Radical superoxide

Figure S.l The enzyme superoxide dismutase (SOD). SOD is a P structure comprising eight antiparallel P strands (a). In addition, SOD has two metal atoms, Cu and Zn (yellow circles), that participate in the catalytic action conversion of a superoxide radical to hydrogen peroxide and oxygen. The eight p strands are arranged around the surface of a barrel, which is viewed along the barrel axis in (b) and perpendicular to this axis in (c). [(a) Adapted from J.S. Richardson. The stmcture of SOD was determined in the laboratory of J.S. and D.R. Richardson, Duke University.)...

Fig. 8.9 Possible mechanisms of the bioluminescence reaction of dinoflagellate luciferin, based on the results of the model study (Stojanovic and Kishi, 1994b Stojanovic, 1995). The luciferin might react with molecular oxygen to form the luciferin radical cation and superoxide radical anion (A), and the latter deproto-nates the radical cation at C.132 to form (B). The collapse of the radical pair might yield the excited state of the peroxide (C). Alternatively, luciferin might be directly oxygenated to give C, and C rearranges to give the excited state of the hydrate (D) by the CIEEL mechanism. Both C and D can be the light emitter.

Fridovich, I. (1986). Biological effects of the superoxide radical. Arch. Biochem. 247 1-11. 

Nakano, M. (1990). Determination of superoxide radical and singlet oxygen based on chemiluminescence of luciferin analog. Method. Enzymol. 186 585-591. 

When the iron sandwich complex bears an arene substituent with at least one benzylic hydrogen, the acidity of the latter is enhanced by the 7t-complexation to the 12e fragment FeCp+. The pKa of the conjugate acid of superoxide radical... 

A parallel set of determinations was done with Cu2+ added, since this metal ion has been reported to oxidize the superoxide radical ion very rapidly. Thus, with added Cu2+ the first reaction proceeded as shown, but the second was replaced by... 

Pavlov, A.R., Revina, A.A., Dupin, A.M., Baldyrev, A.A., Yaropolow, A.I. (1993). The mechanism of interaction of camosine with superoxide radicals in water solutions. Biochem. Biophys. Acta 1157,304-314. 

Walkup, L.K. Kogoma, T. (1989). E. coli proteins inducible by oxidative stress mediated by the superoxide radical. J. Bacteriol. 171, 1476-1484. 

Fig. 3. a) First order plot of oxygen uptake in the Methylene-blue (MB)-sensitized photooxidation of GA 8.4 pM and 1.3 mM histidine (control) in phosphate buffer pH 7. b) Percentage radical scavenging activity for the control molecule Trolox and GA at pH 7.4 in phosphate buffer 10 mM (hydroxyl radical) and pH 10 in sodium carbonate buffer 50 mM (anion superoxide radical). 

Nitric oxide has also been implicated in PD. Thus animals with MPTP-induced Parkinsonism not only show extensive gliosis in the substantia nigra (like humans) in which the glial cells produce NO, but Liberatore and colleagues have found that in iNOS (inducible nitric oxide synthase) knock-out mice the toxicity of MPTP is halved. Since NO releases iron from ferritin and produces toxic peroxinitrate in the presence of superoxide radicals it could accelerate, even if it does not initiate, dopaminergic cell death (see Hirsch and Hunot 2000 for further details). 

Nagata K, H Yu, M Nishikawa, M Kashiba, A Nakamura, EE Sato, T Tamura, M Inoue (1998) Helicobacter pylori generates superoxide radicals and modulates nitric oxide metabolism. J Biol Chem 273 14071-14073. 

Superoxide dismutase is important for the detoxification of the superoxide radical (O2 ) by reacting with protons to produce H2O2 202 + 2H+ —>62 + H2O2. Although the enzyme generally contains Mn and Fe, or Cu and Zn, the enzyme from Streptomyces seoulensis contains Ni(HI) (Wuerges et al. 2004). 

Absorption of a light quantum leads to an electron-hole pair Eq. (19). The electron reacts with an adsorbed oxygen molecule Eq. (20), and the hole semi-oxidizes a sulfide anion at the surface Eq. (21). Further oxidation of the sulfide anion occurs by O and O2 Eq. (22). The number of Cd ions formed equals that of the sulfate anions The oxidation of illuminated CdS powders was investigated by measuring the consumption and by detecting the superoxide radical,, by an ESR spin trapping method... 

Not all oxidants formed biolc cally have the potential to promote lipid peroxidation. The free radicals superoxide and nitric oxide [or endothelium-derived relaxing aor (EDRF)] are known to be formed in ww but are not able to initiate the peroxidation of lipids (Moncada et tU., 1991). The protonated form of the superoxide radical, the hydroperoxy radical, is capable of initiating lipid peroxidation but its low pili of 4.5 effectively precludes a major contribution under most physiological conditions, although this has been suggested (Aikens and Dix, 1991). Interestingly, the reaction product between nitric oxide and superoxide forms the powerful oxidant peroxynitrite (Equation 2.6) at a rate that is essentially difiiision controlled (Beckman eta/., 1990 Huie and Padmaja, 1993). 

Jessup, W., Simpson, J.A. and Dean, RT. (1993). Does superoxide radical have a role in macropha mediated oxidative modification of LDL Atherosclerosis 99, 107-120. 

The heart has a relatively low catalase activity, which, together with the superoxide dismutase (SOD) system, acts to remove hydrogen peroxide and superoxide radicals. In addition, in man, dietary vitamin C plays an important role in the reduction of vitamin E, an intrinsic antioxidant component of biological membranes (Chen and Thacker, 1986 Niki, 1987). Both vitamins C and E can also react directly with hydroxyl and superoxide radicals (HalliwcU and Gutteridge, 1989 Meister, 1992). 

Chan, P.H. and Fishman, R.A. (1980). Transient formation of superoxide radicals in polyunsaturated fatty acid-induced brain swelling. J. Neurochem. 33, 1004-1007. 

Does 3,5-dibromo-4-nitrosobenzene sulphonate spin trap superoxide radicals Biochem. Biophys. Res. Commun. 200, 1-16. 

Kono, Y. and Friedovich, I. (1982). Superoxide radical inhibits catalase. J. Biol. Chem. 257, 5751-5754. 

Shimizu, N., Kobayashi, K. and Hayashi, K. (1984). The reaction of superoxide radical with catalase. J. Biol. Chem. 259, 4414-4418. 

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