Carbon radical anion

Weak to moderate chemiluminescence has been reported from a large number of other Hquid-phase oxidation reactions (1,128,136). The Hst includes reactions of carbenes with oxygen (137), phenanthrene quinone with oxygen in alkaline ethanol (138), coumarin derivatives with hydrogen peroxide in acetic acid (139), nitriles with alkaline hydrogen peroxide (140), and reactions that produce electron-accepting radicals such as HO in the presence of carbonate ions (141). In the latter, exemplified by the reaction of h on(II) with H2O2 and KHCO, the carbonate radical anion is probably a key intermediate and may account for many observations of weak chemiluminescence in oxidation reactions. 

XOR is a cytoplasmic enzyme and a ready source of electrons for transfer to molecular oxygen to form reactive oxygen species such as superoxide and peroxide. It is therefore thought to be involved in free radical-generated tissue injury and has been implicated in the pathogenesis of ischemia-reperfusion damage. Moreover, it has recently been implicated in the production of peroxynitrite (89), and carbonate radical anion (92), both potent biological oxidants. Its exact role in lipid peroxidation, inflammation, and infection needs... 

Bonini MG, Miyamoto S, Di Mascio P, et al. Production of the carbonate radical anion during xanthine oxidase turnover in the presence of bicarbonate. J Biol Chem 2004 279(50) 51836-51843. 

Guanine is the most easily oxidizable natural nucleic acid base [8] and many oxidants can selectively oxidize guanine in DNA [95]. Here, we focus on the site-selective oxidation of guanine by the carbonate radical anion, COs , one of the important emerging free radicals in biological systems [96]. The mechanism of COs generation in vivo can involve one-electron oxidation of HCOs at the active site of copper-zinc superoxide dismutase [97, 98], and homolysis of the nitrosoperoxycarbonate anion (0N00C02 ) formed by the reaction of peroxynitrite with carbon dioxide [99-102]. 

Augusto O, Bonini MG, Amanso AM, Linares E, Santos CCX, de Menezes SL (2002) Nitrogen dioxide and carbonate radical anion two emerging radicals in biology. Free Rad Biol Med 32 841-859... 

M.G. Bonini et al., Direct EPR detection of the carbonate radical anion produced from peroxynitrite and carbon dioxide. J. Biol. Chem. 274, 10802-10806 (1999)... 

C. Crean et al., Oxidation of guanine and 8-oxo-7, 8-dihydroguanine by carbonate radical anions Insight from oxygen-18 labeling experiments. Angew. Chem. Int. Ed. 44, 5057-5060 (2005)... 

Surprisingly, in separate experiments, the removal of benzene and toluene from groundwater were relatively unaffected by solution pH [54], despite the fact that the groundwater contained carbonate/bicarbonate alkalinity. It was postulated that the carbonate radical anion [product of Eqs. (89) and (90)] may also degrade these solutes at high solution pHs. 

Similarly, hydroxyl radicals oxidize carbonate anions in water according to Eq. 6-4 generating carbonate radical anions. 

Again, the challenge involves a suitable detection system. As illustrated in Fig. 1, many radicals produced upon pulse irradiation of an aqueous system have UV/Vis absorption bands that can be monitored. Clearly, it is suitable to directly follow absorbance changes in the hydrated electron and the carbonate radical anion, with absorption maxima of 715 nm and 600 nm respectively, through the use of an UV/vis spectrophotometer with fast response time. The OH radical. 

The acid-base equilibria between carbonate/bicarbonate/carbon dioxide clearly show that in vivo systems sufficient amounts of CO2 will be present such as to allow reactions to occur and point out the relevance of the reactivity of COj with biologically significant compounds. The carbonate radical anion is a strong oxidant the reacts by either H-atom abstraction or electron transfer (Eo(C03, H /HCOj) = 1.78V, where the former is generally slower than the latter. 

The reactivity of carbonate radical anion, CO , with amino acids in neutral aqueous solution is not high with k = 10 M s for amino acids with aliphatic side chains and somewhat higher for amino acids with sulfur moieties, k = (10 -10 ) M" s" The reactivity of aromatic moieties vary considerably but indole rings tend to react most rapidly with k 10 M s Hydrogen abstraction likely occurs through an... 

CuZnSOD has been demonstrated to act as a peroxidase, oxidizing various substrates, among them nitrite (to NO2) [57] and relatively bulky molecules such as 5,5-dimethyl- 1-pyrroline N-oxide (DMPO to DMPO-OH), tyrosine (to dityrosine) or 2,2 -azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS to a cation radical). However, the enzyme becomes inactivated in the presence of H2O2. Apparently, hydrogen peroxide reduces Cu- at the active site of the enzyme. Subsequent reaction of H2O2 with Cu generates a potent oxidant (Cu+-0 or Cu + CH) that can attack the adjacent histidine residue and thus inactivate the enzyme, or oxidize an alternative substrate [3]. Most authors assume that the mechanism of the peroxidative action of CuZnSOD, significantly accelerated in the presence of bicarbonate, consists in oxidation of bicarbonate to a carbonate radical anion able to oxidize other substrates [58,59] ... 

Joffe, A., Geacintov, N.E., and Shafirovich, V. (2003) DNA lesions derived from the site-selective oxidation of guanine by carbonate radical anions. Chem. Res. Toxicol., 16, 1528-1538. 

Among the oxyl radicals that are believed to be generated at sites of inflammation, hydroxyl radicals [13] and carbonate radical anions [14] can directly react with DNA to produce irreversible damage of nucleic acid bases. 

The nitrosoperoxycarbonate anion is highly unstable and decomposes to form nitrogen dioxide and carbonate radical anions with the yield y 0.33 [21] ... 

The photolysis of carbonatotetrammine Co(III) complexes [37], [Co(NH3)4C03]+ can be used for the generation of carbonate radical anions. In this method, the UV irradiation of the [Co(NH3)4C03]+ complexes in aqueous solutions induces charge transfer from the coordinated CO] anions to Co(III), followed by a rapid hydrolysis of the Co(II) complex and the formation of free CO radicals [48-50] ... 

Lilie, J., Henglein, A., and Hanrahan, R. J. (1978) Reactions of the carbonate radical anion with organic and inorganic solutes in aqueous solution, paper presented at 176th meeting of American Chemical Society, Miami Beach, Florida. 

In freshwaters, where the Br concentrations are typically far lower, -OH may react either with bicarbonate, carbonate, or dissolved organic matter, depending on the relative concentrations of these species. Reactions with bicarbonate and carbonate produce either the bicarbonate radical, -HCOs, or the carbonate radical anion, COj the pKa of the acid form is about 7.6 (Eriksen et al., 1985). 

Replacement of acetic acid by another hydroxyl radical scavenger, bicarbonate, resulted in no accumulation of peroxide (Figure O, seemingly supporting Case II. Yet the stoichiometry of the peroxide photolysis experiments (Table I) suggests that the scavenging product, carbonate radical anion (Equation 11),... 

In aqueous solution, especially in cellular environments, the carbonate radical anion (CO3) is produced from the reaction between the ubiquitous carbon dioxide and peroxonitrite (ONOO ), which is an instable intermediate (Fig. 5.25) in NO reduction and first forms as an CO2 adduct nitrosoperoxocarboxylate, which then decomposes ... 

Armstrong, D. A., W. L. Waltz and A. Rauk (2006) Carbonate radical anion - thermochemistry. Canadian Journal of Chemistry 84, 1614-1619 Arneth, A., R. K. Monson, G. Schurges, (j. Niinemets and P. I. Palmer (2009) Why are estimates of global terrestrial isoprene emissions so similar (and why is this not so for monoterpenes) Atmospheric Chemistry and Physics 8, 4605-4620 Arnts, R. R., W. B. Petersen, R. L. Seila and B. W. Gay Jr. (1982) Estimates of alpha-pinene emissions from a loblolly pine forest using an atmospheric diffusion model. Atmospheric Environment 16, 2127-2137... 

Yadav A, MishraPC (2011) Quantum theoretical study of mechanism of the reaction between guanine radieal eation and carbonate radical anion formation of 8-oxoguanine. Int J Quantum Chem 112 2000-2008... 

Joffe A, Geacintov NE, Shafirovich V (2003) DNA lesions derived from the site selective oxidation of guanine by carbonate radical anions. Chem Res Toxicol 16 1528 1538 Masuda M, Suzuki T, Friensen MD, Ravanat JL, Cadet J, Pignattelli B, Nishino H, Ohshi-ma H (2001) Chlorination of guanosine and other nucleosides by hypochlorous acid and myeloperoxidase of activated human neutrophils catalysis by nicotine and trimethylamine. J Biol Chem 276 40486 10496... 

IR and Raman spectra gave quite detailed assignments for [HC(ox)(OMe)], where X = H or D ox = oxalato. TR data were reported for the carbonate radical anion, COs" - the data were consistent with C2V symmetryThe IR spectrum of matrix-isolated (COF)2 (oxalyl fluoride). This showed that a cis/trans mixture was present, (6). Detailed assignments were given with the aid of low-temperature Raman spectra. " ... 

G. Ferrer-Sueta, D. Vitturi, I. Batinic-Haberle, I. Fridovich, S. Goldstein, G. Czapski, and R. Radi. Reactions of manganese pophyrins with peroxynitrite and carbonate radical anion. J.Biol.Chem. 278 (30) 27432-27438,2003. 

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