Singlet Oxygen Production by PSII Under Light Stress: Mechanism Detection and the Protective role of β-Carotene

摘要

In this review, I outline the indirect evidence for the formation of singlet oxygen (¹O2) obtained from experiments with the isolated PSII reaction center complex. I also review the methods we used to measure singlet oxygen directly, including luminescence at 1,270 nm, both steady state and time resolved. Other methods we used were histidine-catalyzed molecular oxygen uptake (enabling ¹O2 yield measurements), and dye bleaching and difference absorption spectroscopy to identify where quenchers of ¹O2 can access this toxic species. We also demonstrated the protective behavior of carotenoids bound within Chl–protein complexes which bring about a substantial amount of ¹O2 quenching within the reaction center complex. Finally, I describe how these techniques have been used and expanded in research on photoinhibition and on the role of ¹O2 as a signaling molecule in instigating cellular responses to various stress factors. I also discuss the current views on the role of ¹O2 as a signaling molecule and the distance it might be able to travel within cells.