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- Materials and Methods
Photoexcitation to generate triplet state has been proved to be the main photoreaction in homogeneous system for many benzoquinone derivatives, including oxidized coenzyme Q (CoQ) and its analogs. In the present study, microemulsion of CoQ, a heterogeneous system, is employed to mimic the distribution of CoQ in biomembrane. The photochemistry of CoQ10 in microemulsion and cyclohexane is investigated and compared using laser flash photolysis and results show that CoQ10 undergoes photoionization via a monophotonic process to generate radical cation of CoQ10 in microemulsion and photoexcitation to generate excited triplet state in cyclohexane. Meanwhile, photoreactions of duroquinone (DQ) and CoQ0 in microemulsion are also investigated to analyze the influence of molecular structure on the photochemistry of benzoquinone derivatives in microemulsion. Results suggest that photoexcitation, which is followed by excited state-involved hydrogen-abstraction reaction, is the main photoreaction for DQ and CoQ0 in microemulsion. However, photoexcited CoQ0 also leads to the formation of hydrated electrons. The isoprenoid side chain-involved high resonance stabilization is proposed to explain the difference in photoreactions of CoQ0 and CoQ10 in microemulsion. Considering that microemulsion is close to biomembrane system, its photoionization in microemulsion may be helpful to understand the real photochemistry of biological quinones in biomembrane system.