Reactive oxygen species Quenching

The evidence available to date indicates that lutein and zeaxanthin could contribute to achieving the last two objectives, namely, the reduction of actinic insults caused by blue light and quenching reactive oxygen species. This follows from the dual presence of xanthophylls in the macula their prereceptoral location and their presence within the outer segments themselves, as discussed in Section 13.5. 

Work conducted by Tiller and Jones (1997) demonstrated that the fluorescence of PAHs decayed over time under both under anoxic and oxic conditions. Typically, however, the presence of dissolved oxygen had a more pronounced influence on baseline fluorescence decay for all the PAHs studied. Moreover, certain PAHs (pyrene and anthracene) were more susceptible to this phenomenon than others. To date a mechanism to explain this phenomenon has not been identified, but it is probably a combination of complex pathways including the reaction of the analyte with reactive oxygen species formed from the excited triplet state DOM and the direct photolysis of the analyte by the excitation light source. Thus, the application of fluorescence quenching for measuring Kdom is probably limited to systems, which can be analyzed under anoxic conditions. 

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). 

Carotenoids are substances able to interact with reactive oxygen species, especially to quench singlet oxygen. Therefore, these compounds are especially... 

DEVELOPMENT OF FIA-CHEMILUMINESCENCE METHODS TO EVALUATE QUENCHING EFFECTS AGAINST REACTIVE OXYGEN SPECIES... 

Fig. 21. In vivo diagnostic application of hyaluronic acid immobilized gold nanoprobes. (A) The fluorescence quenching by nanoparticle surface-energy transfer between Hilyte-647 dye labelled oUgo-HA and gold nanocluster (left) is followed by fluorescence recovery after addition of reactive oxygen species/HAdase which release the dye labeled oUgo-HA fragments. (B) Tail vein injection of GNPs capped with HA conjugates labelled with Hilyte-647 in normal (up) and arthritis (bottom) mice. Adapted from Ref 103. (See Color Plate 43.)...

---