Reactive oxygen species quencher

General descriptors may be related to the metabolism responses in the biofilm. Biofilm algae have several mechanisms to counterbalance the damage caused by the toxicants. Environmental stress produces oxidative damage in the cells, which can be tracked down by means of the analysis of many enzymes (superoxide dismutase, catalase, peroxidase, etc.) that function as effective quenchers of reactive oxygen species (ROS). 

On the contrary to the DCA-sensitized conditions, where superoxide is involved as the reactive oxygen species, the TBCHD-sensitized reactions, as expected, are not quenched by BQ, an efficient superoxide ion quencher. In fact, no superoxide ion can be formed in the medium, owing to the highly unfavorable electron-transfer process from the radical anion (TBCHD ) to molecular oxygen (endothermic by 1.21 eV). 

In order to determine the multiplicity of the reactive species, the photodimerization was carried out in the presence of the triplet quenchers oxygen and ferrocene. The results of these experiments are shown in Table 10.4.<41) It is obvious that the presence of oxygen exerts a large quenching effect on the production of the tram dimer and a smaller but significant effect on the formation of the cis dimer (the formation of tram dimer is decreased by oxygen by a factor of 25, while the cis dimer is decreased by a factor of 1.2). As with oxygen, the production of the tram dimer was quenched in the... 

Nitroarenes, on the other hand, are strong electron acceptors and easily undergo one-electron reduction (12, 13). Thus, nitrobenzene, to cite one example, has been customarily used as an effective quencher in chain reactions involving radical anion intermediates, such as in SRN1 reactions (3). Under different conditions, nitroarene radical anions are reactive species. In particular, Zinin (14) reported that treatment of nitroarenes with hot alkaline alcoholic solutions results in products of reduction, mainly the azoxy derivative (equation 2). These complex multistep processes involve nitroarene radical anion intermediates and are quite effectively inhibited by oxygen (10, 15, 16). In 1964, Russell et al. (17) wrote that apparently much of the chemistry of aromatic nitro, nitroso and azo compounds in basic solution involves electron-transfer processes . 

Various carbonyl compounds and decomposition products of methyl linolenate hydroperoxides were tested for their interaction with DNA by measuring fluorescence in the presence of ferric chloride and ascorbic acid. 2,4-Alkadienals and 2,4,7-decatrienals were among the most active decomposition products of linolenate hydroperoxides (Table 5.8). To determine the type of reactive species involved in fluorescence formation with DNA, the effect of free radical antioxidants and a singlet oxygen quencher were examined. )3-Carotene, a-tocopherol and phenolic antioxidants strongly inhibited DNA fluorescence formed by decomposition of linolenate hydroperoxides in the presence of ferric chloride and ascorbic acid (Table 5.9). These results indicate that singlet oxygen and free radical species are important intermediates in the interaction of linolenate hydroperoxides with DNA in the presence of iron and ascorbic acid. 

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