ◽  
Aqueous Hydrogen Peroxide ◽  
Low Concentrations ◽  
Radical Adduct ◽  
Spin Resonance ◽  
High Concentrations

The photolysis of H2O2 in aqueous solution has been used to study and characterize electron spin resonance (e.s.r.) spectra of the •OH and •HO2 radical spin adducts with the spin traps 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and phenyl-t-butyl nitrone (PBN). At high concentrations of spin trap and low concentrations of H2O2 an e.s.r. spectrum is obtained which we assign to the •OH radical adduct (for DMPO, aN = 15.3 G, aβH = 15.3 G, [Formula: see text] and g = 2.0060; for PBN, aN = 15.3 G, aβH = 2.75 G, and g = 2.0057). At low concentrations of spin trap and high concentrations of H2O2• a second spin adduct spectrum is obtained which we assign to the spin adduct of the HO2 radical (for DMPO, aN = 14.3 G, aβH = 11.7 G, aγH = 1.25 G, g = 2.0061; for PBN, aN = 14.8 G, aβH = 2.75 G, and g = 2.0057).

scholarly journals An Investigation of the Molecules O2, CHCl3, c—C4F8, C7F14 and HBr by Electron Cyclotron Resonance (ECR) Technique at Energies ≤ 0.4 eV

1974 ◽  
Vol 29 (3) ◽  
pp. 389-399
Author(s):  
A. A. Christodoulides ◽  
E. Schultes ◽  
R. Schumacher ◽  
R. N. Schindler
Keyword(s):  
Cyclotron Resonance ◽  
Electron Cyclotron Resonance ◽  
Electron Attachment ◽  
Energy Scale ◽  
Good Choice ◽  
Electron Cyclotron ◽  
Free Electrons ◽  
Carrier Gas ◽  
Electron Scavenger ◽  
Helium Gas

Preliminary experiments have shown that helium gas can be considered a good choice to be used in electron cyclotron resonance (ECR) studies, at the same time as a carrier gas and as a source of production of free electrons. An account of destruction of He metastable atoms present in the flowstream is given. Changes in the linewidth with or without the electron scavenger and thermalization of the electrons are discussed. The energy dependence for the electron attachment to the molecules O2, CHCl3, c-C4F8, C7F14, and HBr is investigated. The energy scale for electron attachment processes in relation to the input microwave power is established for He carrier gas. Such processes can be studied by employing the ECR technique from thermal energies up to 0.4 eV

scholarly journals Synthesis and Plane Selective Spin Trapping of a Novel Trap 5,5-Dimethyl-3-(2-ethoxycarbonylethyl)-1-pyrroline N-oxide

1990 ◽  
Vol 45 (7) ◽  
pp. 1075-1083 ◽  
Author(s):  
Yong-Kang Zhang ◽  
Dao-Hui Lu ◽  
Guang-Zhi Xu
Keyword(s):  
Free Radicals ◽  
Spin Trap ◽  
Life Time ◽  
Geometric Isomer ◽  
Radical Addition ◽  
Spin Adduct ◽  
Conformation Analysis ◽  
Epr Spectrum ◽  
Butoxy Radical ◽  
Configuration And Conformation

A novel cyclic nitrone spin trap 5,5-dimethyl-3-(2-ethoxycarbonylethyl)-1-pyrroline N-oxide has been prepared and its ability to trap a series of transient free radicals has been investigated. This nitrone scavenges free radicals to give persistent nitroxides, e.g., the half life-times of hydroxyl radical adducts and tert-butoxy radical adducts in benzene &gt;30 min, and the life-time of acetyl adducts &gt;60 min. The EPR spectrum of 2,2-dimethyl-4-(3-hydroxypropyl)pyrrolidinyl-1-oxyl aminoxyl shows that the hyperfine splitting constants of twoβ-hydrogens are equal to 14.58 G and 23.29 G respectively, i.e., the two β-hydrogens are not magnetically equivalent. Radical addition to the nitrone is probably plane selective affording only one of the two possible geometric isomer pairs of the spin adduct nitroxides. The trans approach mechanism is proposed through configuration and conformation analysis.

Ultrafast capture of free electrons in optically ionized gases by the electron scavenger SF6

2006 ◽  
Vol 429 (4-6) ◽  
pp. 350-354 ◽  
Author(s):  
Tobias Kampfrath ◽  
Luca Perfetti ◽  
Dirk O. Gericke ◽  
Christian Frischkorn ◽  
Petra Tegeder ◽  
...  
Keyword(s):  
Free Electrons ◽  
Electron Scavenger

Dynamic studies of silicide-mediated crystallization of amorphous silicon

1992 ◽  
Vol 50 (2) ◽  
pp. 1352-1353
Author(s):  
C. Hayzelden ◽  
J. L. Batstone
Keyword(s):  
Ion Implantation ◽  
Solid Phase ◽  
Metallic Phase ◽  
Single Crystal Substrate ◽  
Free Electrons ◽  
Melt Temperature ◽  
Transmission Electron ◽  
Crystal Substrate ◽  
High Resolution Tem

Epitaxial reordering of amorphous Si(a-Si) on an underlying single-crystal substrate occurs well below the melt temperature by the process of solid phase epitaxial growth (SPEG). Growth of crystalline Si(c-Si) is known to be enhanced by the presence of small amounts of a metallic phase, presumably due to an interaction of the free electrons of the metal with the covalent Si bonds near the growing interface. Ion implantation of Ni was shown to lower the crystallization temperature of an a-Si thin film by approximately 200°C. Using in situ transmission electron microscopy (TEM), precipitates of NiSi2 formed within the a-Si film during annealing, were observed to migrate, leaving a trail of epitaxial c-Si. High resolution TEM revealed an epitaxial NiSi2/Si(l11) interface which was Type A. We discuss here the enhanced nucleation of c-Si and subsequent silicide-mediated SPEG of Ni-implanted a-Si.Thin films of a-Si, 950 Å thick, were deposited onto Si(100) wafers capped with 1000Å of a-SiO2. Ion implantation produced sharply peaked Ni concentrations of 4×l020 and 2×l021 ions cm−3, in the center of the films.

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