Formation and EPR spectra of radical species derived from the oxidation of the spin trap, α-phenyl-N-tert-butylnitrone (PBN), and some of its derivatives in 1,1,1,3,3,3-hexafluoropropan-2-ol. Formation of isoxazolidine radical cations

1997 ◽  
pp. 195-202 ◽  
Author(s):  
Lennart Eberson ◽  
Michael P. Hartshorn ◽  
Ola Persson
Keyword(s):  
Spin Trap ◽  
Radical Cations ◽  
Epr Spectra ◽  
Radical Species

EPR spectra and structure of the radical cations of fluorinated benzenes

1997 ◽  
pp. 1625-1632 ◽  
Author(s):  
Akinori Hasegawa ◽  
Yoshiteru Itagaki ◽  
Masaru Shiotani
Keyword(s):  
Radical Cations ◽  
Epr Spectra

scholarly journals The role of the liver in the production of free radicals during halothane anaesthesia in the rat. Quantification of N-tert-butyl-alpha-(4-nitrophenyl)nitrone (PBN)-trapped adducts in bile from halothane as compared with carbon tetrachloride

1991 ◽  
Vol 277 (3) ◽  
pp. 795-800 ◽  
Author(s):  
H M Hughes ◽  
I M George ◽  
J C Evans ◽  
C C Rowlands ◽  
G M Powell ◽  
...  
Keyword(s):  
Free Radicals ◽  
Spin Trap ◽  
Halothane Anaesthesia ◽  
Perfused Liver ◽  
Radical Species ◽  
Tert Butyl ◽  
Biliary Elimination ◽  
Ccl4 Administration ◽  
Liver Preparation

Halothane or CCl4 was co-administered with the spin trap N-tert-butyl-alpha-(4-nitrophenyl)nitrone (PBN) to rats fitted with bile duct cannuli or to isolated perfused liver preparations. Rats maintained under halothane anaesthesia generated significant amounts of free radicals, and 5-9 nmol was excreted in bile over 1 h. No adducts were detected in urine or plasma. The hepatic origin of these free radicals was confirmed by studies on isolated perfused livers where the addition of halothane to the perfusate resulted in the biliary elimination of the same PBN-trapped radical adducts. Similarly, following CCl4 administration, the same radical species were eliminated in bile in the whole animal and the perfused liver preparation. In the perfused liver, over 3 h the total biliary elimination of radicals derived from halothane or CCl4 (administered at equimolar concentrations) was approximately the same (5-7 nmol); however, the elimination of halothane-derived radicals was more rapid over the first 1 h.

scholarly journals Mechanism in the reaction of cytochrome c oxidase with organic hydroperoxides: an ESR spin-trapping investigation

2002 ◽  
Vol 365 (2) ◽  
pp. 461-469 ◽  
Author(s):  
Yeong-Renn CHEN ◽  
Ronald P. MASON
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Spin Trap ◽  
Spin Trapping ◽  
Initial Reaction ◽  
Radical Species ◽  
Alkoxyl Radical ◽  
Tyrosine Residues ◽  
Esr Spin Trapping ◽  
Organic Hydroperoxides

Organic hydroperoxides are of great utility in probing the reaction mechanism and the toxicological consequences of lipid peroxidation. In the present study, ESR spin-trapping was employed to investigate the peroxidation of mitochondrial cytochrome c oxidase (CcO) with t-butyl hydroperoxide (t-BuOOH) and cumene hydroperoxide (CumOOH). The spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was used to detect the radical species formed from the reaction of CcO with t-BuOOH. The presence of t-BuOOH-derived alkoxyl radical (t-BuO˙) as the primary radical indicates reductive scission of the O—O bond by CcO. The ESR signal of DMPO/˙Ot-Bu can be partially abolished by cyanide, implying that the reductive cleavage involved the haem a3CuB binuclear site of CcO. A nitroso spin trap, 2-methyl-2-nitrosopropane (MNP), was used to detect and identify radical species from the reaction of CcO with CumOOH. In addition to the t-BuOOH-derived methyl, hydroxylmethyl and tertiary carbon-centred radicals, a protein-derived radical was detected. The intensity of the ESR signal from the protein radical increased with the CumOOH concentration at low CumOOH/CcO ratios, with maximal intensity at a ratio of 100mol of CumOOH/mol of CcO. The immobilized protein radical adduct of MNP was stable and persistent after dialysis; it was also resistant to proteolytic digestion, suggesting that it was formed in the transmembrane region, a region that is not accessible to proteases. Its signal was greatly enhanced when CcO cysteine residues were chemically modified by N-ethylmaleimide, when the tryptophan residues in CcO were oxidized by N-bromosuccimide, and when tyrosine residues on the surface of CcO were iodinated, showing that a radical equilibrium was established among the cysteine, tryptophan and tyrosine residues of the protein-centred radical. Pre-treatment of CcO with cyanide prevented detectable MNP adduct formation, confirming that the haem a3-CuB binuclear centre was the initial reaction site. When the CcO was pre-treated with 10mM (100 equivalents) of CumOOH, the enzyme activity decreased by more than 20%. This inhibition was persistent after dialysis, suggesting that the detected protein-centred radical was, in part, involved in the irreversible inactivation by CumOOH. Visible spectroscopic analysis revealed that the haem a of CcO was not affected during the reaction. However, the addition of pyridine to the reaction mixture under alkaline conditions resulted in the destruction of the haem centre of CcO, suggesting that its protein matrix rather than its haem a is the target of oxidative damage by the organic hydroperoxide.

scholarly journals Spin-trapping studies on the free-radical products formed by metabolic activation of carbon tetrachloride in rat liver microsomal fractions isolated hepatocytes and in vivo in the rat

1982 ◽  
Vol 204 (2) ◽  
pp. 593-603 ◽  
Author(s):  
E Albano ◽  
K A K Lott ◽  
T F Slater ◽  
A Stier ◽  
M C R Symons ◽  
...  
Keyword(s):  
Free Radical ◽  
Carbon Tetrachloride ◽  
Spin Trap ◽  
Peroxy Radical ◽  
Metabolic Activation ◽  
Spin Trapping ◽  
Metabolic Inhibitors ◽  
Radical Species ◽  
Free Radical Species ◽  
Trichloromethyl Radical

1. The metabolic activation of carbon tetrachloride to free-radical intermediates is an important step in the sequence of disturbances leading to the acute liver injury produced by this toxic agent. Electron-spin-resonance (e.s.r.) spin-trapping techniques were used to characterize the free-radical species involved. 2. Spin trapping was applied to the activation of carbon tetrachloride by liver microsomal fractions in the presence of NADPH, and by isolated intact rat hepatocytes. The results obtained with the spin trap N-benzylidene-2-methylpropylamine N-oxide (‘phenyl t-butyl nitrone’) (PBN) and [13C]carbon tetrachloride provide unequivocal evidence for the formation and trapping of the trichloromethyl free radical in these systems. 3. With the spin trap 2-methyl-2-nitrosopropane, however, the major free-radical species trapped are unsaturated lipid radicals produced by the initiating reaction of lipid peroxidation. 4. Although pulse radiolysis and other evidence support the very rapid formation of the trichloromethyl peroxy radical from the trichloromethyl radical and oxygen, no clear evidence for the trapping of the peroxy radical was obtainable. 5. The effects of a number of free-radical scavengers and metabolic inhibitors on the formation of the PBN-trichloromethyl radical adduct were studied, as were the influences of changing the concentration of PBN and incubation time. 6. High concentrations of the spin traps used were found to have significant effects on cytochrome P-450-mediated reactions; this requires caution in interpreting results of experiments done in the presence of PBN at concentrations greater than 50 mM.

EPR Spectra and Structure of the Radical Cations of Fluorinated Ethylenes and Propenes

1998 ◽  
Vol 71 (11) ◽  
pp. 2547-2554 ◽  
Author(s):  
Yoshiteru Itagaki ◽  
Masaru Shiotani ◽  
Akinori Hasegawa ◽  
Hisao Kawazoe
Keyword(s):  
Radical Cations ◽  
Epr Spectra

ChemInform Abstract: EPR Spectra of the Radical Cations of Some Benzocyclobutenes, Benzocyclopentenes and Benzocyclohexenes.

ChemInform ◽  
2010 ◽  
Vol 24 (22) ◽  
pp. no-no
Author(s):  
D. V. AVILA ◽  
A. G. DAVIES ◽  
E. R. LI ◽  
K. M. NG
Keyword(s):  
Radical Cations ◽  
Epr Spectra

EPR spectra for a range of pyrimidine and s-triazine radical cations

1992 ◽  
pp. 1403 ◽  
Author(s):  
Aidan O'Connell ◽  
Ian D. Podmore ◽  
Martyn C. R. Symons ◽  
Jane L. Wyatt ◽  
Franz A. Neugebauer
Keyword(s):  
Radical Cations ◽  
Epr Spectra
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