Assignment of the EPR spectrum of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) superoxide spin adduct

Jean Louis Clément, Nicolas Ferré, Didier Siri, Hakim Karoui, A. Rockenbauer, Paul Tordo

Research output: Contribution to journalArticle

55 Citations (Scopus)

Abstract

(Chemical Equation Presented) Spin trapping consists of using a nitrone or a nitroso compound to "trap" an unstable free radical as a long-lived nitroxide that can be characterized by electron paramagnetic resonance (EPR) spectroscopy. The formation of DMPO-OOH, the spin adduct resulting from trapping superoxide (O2•-) with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), has been exploited to detect the generation of superoxide in a wide variety of biological and chemical systems. The 12-line EPR spectrum of DMPO-OOH has been either reported or mentioned in more than a thousand papers. It has been interpreted as resulting from the following couplings: AN ≃ 1.42 mT, AHβ ≃ 1.134 mT, and A (1H) ≃ 0.125 mT. However, the DMPO-OOH EPR spectrum has an asymmetry that cannot be reproduced when the spectrum is calculated considering a single species. Recently, it was proposed that the 0.125 mT splitting was misassigned and actually results from the superimposition of two individual EPR spectra associated with different conformers of DMPO-OOH. We have prepared 5,5-dimethyl-[3,3-2H2]-1-pyrroline N-oxide (DMPO-d2), and we showed that the EPR spectrum of the corresponding superoxide spin adduct is composed of only six lines, in agreement with the assignment of the 0.125 mT splitting to a γ-splitting from a hydrogen atom bonded to carbon 3 of DMPO. This result was supported by DFT calculations including water solvation, and the asymmetry of the DMPO-OOH EPR spectrum was nicely reproduced assuming a chemical exchange between two conformers.

Original languageEnglish
Pages (from-to)1198-1203
Number of pages6
JournalJournal of Organic Chemistry
Volume70
Issue number4
DOIs
Publication statusPublished - Feb 18 2005

Fingerprint

Superoxides
Paramagnetic resonance
Nitroso Compounds
5,5-dimethyl-1-pyrroline-1-oxide
Solvation
Discrete Fourier transforms
Free Radicals
Hydrogen
Carbon
Spectroscopy
Atoms
Oxides
Water

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

Assignment of the EPR spectrum of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) superoxide spin adduct. / Clément, Jean Louis; Ferré, Nicolas; Siri, Didier; Karoui, Hakim; Rockenbauer, A.; Tordo, Paul.

In: Journal of Organic Chemistry, Vol. 70, No. 4, 18.02.2005, p. 1198-1203.

Research output: Contribution to journalArticle

Clément, Jean Louis ; Ferré, Nicolas ; Siri, Didier ; Karoui, Hakim ; Rockenbauer, A. ; Tordo, Paul. / Assignment of the EPR spectrum of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) superoxide spin adduct. In: Journal of Organic Chemistry. 2005 ; Vol. 70, No. 4. pp. 1198-1203.
@article{2e0bf4d371a0402e8bd34c35654e0eff,
title = "Assignment of the EPR spectrum of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) superoxide spin adduct",
abstract = "(Chemical Equation Presented) Spin trapping consists of using a nitrone or a nitroso compound to {"}trap{"} an unstable free radical as a long-lived nitroxide that can be characterized by electron paramagnetic resonance (EPR) spectroscopy. The formation of DMPO-OOH, the spin adduct resulting from trapping superoxide (O2•-) with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), has been exploited to detect the generation of superoxide in a wide variety of biological and chemical systems. The 12-line EPR spectrum of DMPO-OOH has been either reported or mentioned in more than a thousand papers. It has been interpreted as resulting from the following couplings: AN ≃ 1.42 mT, AHβ ≃ 1.134 mT, and A Hγ (1H) ≃ 0.125 mT. However, the DMPO-OOH EPR spectrum has an asymmetry that cannot be reproduced when the spectrum is calculated considering a single species. Recently, it was proposed that the 0.125 mT splitting was misassigned and actually results from the superimposition of two individual EPR spectra associated with different conformers of DMPO-OOH. We have prepared 5,5-dimethyl-[3,3-2H2]-1-pyrroline N-oxide (DMPO-d2), and we showed that the EPR spectrum of the corresponding superoxide spin adduct is composed of only six lines, in agreement with the assignment of the 0.125 mT splitting to a γ-splitting from a hydrogen atom bonded to carbon 3 of DMPO. This result was supported by DFT calculations including water solvation, and the asymmetry of the DMPO-OOH EPR spectrum was nicely reproduced assuming a chemical exchange between two conformers.",
author = "Cl{\'e}ment, {Jean Louis} and Nicolas Ferr{\'e} and Didier Siri and Hakim Karoui and A. Rockenbauer and Paul Tordo",
year = "2005",
month = "2",
day = "18",
doi = "10.1021/jo048518z",
language = "English",
volume = "70",
pages = "1198--1203",
journal = "Journal of Organic Chemistry",
issn = "0022-3263",
publisher = "American Chemical Society",
number = "4",

}

TY - JOUR

T1 - Assignment of the EPR spectrum of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) superoxide spin adduct

AU - Clément, Jean Louis

AU - Ferré, Nicolas

AU - Siri, Didier

AU - Karoui, Hakim

AU - Rockenbauer, A.

AU - Tordo, Paul

PY - 2005/2/18

Y1 - 2005/2/18

N2 - (Chemical Equation Presented) Spin trapping consists of using a nitrone or a nitroso compound to "trap" an unstable free radical as a long-lived nitroxide that can be characterized by electron paramagnetic resonance (EPR) spectroscopy. The formation of DMPO-OOH, the spin adduct resulting from trapping superoxide (O2•-) with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), has been exploited to detect the generation of superoxide in a wide variety of biological and chemical systems. The 12-line EPR spectrum of DMPO-OOH has been either reported or mentioned in more than a thousand papers. It has been interpreted as resulting from the following couplings: AN ≃ 1.42 mT, AHβ ≃ 1.134 mT, and A Hγ (1H) ≃ 0.125 mT. However, the DMPO-OOH EPR spectrum has an asymmetry that cannot be reproduced when the spectrum is calculated considering a single species. Recently, it was proposed that the 0.125 mT splitting was misassigned and actually results from the superimposition of two individual EPR spectra associated with different conformers of DMPO-OOH. We have prepared 5,5-dimethyl-[3,3-2H2]-1-pyrroline N-oxide (DMPO-d2), and we showed that the EPR spectrum of the corresponding superoxide spin adduct is composed of only six lines, in agreement with the assignment of the 0.125 mT splitting to a γ-splitting from a hydrogen atom bonded to carbon 3 of DMPO. This result was supported by DFT calculations including water solvation, and the asymmetry of the DMPO-OOH EPR spectrum was nicely reproduced assuming a chemical exchange between two conformers.

AB - (Chemical Equation Presented) Spin trapping consists of using a nitrone or a nitroso compound to "trap" an unstable free radical as a long-lived nitroxide that can be characterized by electron paramagnetic resonance (EPR) spectroscopy. The formation of DMPO-OOH, the spin adduct resulting from trapping superoxide (O2•-) with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), has been exploited to detect the generation of superoxide in a wide variety of biological and chemical systems. The 12-line EPR spectrum of DMPO-OOH has been either reported or mentioned in more than a thousand papers. It has been interpreted as resulting from the following couplings: AN ≃ 1.42 mT, AHβ ≃ 1.134 mT, and A Hγ (1H) ≃ 0.125 mT. However, the DMPO-OOH EPR spectrum has an asymmetry that cannot be reproduced when the spectrum is calculated considering a single species. Recently, it was proposed that the 0.125 mT splitting was misassigned and actually results from the superimposition of two individual EPR spectra associated with different conformers of DMPO-OOH. We have prepared 5,5-dimethyl-[3,3-2H2]-1-pyrroline N-oxide (DMPO-d2), and we showed that the EPR spectrum of the corresponding superoxide spin adduct is composed of only six lines, in agreement with the assignment of the 0.125 mT splitting to a γ-splitting from a hydrogen atom bonded to carbon 3 of DMPO. This result was supported by DFT calculations including water solvation, and the asymmetry of the DMPO-OOH EPR spectrum was nicely reproduced assuming a chemical exchange between two conformers.

UR - http://www.scopus.com/inward/record.url?scp=13844320110&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=13844320110&partnerID=8YFLogxK

U2 - 10.1021/jo048518z

DO - 10.1021/jo048518z

M3 - Article

C2 - 15704951

AN - SCOPUS:13844320110

VL - 70

SP - 1198

EP - 1203

JO - Journal of Organic Chemistry

JF - Journal of Organic Chemistry

SN - 0022-3263

IS - 4

ER -