Chapter 22: Reactions of Singlet Oxygen with Organic Devices

Singlet molecular oxygen (¹O₂) is a reactive oxygen species that is typically generated by photodynamic action, but may also arise via disproportionation of lipid peroxyl radicals or as a low-yield product of certain enzymatic reactions, e.g. eosinophil peroxidases. This chapter provides a broad review of (i) how ¹O₂ reacts with unsaturated lipids in biomembranes, leading to membrane-damaging lipid peroxidation that can be exacerbated by iron and reductants; (ii) types of lipid hydroperoxides (LOOHs) generated by ¹O₂ attack and how some cholesterol-derived species (ChOOHs) qualify as reliable and convenient mechanistic reporters for distinguishing between ¹O₂ and free-radical attack; (iii) cutting-edge analytical approaches for ¹O₂-generated LOOHs; (iv) possible fates of these LOOHs, including one-electron vs. two-electron reduction, and spontaneous vs. protein-facilitated intermembrane translocation; and (v) unique features of LOOHs as potential redox-signaling molecules. Finally, some prospects for future developments in this area will be discussed.