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Daghastanli NA, Itri R, Baptista MS: Singlet oxygen reacts with 2',7'-dichlorodihydrofluorescein and contributes to the formation of 2',7'-dichlorofluorescein. Photochem Photobiol. 2008 Sep-Oct;84(5):1238-43. Epub 2008 Apr 12.
There are controversial reports in the literature concerning the reactivity of singlet oxygen ((1) O (2)) with the redox probe 2',7'-dichlorodihydrofluorescein (DCFH). By carefully preparing solutions in which (1) O (2) is quantitatively generated in the presence of DCFH, we were able to show that the formation rate of the fluorescent molecule derived from DCFH oxidation, which is 2',7'-dichlorofluorescein (DCF), increases in D (2) O and decreases in sodium azide, proving the direct role of (1) O (2) in this process. We have also prepared solutions in which either (1) O (2) or dication (MB (2+)) and semi-reduced (MB) radicals of the sensitizer and subsequently super-oxide radical (O (2)(-)) are generated. The absence of any effect of SOD and catalase ruled out the DCFH oxidation by O (2)(-), indicating that both (1) O (2) and MB (2+) react with DCFH. Although the formation of DCF was 1 order of magnitude larger in the presence of MB (2+) than in the presence of (1) O (2), considering the rate of spontaneous decays of these species in aqueous solution, we were able to conclude that the reactivity of (1) O (2) with DCFH is actually larger than that of MB (2+). We conclude that DCFH can continue to be used as a probe to monitor general redox misbalance induced in biologic systems by oxidizing radicals and (1) O (2). |
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