Spin trapping for hydroxyl in water: a kinetic evaluation of two popular traps

Marriott, P. R.; Perkins, M. J.; Griller, D.

doi:10.1139/v80-125

Cited by 110 publications

(54 citation statements)

References 7 publications

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“…6 were calculated with k DMPO ＝2.0×10 9 M "1 s "1 . This value is identical to that measured by spin trapping, 22) although a diŠerent method was applied. Therefore, it is conclusive that DMPO acted as an OH scavenger.…”

Section: Measurement Of the Consumption Of Dissolved Oxygensupporting

confidence: 73%

Kinetic Analysis of the Effect of (−)-Epigallocatechin Gallate on the DNA Scission Induced by Fe(II)

Ohashi

Yoshinaga

Yoshioka

2002

Bioscience, Biotechnology, and Biochemistry

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Section: Measurement Of the Consumption Of Dissolved Oxygensupporting

confidence: 73%

Kinetic Analysis of the Effect of (−)-Epigallocatechin Gallate on the DNA Scission Induced by Fe(II)

Ohashi

Yoshinaga

Yoshioka

2002

Bioscience, Biotechnology, and Biochemistry

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“…3). The half-lives of DMPO-OH 5 or DMPO-OOH 6,7 at basic pH are much shorter than those at neutral or acidic conditions, and the decrease of the intensity of DMPO-OH signal can be considered as the unstability of these radical species. The optimum pH was found to be around pH 8.5, thus, the catalytic action of H + may not be plausible.…”

Section: Resultsmentioning

confidence: 99%

DMPO-OH Radical Formation from 5,5-Dimethyl-1-pyrroline N-Oxide (DMPO) in Hot Water

Shoji

Abe

et al. 2007

ANAL. SCI.

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The spin-trapping method with 5,5-dimethyl-1-pyrroline Noxide (DMPO) has been widely accepted as an assay method to measure hydroxyl radical formation, and to detect the hydroxyl radical scavenging activity of a compound. Although unstability of DMPO is claimed because it turns yellow with time even at -20˚C in a sealed tube under vacuum, 1 the basic chemistry of DMPO and DMPO-OH has not been well understood.In a previous work, 2 we noticed very weak DMPO-OH signals in the baseline of a negative control spectrum which was obtained after standing DMPO solution at 37˚C for 24 h. We suspected that in a DMPO aqueous solution at a higher concentration and at a higher temperature, an appropriate amount of DMPO-OH might generate. And we considered that this reaction should provide a practical preparation method to obtain DMPO-OH radical as a simple aqueous solution which contains no other materials except unreacted DMPO. Also this DMPO-OH aqueous solution may be utilized in the investigation of the chemical or physicochemical properties of DMPO-OH radicals.When DMPO was dissolved in purified water and the solution was heated at 70˚C for 30 min, a sufficient amount of DMPO-OH radical formation was observed by ESR ( Fig. 1). Under an argon atmosphere, DMPO-OH formation was minimized to 1/4, and this slightly increased under a dioxygen atmosphere. This indicates that dioxygen participates in the reaction. Previously, Makino et al. observed DMPO-OH formation in an aqueous mixture of DMPO and 1 mM FeCl3. Based on this observation of the formation of iron chelate with DMPO at 77 K, and DMPO-OCH3 formation in the presence of CH3OH, researchers elucidated that nucleophilic attachment of water to DMPO should occur in the presence of Fe 3+ ion. 3 To study the effect of a small number of metal ions in purified water, we replaced the purified water with ultra-pure water for ICP-MS measurements; the latter should contain iron of no more than 1 ppb. In ultrapure water, and under an argon atmosphere, DMPO-OH signal was still observed after heating, although its intensity decreased to about 1/20. In this communication, we describe DMPO-OH radical formation in hot water, in which dissolved dioxygen participates in the reaction and metal ions such as Fe 3+ might catalyze DMPO-OH formation. University, Japan *3 Tokyo Metropolitan Industrial Technology Research Institute, Itabashi, Japan *4 Faculty of Pharmaceutical Sciences, Nagoya City University, Mizuho, Japan When an aqueous solution of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was heated at 70˚C for 30 min, formation of DMPO-OH was observed by ESR. This DMPO-OH radical formation was suppressed under an argon atmosphere. When water was replaced with ultra-pure water for ICP-MS experiments, DMPO-OH radical formation was also diminished. Under an argon atmosphere in ultra-pure water, the intensity of the DMPO-OH signal decreased to about 1/20 of that observed under aerobic conditions with regular purified water. The addition of hydroxyl radical scavengers such as mannitol did not a...

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“…However, the rate constant of trapping OH-by DMPO, 2.1-5.7 x 109 M-1'sec-1 (16,21,22), is also much greater than those of O2-(10 M-1 sec'-), and HOO-(6.6 x 103 M-1 sec-1) (22). In view of these data, the major product of the reaction is°27/HO2', at least 105-fold more concentrated than OH-radical.…”

Section: Resultsmentioning

confidence: 99%

Manganese(II)-bicarbonate-mediated catalytic activity for hydrogen peroxide dismutation and amino acid oxidation: detection of free radical intermediates.

Yim

Berlett

Chock

et al. 1990

Proc. Natl. Acad. Sci. U.S.A.

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To examine the structural identities of reactive free radicals and the mechanism of the oxidative modification of proteins, we used EPR and spin-trapping methods to investigate the oxidation of amino acids by H202 as well as the decomposition of H202 itself catalyzed by Mn(11) ions. Superoxide and hydroxyl radicals (02T and OH-) were trapped by a spin trap, 5,5-dimethyl-1-pyrroline-1-oxide (DMPO), in a reaction mixture containing Mn(11) and H202 in bicarbonate/ CO2 buffer. When Hepes was used in place of bicarbonate buffer, superoxide radical was not observed, indicating the importance of bicarbonate buffer. With addition of L-leucine to a similar reaction mixture, a leucine-derived radical that replaced the DMPO-superoxide adduct was detected in the absence and presence of DMPO. Using various isotope-enriched L-leucines, we successfully identified this radical as a hydronitroxide, -OOC(R)CHNHO-. The data are consistent with the formation of a transient "caged" OHS in the inner coordination sphere of Mn(iI). This caged OHS is likely to undergo an intramolecular hydrogen-atom abstraction from the Mn-bound H202 or amino acid. Two reaction schemes are proposed to account for the experimental results shown here and in the preceding papers.Mn ions are known to participate in certain superoxide dismutases (1, 2) and catalases (3,4). Low molecular weight complexes of Mn have also been observed to protect cells from oxygen damage (5, 6). This capability has been attributed to the fact that Mn(II) when complexed with certain anionic ligands is capable of catalyzing the dismutation of superoxide anion, 02 . Catalase-like activity has also been observed for nonprotein Mn(II) complexes (7,8). In addition, transition metal ions such as Fe and Cu are known to catalyze oxygen radical-mediated oxidative modification of proteins, a process implicated in protein turnover, aging, and oxygen toxicity (9, 10).In the preceding papers (8, 11), we showed that Mn(II)-bicarbonate complexes are capable of catalyzing the disproportionation of H202 to form 02 and the oxidation of amino acid by H202 to form the carbonyl derivatives of the amino acid, NH4', and CO2. To investigate the mechanisms ofthese catalytic reactions, we have used an EPR spectrometer together with a spin trap to detect short-lived free radical intermediates for these reactions. Various isotope-enriched leucines were also used for identifying the leucine-derived radical. Based on the results of this study and the kinetic and product analyses presented in the preceding papers (8, 11), two mechanisms are proposed, one for the catalase-like activity and the other for the oxidation of amino acids. MATERIALS AND METHODSThe spin trap 5,5-dimethyl-1-pyrroline-1-oxide (DMPO), purchased from Aldrich, was further purified with activated charcoal under N2 gas in the dark (12) EPR spectra were recorded at 100-kHz frequency modulation and 9.87-GHz microwave irradiation with a Bruker ESP 300 spectrometer operated in the TM110 mode. An aqueous flat cell (-150 Al) was used and t...

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Spin trapping for hydroxyl in water: a kinetic evaluation of two popular traps

Cited by 110 publications

References 7 publications

Kinetic Analysis of the Effect of (−)-Epigallocatechin Gallate on the DNA Scission Induced by Fe(II)

Kinetic Analysis of the Effect of (−)-Epigallocatechin Gallate on the DNA Scission Induced by Fe(II)

DMPO-OH Radical Formation from 5,5-Dimethyl-1-pyrroline N-Oxide (DMPO) in Hot Water

Manganese(II)-bicarbonate-mediated catalytic activity for hydrogen peroxide dismutation and amino acid oxidation: detection of free radical intermediates.

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