Scavenging effects

The relinking (14) and self-healing film (3) theories require chemical interaction between the antiozonant and ozonized mbber. The evidence for these interactions is meager (35,36). Overall, there seems to be no clear evidence in the Hterature for PDA derivatives becoming attached to mbber chains as a result of ozone attack. Much fundamental work in this area remains to be done, however. It seems clear at this point that any antiozonant—mbber interaction must be much less important than the scavenging effect of the antiozonant. In summary, the scavenger model is beheved to be the principal mechanism of antiozonant action. Ozone—antiozonant reaction products form a surface film that provides additional protection (37). 

The results showed that the presence of oxygen caused a decrease in the yield of As 03 and — As0j> and an increase (not equal to the sum of the other decreases) in >As0. The decrease in clearly due to thermal scavenging effects, while the increase in As0 was ascribed to scavenging reactions such as... 

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). 

It has been proposed that the capacity of antiinflammatory drugs to scavenge and inhibit ROM production is pertinent to their therapeutic effect (Hal-hwell et al., 1988). NSAIDs, namely indomethacin, inhibit superoxide generation by stimulated guinea-pig macrophages (Oyanagui, 1976) and the scavenging effects of PMN-derived ROMs by the sulphasalazine... 

Scavenging effect of 5-aminosalicylic acid on neutrophil-derived oxidants. Biochem. Pharmacol. 41, 1001-1006. 

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... 

A common form of EDTA used as a preservative is calcium disodium EDTA (CaNa2EDTA). What metals will this form of the sequestrant scavenge effectively The dissolution of the solid will yield calcium ions, sodium ions, and the EDTA anion. Any metal more effectively complexed than calcium will be readily scavenged, including all ions listed in Table 9.1 except silver (Ag+) and magnesium (Mg2+). (In the absence of the calcium counterion, as in the case of the acid form of EDTA, chelation of calcium in the body can occur. In fact, EDTA administered orally is an FDA-approved treatment for calcium deposits in the bloodstream that lead to cardiovascular disease.) Citric acid (Fig. 9.3.3) is another sequestrant of metal ions in foodstuffs. 

When the flow through the CNC was exhausted outside of the laboratory, we observed particle formation at higher SOp concentrations as expected (Table II). To prove that the radical scavenger effect is reproducible, another radical scavenger (92 ppb nitric oxide) was used in the presence of 110 ppb SOp concentration and 2% humidity, and the supression in particle formation was observed. Another possible mechanism that supressed the particle formation is that more neutralization of polonium ions occurred at the higher humidities and thus ion-induced nucleation would be suppressed. 

Re-formation of water must be considered somewhat arbitrarily. However, these models have been generally useful in delineating LET and scavenger effects on the total molecular yield. 

Selenoureas are prepared by reaction of isoselenocyanates with amines, or by reaction of carbodiimides with a mixture of LiAlH4/Se and by reaction of cyanamides with LiAlH4/Se.267 272 The tyrosinase inhibitory activity and superoxide radical scavenger effect of selenoamides and selenoureas have been investigated (Scheme 84).273 275... 

Jia Z, Tang M and Wu J. 1999. The determination of flavonoid contents in mulberry and their scavenging effects on superoxide radicals. Food Chem 64 555-559. 

In a study by Krishnamoorthy et al.,4s indigenous or added water led to marked increases in CO conversion for 12.7 wt% Co/Si02. The authors suggest that the water effects do not arise from new pathways introduced by water, by scavenging effects of H20 on the concentration of site-blocking unreactive intermediates, or by removing significant CO transport restrictions. As a result, they were left with only the possibility that water influences the relative concentration of the active and inactive forms of carbon, present at low concentrations on Co surfaces. The mechanism by which such effects occur was unclear. 

Cheng F, Yang X, Zhu H et al. (2000) Synthesis of oligoadducts of malonic acid C60 and their scavenging effects on hydroxyl radical. J Phys Chem Solids. 61 1145-1148. 

Rationalise the spectral, kinetic and scavenging effects in terms of the production of Table 3.5). 

Even though HO2 radicals are generated by the scavenging effect, they are much less reactive than OH radicals Bielski et al. 1985 Pignatello 1992). 

The radical scavenging methods require the general caution that the stoichiometry of the reaction between scavenger and radical must be established. A problem with some scavengers is that their reaction with radicals may not be quantitative. The DPPH radical is an extremely efficient scavenger in many systems. It completely stops vinyl acetate and styrene polymerizations even at concentrations below 10 4M [Bartlett and Kwart, 1950]. However, the scavenging effect of DPPH is not universally quantitative for all monomers. 

Radical scavenging effect. Seed oil, in cell culture, was active on astrocytes vs peroxide radical scavenging, IC50 27461 ppm . Spasmogenic activity. Methanol (70%) extract of the seed, administered to guinea pigs at a dose of 1 mg/mL, was active on the uterus and ileum. The effect was abolished... 

The experiments were carried out using the subpicosecond pulse radiolysis system [77] described in Sec. 10.2.2 ( Subpicosecond Pulse Radiolysis ). Considering the signal intensity and the degradation of the time resolution, a sample cell with the optical length of 2 mm was mostly used. The sample was saturated by Ar gas to eliminate the scavenging effect by the remaining O2 gas. 

Lou, H. et al.. Polyphenols from peanut skins and their free radical-scavenging effects. Phytochemistry, 65, 2391, 2004. 

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