Superoxide generation from

C.M. Tolias, J.C. McNeil, J. Kazlauskate, and E.W. Hillhouse, Superoxide generation from constitutive nitric oxide synthase in astrocytes in vitro regulates extracellular nitric oxide availability. Free Radical Biol. Med. 26, 99-106 (1999). 

VISUALIZATION OF SUPEROXIDE GENERATED FROM COLONIES OF CANDIDA ALBICANS... 

Visualization of Superoxide Generated from Candida albicans... 

Vasquez-Vivar, J., P. Martasek, N. Hogg, B.S. Masters, K.A. Pritchard, Jr., and B. Kalyanaraman (1997). Endothelial nitric oxide synthase-dependent superoxide generation from adriamycin. Biochemistry 36, 11293-11297. 

Superoxide Generation from Nitric Oxide Synthase Role of Cofactors and Protein Interaction... 

Cunningham, M.L., Krinsky, N.I., Giovanajzi, S.M. and Peak, M.J. (1985). Superoxide anion is generated from cellular metabolites by solar radiation and its components. J. Free Rad. Biol. Med. 1, 381-385. 

Tumour necrosis factor provokes superoxide anion generation from neutrophils. Biochem. Biophys. Res. Commun. 137, 1094-1100. 

Hansen, K. and Mossman, B.T. (1987). Generation of superoxide (Oi ) from alveolar macrophages exposed to asbestiform and nonfibrous particles. Cancer Res. 47, 1681-1686. 

Weitzman, S.A. and Graceffii, P. (1984). Asbestos catalyzes hydroxyl and superoxide radical generation from hydrogen peroxide. Arch. Biochem. Biophys. 228, 373-376. 

K. Tanaka, F. Kobayashi, Y. Isogai, and T. Iizuka, Electrochemical determination of superoxide anions generated from a single neutrophil. Bioelectrochem. Bioenerg. 26, 413—421 (1991). 

S. Mesaros, Z. Vankova, A. Mesarosova, P. Tomcik, and S. Grunfeld, Electrochemical determination of superoxide and nitric oxide generated from biological samples. Bioelectrochem. Bioenerg. 46, 33-37 (1998). 

The principle of antioxidant detection is shown in Fig. 17.3. Superoxide was enzymatically produced and dismutated spontaneously to oxygen and H202. Under controlled conditions of superoxide generation such as air saturation of the buffer, optimal hypoxanthine concentration (100 pM) and XOD activity (50mU ml-1) a steady-state superoxide level could be obtained for several min (580-680 s). Since these steady-state superoxide concentrations can be detected by the cyt c-modified gold electrode, the antioxidate activity can be quantified from the response of the sensor electrode by the percentage of the current decrease. 

CL produced in the presence of exogenous NADPH or NADH, which has been studied in Refs. [97,100], may originate from other sources than superoxide generation [90]. In our opinion [98], the data obtained on the basis lucigenin CL measurement, especially with the use of small lucigenin concentrations provide the reliable estimate of superoxide concentration while the use of ESR spin technique underestimates it, particularly in vascular tissue and cells (see Chapter 32). 

Complex I can be regulated by phosphorylation. Demin et al. [28] studied superoxide generation by Complex III using the kinetics model of electron transfer from succinate to cytochrome c. 

Superoxide generation was detected via the NADPH-dependent SOD-inhibitable epinephrine oxidation and spin trapping [15,16], Grover and Piette [17] proposed that superoxide is produced equally by both FAD and FMN of cytochrome P-450 reductase. However, from comparison of the reduction potentials of FAD (-328 mV) and FMN (190 mV) one might expect FAD to be the most efficient superoxide producer. Recently, the importance of the microsomal cytochrome h558 reductase-catalyzed superoxide production has been shown in bovine cardiac myocytes [18]. 

In 1977, Kellogg and Fridovich [28] showed that superoxide produced by the XO-acetaldehyde system initiated the oxidation of liposomes and hemolysis of erythrocytes. Lipid peroxidation was inhibited by SOD and catalase but not the hydroxyl radical scavenger mannitol. Gutteridge et al. [29] showed that the superoxide-generating system (aldehyde-XO) oxidized lipid micelles and decomposed deoxyribose. Superoxide and iron ions are apparently involved in the NADPH-dependent lipid peroxidation in human placental mitochondria [30], Ohyashiki and Nunomura [31] have found that the ferric ion-dependent lipid peroxidation of phospholipid liposomes was enhanced under acidic conditions (from pH 7.4 to 5.5). This reaction was inhibited by SOD, catalase, and hydroxyl radical scavengers. Ohyashiki and Nunomura suggested that superoxide, hydrogen peroxide, and hydroxyl radicals participate in the initiation of liposome oxidation. It has also been shown [32] that SOD inhibited the chain oxidation of methyl linoleate (but not methyl oleate) in phosphate buffer. 

Many transition metal complexes have been considered as synzymes for superoxide anion dismutation and activity as SOD mimics. The stability and toxicity of any metal complex intended for pharmaceutical application is of paramount concern, and the complex must also be determined to be truly catalytic for superoxide ion dismutation. Because the catalytic activity of SOD1, for instance, is essentially diffusion-controlled with rates of 2 x 1 () M 1 s 1, fast analytic techniques must be used to directly measure the decay of superoxide anion in testing complexes as SOD mimics. One needs to distinguish between the uncatalyzed stoichiometric decay of the superoxide anion (second-order kinetic behavior) and true catalytic SOD dismutation (first-order behavior with [O ] [synzyme] and many turnovers of SOD mimic catalytic behavior). Indirect detection methods such as those in which a steady-state concentration of superoxide anion is generated from a xanthine/xanthine oxidase system will not measure catalytic synzyme behavior but instead will evaluate the potential SOD mimic as a stoichiometric superoxide scavenger. Two methodologies, stopped-flow kinetic analysis and pulse radiolysis, are fast methods that will measure SOD mimic catalytic behavior. These methods are briefly described in reference 11 and in Section 3.7.2 of Chapter 3. 

Figure 5.17 Superoxide generation during oxygen release from haemoglobin...

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