Free radical combination reactions involving phenoxyl radicals

Jönsson, Mats; Lind, Johan; Reitberger, Torbjörn; Eriksen, T. E.; Merényi, Gábor

doi:10.1021/j100133a018

Cited by 121 publications

(117 citation statements)

References 4 publications

Supporting

Mentioning

113

Contrasting

Order By: Relevance

“…Others have observed for a range of phenoxyl radicals that the contribution of repair relative to O 2 . addition decreases progressively with increasing reduction potential of the phenol (19). This was explained by the repair reaction occurring by electron transfer (which, in accordance with the Marcus theory, is favored when the difference in reduction potential between the two couples is high).…”

Section: Discussionsupporting

confidence: 61%

“…reacting with the peptide radicals to repair the Tyr. Two mechanisms have been proposed: repair via electron transfer (19) or release of 1 O 2 from an unstable hydroperoxide intermediate (7, 18) (reactions 2 or 4 in Fig. 1b, respectively).…”

Section: No Evidence For Singlet Oxygen Releasementioning

confidence: 99%

“…However, one of their most favored reactions is with O 2 . (5,7,18,19). The reaction has a rate constant several times higher than that for dimerization (7,20) and is favored over dityrosine formation in situations where both tyrosyl and O 2 .…”

mentioning

confidence: 99%

See 2 more Smart Citations

Superoxide-mediated Formation of Tyrosine Hydroperoxides and Methionine Sulfoxide in Peptides through Radical Addition and Intramolecular Oxygen Transfer

Nagy

Kettle

Winterbourn

2009

Journal of Biological Chemistry

View full text Add to dashboard Cite

The chemistry underlying superoxide toxicity is not fully understood. A potential mechanism for superoxide-mediated injury involves addition to tyrosyl radicals, to give peptide or protein hydroperoxides. The rate constant for the reaction of tyrosyl radicals with superoxide is higher than for dimerization, but the efficiency of superoxide addition to peptides depends on the position of the Tyr residue. We have examined the requirements for superoxide addition and structurally characterized the products for a range of tyrosyl peptides exposed to a peroxidase/O 2 . system. These included enkephalins as examples of the numerous proteins and physiological peptides with N-terminal tyrosines. The importance of amino groups in promoting hydroperoxide formation and effect of methionine residues on the reaction were investigated. When tyrosine was N-terminal, the major products were hydroperoxides that had undergone cyclization through conjugate addition of the terminal amine. With non-N-terminal tyrosine, electron transfer from O 2. to the peptide radical prevailed. Peptides containing methionine revealed a novel and efficient intramolecular oxygen transfer mechanism from an initial tyrosine hydroperoxide to give a dioxygenated derivative with one oxygen on the tyrosine and the other forming methionine sulfoxide. Exogenous amines promoted hydroperoxide formation on tyrosyl peptides lacking a terminal amine, without forming an adduct. These findings, plus the high hydroperoxide yields with N-terminal tyrosine, can be explained by a mechanism in which hydrogen bonding of O 2 . to the amine increases is oxidizing potential and alters its reactivity. If this amine effect occurred more generally, it could increase the biological reactivity of O 2 . and have major implications.

show abstract

Section: Discussionsupporting

confidence: 61%

Section: No Evidence For Singlet Oxygen Releasementioning

confidence: 99%

See 1 more Smart Citation

Superoxide-mediated Formation of Tyrosine Hydroperoxides and Methionine Sulfoxide in Peptides through Radical Addition and Intramolecular Oxygen Transfer

Nagy

Kettle

Winterbourn

2009

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…Our experiments showed that typical model oxidants, such as trolox (residue of vitamin E) and catechol (a residue present in flavanoids and other plant antioxidants), efficiently protect guanines from oxidative transformation to other products. Phenoxyl radicals derived from oneelectron oxidation of these antioxidants by neutral guanine radicals can rapidly react with superoxide radicals (49) and provide a second line of defense.…”

Section: Combination Of G(ϫh) ⅐ and O 2 Radicals; Electron Transfermentioning

confidence: 99%

Oxidative DNA Damage Associated with Combination of Guanine and Superoxide Radicals and Repair Mechanisms via Radical Trapping

Misiaszek

Crean

Joffe

et al. 2004

Journal of Biological Chemistry

209

250

View full text Add to dashboard Cite

“…The reaction with oxygen may then be challenged by superoxide at high pH as its reaction with a hydroxycyclohexadienyl adduct should be non-reversible and the reaction rate close to diffusion controlled (cf. reaction of superoxide with phenoxyl-type radicals [36]). If so, a range of alternative reaction pathways are possible and the yield of aromatic ring hydroxylation could be much reduced.…”

Section: Figure 1 Reduction Of Adsorbed Oxygen and Formation Of Ros mentioning

confidence: 99%

Generation of Free OHaq Radicals by Black Light Illumination of Degussa (Evonik) P25 TiO2 Aqueous Suspensions

Liao¹,

Reitberger

2013

Catalysts

View full text Add to dashboard Cite

This work demonstrates how formation of strongly chemiluminescent 3-hydroxyphthalic hydrazide by hydroxylation of non-chemiluminescent phthalic hydrazide can be applied as a selective reaction probe to obtain information on authentic hydroxyl radical, i.e.,• OH aq , formation, in black light illuminated Degussa P25 TiO 2 aerated suspensions in the pH range from 3 to 11. The • OH aq formation was found to be strongly pH dependent. At alkaline pH, the apparent quantum efficiency of • OH aq formation was estimated to be at the ~10 −2 level whereas at acidic pH it was near zero. Addition of phosphate and fluoride ions substantially enhanced the • OH aq production in the acidic pH range. It is suggested that • OH aq -radical formation in TiO 2 photocatalysis can occur by oxidation of hydroxyl ions in the water layer adsorbed on TiO 2 surfaces.

show abstract

Free radical combination reactions involving phenoxyl radicals

Cited by 121 publications

References 4 publications

Superoxide-mediated Formation of Tyrosine Hydroperoxides and Methionine Sulfoxide in Peptides through Radical Addition and Intramolecular Oxygen Transfer

Superoxide-mediated Formation of Tyrosine Hydroperoxides and Methionine Sulfoxide in Peptides through Radical Addition and Intramolecular Oxygen Transfer

Oxidative DNA Damage Associated with Combination of Guanine and Superoxide Radicals and Repair Mechanisms via Radical Trapping

Generation of Free OHaq Radicals by Black Light Illumination of Degussa (Evonik) P25 TiO2 Aqueous Suspensions

Contact Info

Product

Resources

About