Theoretical and experimental studies of the spin trapping of inorganic radicals by 5,5-dimethyl-1-pyrroline N-oxide (DMPO). 1. carbon dioxide radical anion

Frederick A. Villamena, Edward J. Locigno, A. Rockenbauer, Christopher M. Hadad, Jay L. Zweier

Research output: Contribution to journalArticle

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Abstract

The carbon dioxide radical anion (CO2.-) is known to be generated in vivo through various chemical and biochemical pathways. Electron paramagnetic resonance (EPR) spin trapping with the commonly used spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), has been employed in the detection of CO2.-. The thermodynamics of CO2.- addition to DMPO was predicted using density functional theory (DFT) at the B3LYP/6-31+G**//B3LYP/6-31G* and B3LYP/6-311+G* levels with the polarizable continuum model (PCM) to simulate the effect of the bulk dielectric effect of water on the calculated energetics. Three possible products of CO2 •- addition to DMPO were predicted: (1) a carboxylate adduct, (2) pyrroline-alcohol and (3) DMPO-OH. Experimentally, UV photolysis of H 2O2 in the presence of sodium formate (NaHCO2) and DMPO gave an EPR spectrum characteristic of a C-centered carboxylate adduct and is consistent with the theoretically derived hyperfine coupling constants (hfcc). The pKa of the carboxylate adduct was estimated computationally to be 6.4. The mode of CO2•- addition to DMPO is predicted to be governed predominantly by the spin (density) population on the radical. whereas electrostatic effects are not the dominant factor for the formation of the persistent adduct. The thermodynamic behavior of CO2•- in the aqueous phase is predicted to be similar to that of mercapto radical (.SH), indicating that formation of CO2•- in biological systems may have an important role in the initiation of oxidative damage in cells.

Original languageEnglish
Pages (from-to)13253-13258
Number of pages6
JournalJournal of Physical Chemistry A
Volume110
Issue number49
DOIs
Publication statusPublished - Dec 14 2006

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Carbon Dioxide
Anions
carbon dioxide
trapping
anions
adducts
oxides
carboxylates
formic acid
Paramagnetic resonance
electron paramagnetic resonance
Thermodynamics
thermodynamics
Photolysis
formates
Biological systems
Density functional theory
photolysis
5,5-dimethyl-1-pyrroline-1-oxide
Electrostatics

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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Theoretical and experimental studies of the spin trapping of inorganic radicals by 5,5-dimethyl-1-pyrroline N-oxide (DMPO). 1. carbon dioxide radical anion. / Villamena, Frederick A.; Locigno, Edward J.; Rockenbauer, A.; Hadad, Christopher M.; Zweier, Jay L.

In: Journal of Physical Chemistry A, Vol. 110, No. 49, 14.12.2006, p. 13253-13258.

Research output: Contribution to journalArticle

Villamena, Frederick A. ; Locigno, Edward J. ; Rockenbauer, A. ; Hadad, Christopher M. ; Zweier, Jay L. / Theoretical and experimental studies of the spin trapping of inorganic radicals by 5,5-dimethyl-1-pyrroline N-oxide (DMPO). 1. carbon dioxide radical anion. In: Journal of Physical Chemistry A. 2006 ; Vol. 110, No. 49. pp. 13253-13258.
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abstract = "The carbon dioxide radical anion (CO2.-) is known to be generated in vivo through various chemical and biochemical pathways. Electron paramagnetic resonance (EPR) spin trapping with the commonly used spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), has been employed in the detection of CO2.-. The thermodynamics of CO2.- addition to DMPO was predicted using density functional theory (DFT) at the B3LYP/6-31+G**//B3LYP/6-31G* and B3LYP/6-311+G* levels with the polarizable continuum model (PCM) to simulate the effect of the bulk dielectric effect of water on the calculated energetics. Three possible products of CO2 •- addition to DMPO were predicted: (1) a carboxylate adduct, (2) pyrroline-alcohol and (3) DMPO-OH. Experimentally, UV photolysis of H 2O2 in the presence of sodium formate (NaHCO2) and DMPO gave an EPR spectrum characteristic of a C-centered carboxylate adduct and is consistent with the theoretically derived hyperfine coupling constants (hfcc). The pKa of the carboxylate adduct was estimated computationally to be 6.4. The mode of CO2•- addition to DMPO is predicted to be governed predominantly by the spin (density) population on the radical. whereas electrostatic effects are not the dominant factor for the formation of the persistent adduct. The thermodynamic behavior of CO2•- in the aqueous phase is predicted to be similar to that of mercapto radical (.SH), indicating that formation of CO2•- in biological systems may have an important role in the initiation of oxidative damage in cells.",
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AB - The carbon dioxide radical anion (CO2.-) is known to be generated in vivo through various chemical and biochemical pathways. Electron paramagnetic resonance (EPR) spin trapping with the commonly used spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), has been employed in the detection of CO2.-. The thermodynamics of CO2.- addition to DMPO was predicted using density functional theory (DFT) at the B3LYP/6-31+G**//B3LYP/6-31G* and B3LYP/6-311+G* levels with the polarizable continuum model (PCM) to simulate the effect of the bulk dielectric effect of water on the calculated energetics. Three possible products of CO2 •- addition to DMPO were predicted: (1) a carboxylate adduct, (2) pyrroline-alcohol and (3) DMPO-OH. Experimentally, UV photolysis of H 2O2 in the presence of sodium formate (NaHCO2) and DMPO gave an EPR spectrum characteristic of a C-centered carboxylate adduct and is consistent with the theoretically derived hyperfine coupling constants (hfcc). The pKa of the carboxylate adduct was estimated computationally to be 6.4. The mode of CO2•- addition to DMPO is predicted to be governed predominantly by the spin (density) population on the radical. whereas electrostatic effects are not the dominant factor for the formation of the persistent adduct. The thermodynamic behavior of CO2•- in the aqueous phase is predicted to be similar to that of mercapto radical (.SH), indicating that formation of CO2•- in biological systems may have an important role in the initiation of oxidative damage in cells.

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