ChemInform Abstract: EPR Spin-Trapping Studies of the Reaction of the Hydroxyl Radical with Pyrimidine Nucleobases, Nucleosides and Nucleotides, Polynucleotides, and RNA. Direct Evidence for Sites of Initial Attack and for Strand Breakage.

ChemInform ◽  
2010 ◽  
Vol 25 (6) ◽  
pp. no-no
Author(s):  
H. CATTERALL ◽  
M. J. DAVIES ◽  
B. C. GILBERT ◽  
N. P. POLACK
Keyword(s):  
Hydroxyl Radical ◽  
Direct Evidence ◽  
Spin Trapping ◽  
Initial Attack ◽  
Strand Breakage ◽  
Epr Spin Trapping

Synthesis and EPR Evaluation of the Nitrone PBN-[tert-13C] for Spin Trapping Competition

2002 ◽  
Vol 57 (1) ◽  
pp. 127-132 ◽  
Author(s):  
Yong-Kang Zhang ◽  
Kirk R. Maples
Keyword(s):  
Free Radicals ◽  
Hydroxyl Radical ◽  
Hyperfine Splitting ◽  
Internal Standard ◽  
Spin Trapping ◽  
Epr Spectrum ◽  
Competition Study ◽  
Epr Signal ◽  
Signal Overlap ◽  
Epr Spin Trapping

N-[tert-13C]Butyl C-phenyl nitrone (PBN-[tert-13C]) has been synthesized for an EPR spin trapping competition study. The newly synthesized PBN-[tert-13C] shows different 13C-hyperfine splitting constants (a13C) when it traps free radicals as compared to another 13C-labeled PBN analogue, N-tert-butyl C-phenyl [nitronyl-13C]nitrone (PBN-[nitronyl-13C]). The PBN- [tert-13C] hydroxyl adduct gives a larger a13C value (5.14 G) as compared to the PBN-[nitronyl-13C] hydroxyl adduct (4.36 G). This gain ofthe a13C value decreases the chance of EPR signal overlap, thus providing a more resolved EPR spectrum when PBN-[tert-13C] is used as an internal standard for EPR spin trapping competition studies of hydroxyl radical formation.

Enhancement of hydroxyl radical generation by phenols and their reaction intermediates during ozonation

1998 ◽  
Vol 38 (6) ◽  
pp. 147-154 ◽  
Author(s):  
Hideo Utsumi ◽  
Sang-Kuk Han ◽  
Kazuhiro Ichikawa
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Spin Trapping ◽  
Active Species ◽  
Generation Rate ◽  
Peak Height Ratio ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Phenol Derivatives ◽  
Semiquinone Radicals

Generation of hydroxyl radicals, one of the major active species in ozonation of water was directly observed with a spin-trapping/electron spin resonance (ESR) technique using 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) as a spin-trapping reagent. Hydroxyl radical were trapped with DMPO as a stable radical, DMPO-OH. Eighty μM of ozone produced 1.08 X 10-6M of DMPO-OH, indicating that 1.4% of •OH is trapped with DMPO. Generation rate of DMPO-OH was determined by ESR/stopped-flow measurement. Phenol derivatives increased the amount and generation rate of DMPO-OH, indicating that phenol derivatives enhance •OH generation during ozonation of water. Ozonation of 2,3-, 2,5-, 2,6-dichlorophenol gave an ESR spectra of triplet lines whose peak height ratio were 1:2:1. ESR parameters of the triplet lines agreed with those of the corresponding dichloro-psemiquinone radical. Ozonation of 2,4,5- and 2,4,6-trichlorophenol gave the same spectra as those of 2,5- and 2,6-dichlorophenol, respectively, indicating that a chlorine group in p-position is substituted with a hydroxy group during ozonation. Amounts of the radical increased in an ozone-concentration dependent manner and were inhibited by addition of hydroxyl radical scavengers. These results suggest that p-semiquinone radicals are generated from the chlorophenols by hydroxyl radicals during ozonation. The p-semiquinone radicals were at least partly responsible for enhancements of DMPO-OH generation.

Photoredox Reactions of Iodo Iron(III) Complexes Containing Tetradentate Ligands

2001 ◽  
Vol 66 (1) ◽  
pp. 109-118 ◽  
Author(s):  
Jozef Šima ◽  
Dáša Lauková ◽  
Vlasta Brezová
Keyword(s):  
Schiff Bases ◽  
Spin Trapping ◽  
Molar Ratio ◽  
Oh Radicals ◽  
Solvated Electrons ◽  
Open Chain ◽  
Tetradentate Ligands ◽  
Visible Irradiation ◽  
Epr Spin Trapping ◽  
Spin Trapping Technique

Photoredox reactions occurring in irradiated methanolic solutions of trans-[FeIII(R,R'-salen)(CH3OH)I], where R,R'-salen2- are N,N'-ethylenebis(R,R'-salicylideneiminato), tetradentate open-chain N2O2-Schiff bases with R,R' = H, 5-Cl, 5-Br, 3,5-di-Br, 3,5-di-(CH3), 3-OCH3, 5-OCH3, have been investigated and their mechanism proposed. The complexes are redox-stable in the dark. Ultraviolet and/or visible irradiation of methanolic solution of the complexes induces photoreduction of Fe(III) to Fe(II). Depending on the composition of the irradiated solutions, •CH2OH radicals or solvated electrons were identified by the EPR spin trapping technique. The final product of the photooxidation coupled with the photoreduction of Fe(III) is formaldehyde and the molar ratio of Fe(II) and CH2O is close to 2 : 1. The efficiency of the photoredox process is strongly wavelength-dependent and influenced by the peripheral groups R,R' of the tetradentate ligands.

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