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.

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.

scholarly journals The spin trapping of pyrimidine nucleotide free radicals in a Fenton system

1989 ◽  
Vol 261 (3) ◽  
pp. 831-839 ◽  
Author(s):  
W D Flitter ◽  
R P Mason
Keyword(s):  
Free Radicals ◽  
Hydroxyl Radical ◽  
Spin Trap ◽  
Gamma Ray ◽  
Thiobarbituric Acid ◽  
Spin Trapping ◽  
Pyrimidine Nucleotide ◽  
Gamma Ray Irradiation ◽  
Radical Attack ◽  
Fenton System

The reaction of the hydroxyl radical, generated by a Fenton system, with pyrimidine deoxyribonucleotides was investigated by using the e.s.r. technique of spin trapping. The spin trap t-nitrosobutane was employed to trap secondary radicals formed by the reaction of the hydroxyl radical with these nucleotides. The results presented here show that hydroxyl-radical attack on thymidine, 2-deoxycytidine 5-monophosphate and 2-deoxyuridine 5-monophosphate produced nucleotide-derived free radicals. The results indicate that .OH radical attack occurs predominantly at the carbon-carbon double bond of the pyrimidine base. The e.s.r. studies showed a good correlation with previous results obtained by authors who used x- or gamma-ray irradiation to generate the hydroxyl radical. A thiobarbituric acid assay was also used to monitor the damage produced to the nucleotides by the Fenton system. These results showed qualitative agreement with the spin-trapping studies.

Evaluation of Methanol Induced Free Radicals in Mice Liver

2017 ◽  
Vol 70 (5) ◽  
pp. 499 ◽  
Author(s):  
Lifang Zhou ◽  
Hongli Zhao ◽  
Tieying Pan ◽  
Adrian Trinchi ◽  
Minbo Lan ◽  
...  
Keyword(s):  
Free Radicals ◽  
Harmful Effect ◽  
Spin Trapping ◽  
Enzyme Assays ◽  
Paramagnetic Resonance ◽  
Mice Liver ◽  
Epr Spin Trapping ◽  
Electron Paramagnetic ◽  
Trapping Agent ◽  
Spin Trapping Technique

Methanol induced oxidative stress (OS) models in mice were successfully established and evaluated by the electron paramagnetic resonance (EPR) spin trapping technique. The capacity for removal of reactive oxygen species (ROS) free radicals by rhubarb and vitamin C (Vc) as candidate materials was also investigated. EPR was employed to determine the free radicals generated from a spin trapping agent, α-phenyl-N-tert-butylnitrone (PBN), that reacted with the ROS. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX), and the level of malondialdehyde (MDA) were also evaluated by enzyme assays. The results indicated that methanol clearly promoted the generation of ROS free radicals in the liver of mice. The activity of SOD and GSH-PX was reduced significantly, although the level of MDA was increased as a result of the harmful effect of methanol. In addition, rhubarb and Vc exhibited a protective effect on the mice liver under acute OS.

scholarly journals The oxidation of oxyhaemoglobin by glyceraldehyde and other simple monosaccharides

1984 ◽  
Vol 217 (3) ◽  
pp. 615-622 ◽  
Author(s):  
P J Thornalley ◽  
S P Wolff ◽  
M J C Crabbe ◽  
A Stern
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Phosphate Buffer ◽  
Spin Trap ◽  
Spin Trapping ◽  
Free Radical Production ◽  
Radical Production ◽  
Hydroxyalkyl Radical ◽  
Aldehyde Derivative

Glyceraldehyde and other simple monosaccharides oxidize oxyhaemoglobin to methaemoglobin in phosphate buffer at pH 7.4 and 37 degrees C, with the concomitant production of H2O2 and an alpha-oxo aldehyde derivative of the monosaccharide. Simple monosaccharides also reduce methaemoglobin to ferrohaemichromes (non-intact haemoglobin) at pH 7.4 and 37 degrees C. Carbonmonoxyhaemoglobin is unreactive towards oxidation by autoxidizing glyceraldehyde. Free-radical production from autoxidizing monosaccharides with haemoglobins was observed by the e.s.r. technique of spin trapping with the spin trap 5,5-dimethyl-l-pyrroline N-oxide. Hydroxyl and l-hydroxyalkyl radical production observed from monosaccharide autoxidation was quenched in the presence of oxyhaemoglobin and methaemoglobin. The haemoglobins appear to quench the free radicals by reaction with the free radicals and/or the ene-diol precursor of the free radical.

Spin trapping in photochemistry of coordination compounds

1982 ◽  
Vol 60 (12) ◽  
pp. 1565-1573 ◽  
Author(s):  
Detlef Rehorek ◽  
Horst Hennig
Keyword(s):  
Coordination Compounds ◽  
Spin Trap ◽  
Spin Trapping ◽  
Photochemical Reactions ◽  
Paramagnetic Species ◽  
Side Reactions ◽  
Limited Extent ◽  
Solvated Electrons ◽  
Spin Traps ◽  
Spin Trapping Technique

The application of spin-trapping technique to detect short-lived paramagnetic species formed during photochemical reactions of coordination compounds is reviewed. Interference of radical recombinations by scavenging action of spin traps has been pointed out to be important at high spin-trap concentrations only. Due to only a limited extent of side reactions, nitrosodurene and phenyl N-tert-butyl nitrone were found to be excellent spin traps for the study of photoreactions of metal complexes in nonpolar solutions, whereas 5,5-dimethyl pyrroline-1-oxide is recommended for aqueous solutions. Using these spin traps, both organic and inorganic radicals, e.g. H, Cl, N3, CN, OH, O2−, as well as solvated electrons and metal-centered free radicals have been detected during the photolysis of coordination compounds. The detection of singlet oxygen by reaction with 2,2,6,6-tetramethyl piperidine is briefly discussed.

Free Radicals Generated in Photocatalytic Oxidation of Some Amines and Diamines

1996 ◽  
Vol 1 (2) ◽  
Author(s):  
Ciping Chen ◽  
Daohui Lu ◽  
Guangzhi Xu
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Photocatalytic Oxidation ◽  
Spin Trapping ◽  
Experimental Results ◽  
Epr Spectra ◽  
Radical Species ◽  
Radical Intermediates ◽  
Radical Adduct ◽  
Spin Trapping Technique

AbstractFree radical intermediates produced during photocatalytic oxidation of some typical amines and diamines were investigated by a spin trapping technique. The EPR spectra of N-centered radical adduct and Ccentered radical adduct were observed. Experimental results disclose that these radicals are participants in the initial steps of photodegradation of these compounds. A mechanism which is consistent with the observation of these radical species is discussed.

Ozone exposure generates free radicals in the blood samplesin vitro. Detection by the ESR spin-trapping technique

1998 ◽  
Vol 29 (2) ◽  
pp. 127-135 ◽  
Author(s):  
Ikuko Ueno ◽  
Mikio Hoshino ◽  
Toshiaki Miura ◽  
Nariko Shinriki
Keyword(s):  
Free Radicals ◽  
Spin Trapping ◽  
Ozone Exposure ◽  
Esr Spin Trapping ◽  
Spin Trapping Technique

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.

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