Acid superoxides

Lob2 is in favor of accepting in certain cases the theory advanced by Kekule, who sought by experiments to prove the intermediate formation of the anhydride, while Schall3 assumes the formation of an acid superoxide ... 

In contrast to the acid superoxides, the acid supersulphides are stable compounds. 

In 1993, Stephen B. H. Kent (1945- ) and collaborators used automated peptide synthesis to construct all-D-amino acid superoxide dis-mutase. As expected it folded so as to be the mirror image of the native (all-L) enzyme. This D-protein is equally effective as the native protein in catalyzing the disappearance of superoxide (O2 ), a toxic species, because superoxide is achiral. The potential advantage of this approach is that D-proteins should not be destroyed by natural proteases nor should they ehcit immune responses. 

Substance names Catalyze, phtalocyanines of metals, humic acids. Phenol nature substances, vitamins A, E, C, B, flavonoids. N, S, Se-containing substances, amines, amino acids. Superoxide dismutase (SOD), porphyry metals, cytochrome C... 

Like ascorbic acid, superoxide dismutase (SOD) can also convert superoxide to hydrogen peroxide. However, the extracellular concentration of superoxide dismutase is low. At the normal extracellular ascorbic acid concentration, the vitamin would be expected to remove superoxide more effective than SOD. It is therefore... 

Klapper 1, R Hagstrom, RFine, K Sharp and B Honig 1986. Focusing of Electric Fields in tire Actir e Sit of CuZn Superoxide Dismutase Effects of Ionic Strength and Amino-Acid Substitution. Proteins Structure, Function and Genetics 1 47-59. 

Two classes of antioxidants are known the low-molecular weight compounds (tocopherols, ascorbate, -carotene, glutathione, uric acid and etc.) and the proteins (albumin, transferrin, caeruloplasmin, ferritin, etc.) including antioxidant enzymes (e.g. superoxide dismutase, catalase, glutathione peroxidase). 

Preparation of pure K2O2, Rb202 and CS2O2 by this route is difficult because of the ease with which they oxidize further to the superoxides MO2. Oxidation of the metals with NO has been used but the best method is the quantitative oxidation of the metals in liquid ammonia solution (p. 78). The peroxides can be regarded as salts of the dibasic acid H2O2. Thus reaction with acids or water quantitatively liberates H2O2 ... 

Suzuki, N., etal. (1991). Studies on the chemiluminescent detection of active oxygen species 9-acridone-2-sulfonic acid, a specific probe for superoxide. Agric. Biol. Chem. 55 1561-1564. 

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... 

Similarly, when both the Cp and arene ligands are permethylated, the reaction of 02 with the Fe1 complex leads to C-H activation of the more acidic benzyl bond [57]. When no benzylic hydrogen is present, superoxide reacts as a nucleophile and adds onto the benzene ligand of the FeCp(arene)+ cation to give a peroxocyclohexadienyl radical which couples with a Fe Cp(arene) radical. A symmetrical bridging peroxo complex [(Fe"Cp)2(r 5-C6H60)2] is obtained. The C-H activation reactions of the 19e Fe1 radicals BH can be summarized as follows... 

Unsymmetrical thiosulphinates and thiosulphonates are both oxidized by potassium superoxide in pyridine in the presence of 18-crown-6 ether to produce sulphinic and sulphonic acids and a disulphide, under mild conditions (equation 84)200,201. Sulphinic and sulphonic acids were produced from both the R and R substituents whilst the disulphide was derived only from the sulphenyl side of the reactant. Thus, the reaction mixture contained five products, making the reaction not synthetically useful. Pyrolysis of thiosulphinates also produces mixtures of products, one being the thiosulphonate again this is not a synthetically useful reaction202. 

Oxidant production is measured with the fluorogenic substrate para-hydroxyphenylacetic acid (PHPA) in the presence of superoxide dismutase and peroxidase (9). Under these conditions, superoxide is converted to H2O2 by the superoxide dismutase, and two molecules of PHPA are converted to a fluorescent diadduct by H2O2 and peroxidase. Similar assays have been devised using homovanillic acid (16) or scopoletin (17) instead of PHPA. 

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