Reactive oxygen species quenching mechanism

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. 

X 10 mol of DNA. The proposed mechanism for the quenching effect is ascribed to the interaction between luminol and DNA and the elimination of reactive oxygen species (ROSs) by DNA. The dsDNA could efficiently quench the ECL of luminol in the pH range of 6.5-11. The DNA sensor furnishes exceptional stability and reproducibility and could potentially serve as a powerful tool for the label-free investigation of dsDNA and might encourage the further development and applications in clinical practice, medicine, and basic research [39]. 

A large range of free radicals and other reactive oxygen species (ROS) can be produced biologically and in vivo and a variety of antioxidant species quench these ROS. Pulse radiolysis and laser flash photolysis are useful techniques for producing these radicals and ROS and for studying their reaction mechanisms. 

Although the exact mechanism of the fluorenone formation is not known, it is believed that the monoalkylated fluorene moieties, present as impurities in poly(dialkylfluorenes), are the sites most sensitive to oxidation. The deprotonation of rather acidic C(9)—H protons by residue on Ni(0) catalyst, routinely used in polymerization or by metal (e.g., calcium) cathode in LED devices form a very reactive anion, which can easily react with oxygen to form peroxides (Scheme 2.26) [293], The latter are unstable species and can decompose to give the fluorenone moiety. It should also be noted that the interaction of low work-function metals with films of conjugated polymers in PLED is a more complex phenomenon and the mechanisms of the quenching of PF luminescence by a calcium cathode was studied by Stoessel et al. [300],... 

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