Development of Novel Apparatus for Singlet Oxygen Detection and Its Application as Biological Tool

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Singlet oxygen, a highy reacive and toxic intermediate, plays an important role in many photochemical and photobiological processes and has been postulated to be a major species mediating photochemical action in biological systems. Many attempts have been made to find evidence of singlet oxygen generation in various photosensitized reactions and enzymatic systems. Compared with the known nonspecific techniques for the detection of singlet oxygen, direct obervation of the emission at 1268 nm has proven to be the most reliable approach for singlet oxygen detection. We have constructed a sensitive near-infrared emission spectrometer with germanium detector, which scans from 1000 nm to 1600 nm. We applied this apparatus for detection of singlet oxygen produced by laser-excited photosensitive dyes. For example, the data about new quinolones will be shown below.New quinolones have potent anti-bacterial activity based on the inhibition of bacterial DNA gyrase and have been widely used as a cu … More rative medicine. However, some of them have been reported to induce photodermatosis as side effect. We have examined 1)the production of reactive oxygen species (ROS) mediated by new quinolones shown below and 2)participation of ROS in the phototoxicity. We employed the near-infrared (1268 nm) emission spectrometer to detect singlet oxygen specific emission, and NBT reduction method to detect superoxide. We compared ROS formation ability of the new quinolones quantitatively. Since it is known that new quinolones are able to interact with DNA,we also investigated the photodynamic DNA strand breaking activity that can estimate the phototoxicity of the new quinolones. All the new quinolones investigated in this study were found to produce singlet oxygen, and they also produced superoxide except SPFX.It has been little reported that colorless or pale color compounds act as photosensitizer that produces ROS.They also had photodynamic DNA strand breaking activity. The main active species was probably singlet oxygen, because NaN,inhibited the activity strongly. Less