Super-oxides

The reaction mechanisms associated with pathways (A) and (B) may share In common such adsorbed Intermediates as peroxide, super-oxide and their corresponding protonated forms. The distinction between pathways (A) and (B) can become therefore a matter of whether an Intermediate such as peroxide (H02 ) desorbs In significant quantities or not for example,... 

IB Afanas ev. In Super oxide Ion Chemistry and Biological Implications. Vol 1. CRC Press, Boca Raton, FL, Chaper 10, 1989. 

Photolysis Abiotic oxidation occurring in surface water is often light mediated. Both direct oxidative photolysis and indirect light-induced oxidation via a photolytic mechanism may introduce reactive species able to enhance the redox process in the system. These species include singlet molecular O, hydroxyl-free radicals, super oxide radical anions, and hydrogen peroxide. In addition to the photolytic pathway, induced oxidation may include direct oxidation by ozone (Spencer et al. 1980) autooxidation enhanced by metals (Stone and Morgan 1987) and peroxides (Mill et al. 1980). 

In lung alveolar, the super oxide and nitric oxide (formed as a result of inflammation and/or cigarette smoking) combine to form peroxyni-trile. The peroxynitrile may affect nitration of a tyrosine residue near the... 

The electrochemical properties of immobilized copper, zinc superoxide dismutase, and their interaction with super oxide radicals were investigated [474]. 

Chen C, Korshunov V, Massett M, Yan C, Berk B (2007) Impaired vasorelaxation in inbred mice is associated with alterations in both nitric oxide and super oxide pathways. J Vase Res 44(6) 504-512... 

If a large amount of the toxic substance is present, then the detoxication processes present are overwhelmed. Excess super oxide is produced, reduced GSH and NADPH are depleted, and hydroxyl radicals and singlet oxygen are formed. This is the condition known as oxidative stress (see also below this chapter). As well as causing lipid peroxidation, ROS will also cause DNA damage and damage to proteins. 

Preparation.—(1) From Perdisulphates.—In 1878 Berthelot noticed that the solution obtained by adding sulphur heptoxide (p. 180) to water oxidised potassium iodide almost instantaneously, and in 1889 Traube10 observed that an electrolysed (anodic) solution of sulphuric acid possessed the same property, which he attributed to the presence of a super-oxide S04 (cf. p. ISO). The reaction with potassium iodide cannot have been due to perdisulphuric acid, because this liberates iodine quite slowly. In 1898 Caro obtained a similar oxidising solution... 

Now that we have seen that dioxygenyl compounds can be prepared, we might be interested in preparing the exotic and intriguing compound dioxygenyl super-oxide, OjOJ. Using methods similar to those discussed above, we can set up a... 

The oxidation stales may occasionally be ambiguous—the adduct in Eq. 19.7 may be formulated as hemeiiiy-dioxygcn or as heme 111 U-super oxide. See Problem 19.21. 

Other di-p.-oxo MnIIIMnIV complexes, also models for the inactive, super-oxidized Mn catalase, show catalase activity. They may be only precursors for other species with different oxidation states. For example, a series of di- J,-oxo MnmMnIV complexes of L13 (L13 = substituted bis(pyridylmethyl)ethylenedi-amine ligands) [103d] efficiently catalyze the disproportionation of H202 in neutral aqueous media. The activity increases with increasing electron-withdrawing character of the substituents but decreases with the steric bulkiness of substituent X, reaching zero for complex 62 (Figure 22). 

Wang, J., Xu, G., Gonzales, V., Coonfield, M., Fromholt, D., Copeland, N. G., et al. (2002) Fibrillar inclusions and motor neuron degeneration in transgenic mice expressing super oxide dismutase 1 with a disrupted copper-binding site. NeurobiolDis 10, 128-138. 

In addition to the direct absorption as a biological hazard, UV can have additional indirect effects on organisms.26,27 A number of UV photochemical reactions occur in solutions, both within cells and in the external aquatic environment. In the presence of UV, water itself is hydrolyzed, producing hydroxyl ions. Related reactions involving dissolved substances and mediated by UV lead to the formation of peroxides, super oxide, and other radicals. These reactive products are toxic by causing oxidative damage to biological molecules.28-31... 

Electron spin resonance (ESR) study has demonstrated that etodolac (l,8-diethyl-l,3,4,9-tetrahydropyrano-[3,4-b]indole-l-acetic acid) and indomethacin had direct super oxide scavenging activity [99]. 

The most active acid-base pairs of the surface (presumably those exposed on edges, steps, and corners) are able to abstract hydrogen from olefinic hydrocarbons (257) with formation of hydroxyl groups (detected by IR) and allyl anionic species (detected by UV/VIS spectroscopy). Subsequent contact with O2 leads to the formation of super oxide O2 ions (revealed by EPR spectroscopy). A similar interaction with cyclopentadiene leads to surface Cp and OH- groups (202). 

An example of free radical formation is molecular oxygen, which can accept electrons from a variety of sources to produce reactive oxygen species (ROS) such as the superoxide radical, the hydroxyl radical, and the nitric oxide radical. The superoxide anion radical is formed when one electron is taken up by one of the 2p orbitals of molecular oxygen. Certain drugs and other xenobiotics have the capacity to undergo so-called redox cycles, whereby they provide electrons to molecular oxygen and form super oxide. 

Fig. 2. Representative coronal sections of a normothermic and a hypothermic animal 2 mo after 2-h MCAO. Although there is no tissue left in the infarcted area of the normothermic animal, the periinfarct zone still shows reactive astrocytes expressing glial fibrillary acidic protein (GFAP) and manganese-super-oxide dismutase (SOD2) which can be seen as a dark rim around the infarcted area. The hypothermia-treated animal shows a significantly smaller infarct.

A. A. Frimer, Organic Reactions Involving Super Oxide Anion, in The Chemistry of Functional Groups, Peroxides, Ed. S. Patai, Wiley, New York (1983), Ch. 14. 

The existence of this HiPIP-type structure was the starting point of an interesting development in the study of the iron-sulfur active center. X-ray crystallography showed that there is little difference between the 4Fe-4S cluster in a ferredoxin (E0 = —400 mV) and in HiPIP (E0 = +350 mV). This anomaly was elucidated by the so-called C state hypothesis of Carter et al. (7) (Figure 3), in which the existence of a super-reduced HiPIP and a super-oxidized ferredoxin was postulated. The super-reduced HiPIP was shown to exist by Cammack (8) utilizing 80% DMSO (dimethylsulfoxide) to distort the protein environment of HiPIP. In this case a super-reduced HiPIP with EPR signal similar to a... 

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