Formate radical scavenger

Weiss (18), Kevan, Davis, and Libby (3, 9) proposed ion-molecule reactions to explain dimer formation. Radical scavenging studies have lead Falconer and Salovey (4, 5, 12) to the conclusion that radical reactions produce at least 40% of the dimer. Other authors (17, 19) give much more importance to radical processes. 

Vitamin E can also act as an antioxidant (qv) in animals and humans alone or in combination with vitamin C (qv). Both are good free-radical scavengers with the vitamin C acting to preserve the levels of vitamin E (35). Vitamin E in turn can preserve the levels of vitamin A in animals (13). It has been shown that vitamin E reduces the incidence of cardiovascular disease (36—39). This most likely results from the antioxidant property of the vitamin which inhibits the oxidation of low density Hpoproteins (LDLs) (40—42). The formation of the oxidized LDLs is considered important in decreasing the incidence of cardiovascular disease (43). 

Well before the advent of modern analytical instruments, it was demonstrated by chemical techniques that shear-induced polymer degradation occurred by homoly-tic bond scission. The presence of free radicals was detected photometrically after chemical reaction with a strong UV-absorbing radical scavenger like DPPH, or by analysis of the stable products formed from subsequent reactions of the generated radicals. The apparition of time-resolved ESR spectroscopy in the 1950s permitted identification of the structure of the macroradicals and elucidation of the kinetics and mechanisms of its formation and decay [15]. 

Nishimura and coworkers57-59 studied the y-radiolysis of aqueous solutions of sulfoxide amino acids. Sulfoxide amino acids are the precursors of the flavors of onions (S-propyl-L-cysteine sulfoxide, S-methyl-L-cysteine sulfoxide and S-(l-propenyl)-L-cysteine sulfoxide) and garlic (S-allyl-L-cysteine sulfoxide). In studies on sprout inhibition of onion by /-irradiation it was found that the characteristic flavor of onions became milder. In the y-radiolysis of an aqueous solution of S-propyl-L-cysteine sulfoxide (PCSO)57,58 they identified as the main products alanine, cysteic acid, dipropyl disulfide and dipropyl sulfide. In the radiolysis of S-allyl-L-cysteine sulfoxide (ACSO) they found that the main products are S-allyl-L-cysteine, cysteic acid, cystine, allyl alcohol, propyl allyl sulfide and diallyl sulfide. The mechanisms of formation of the products were partly elucidated by the study of the radiolysis in the presence of N20 and Br- as eaq - and OH radicals scavengers, respectively. 

Moorhouse, C.P., Halliwell, B., Grootveld, M. and Gutteridge, J.M.C. (1985). Cobalt(ll) ion as a catalyst of hydroxyl radical and possible crypto-hydroxy radical formation under physiological conditions. Differential effects of hydroxyl radical scavengers. Biochem. Biophys. Acta 843, 261-268. 

It has long been recognized that ascorbate levels are low in patients with RA (Lunec and Blake, 1985) and ascorbate is predominantly found in the dehydro form. The presence of increased dehydroascorbate has been suggested to indicate its rapid oxidation by stimulated PMNs (Halliwell and Gutteridge, 1990). When ascorbate concentrations are lower than about 20 /tmol/1, as can occur in rheumatoid synovial fluid, the Fe(III) reducing effects of ascorbate outweigh its radical-scavenging effects. Ascorbate then causes increased OH formation and promotes lipid peroxidation (Blake et al., 1981). 

Since the mixed pinacol is formed in the presence of the ketyl radical scavenger camphorquinone, its formation must occur under conditions where the ketyl radicals are not available for scavenging, that is, in a solvent cage. Since benzpinacol is not observed under these conditions, its formation must occur outside of the initial solvent cage. The following mechanism is proposed ... 

The yield of trans product (18) is decreased by the presence of a radical scavenger such as 1,1-diphenylethylene and increased by dilution of the reactants with methylene chloride or butane, indicating this product to result from the triplet carbene. A heavy-atom effect on the carbene intermediate was observed by photolysis of a-methylmercuridiazoacetonitrile. With c/s-2-butene as the trapping agent either direct photolysis or triplet benzophenone-sensitized decomposition results in formation of cyclopropanes (19) and (20) in a 1 1 ratio ... 

For the sonochemical mineralization of reactive dye Cl Reactive Black 5 with 20, 279 and 817 kHz irradiation, the discoloration and radical formation both are directly dependent upon ultrasonic frequency, acoustic power and irradiation time and indirectly on the number of free radicals thus generated, as their suppression decreased the discoloration rate due to radical scavenging effect. Although ultrasound alone is capable of decolorizing Reactive Black 5 but inefficient in mineralization as only 50% degradation was observed after 6 h of ultrasonic irradiation [121]. The sonochemical... 

It has been found that the "unattached" fraction is an ultrafine particle aerosol with a size range of 0.5 to 3 nm. In order to initiate studies on the formation mechanism for these ultrafine particles, a series of experiments were made in the U.S. Bureau of Mines radon chamber. By introducing SO into the chamber, particles were produced with an ultrafine size distribution. It has been found that the particle formation mechanism is supressed by the presence of radical scavengers. These experiments suggest that radiolysis following the decay of Rn-222 gives rise to the observed aerosol and the properties of the resulting aerosol are dependent on the nature and the amount of reactive gas present. 

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