title: Singlet oxygen production by PSII under light stress: mechanism, detection and the protective role of β-carotene.
abstract: In this review, I outline the indirect evidence for the formation of singlet oxygen ((1)O(2)) 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 (1)O(2) yield measurements), and dye bleaching and difference absorption spectroscopy to identify where quenchers of (1)O(2) 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 (1)O(2) 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 (1)O(2) as a signaling molecule in instigating cellular responses to various stress factors. I also discuss the current views on the role of (1)O(2) as a signaling molecule and the distance it might be able to travel within cells.
authors.affiliation: Department of Life Sciences, Sir Ernst Chain Building, Imperial College London, London SW7 2AZ, UK a.telfer@imperial.ac.uk.
authors.forename: Alison
authors.initials: A
authors.lastname: Telfer
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport; D004735:Energy Transfer; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism / Q000528:radiation effects; D010788:Photosynthesis / Q000528:radiation effects*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000378:metabolism / Q000528:radiation effects; D010944:Plants / Q000378:metabolism* / Q000528:radiation effects; D011485:Protein Binding; D015398:Signal Transduction; D026082:Singlet Oxygen / Q000032:analysis / Q000378:metabolism*; D013312:Stress, Physiological; D019207:beta Carotene / Q000378:metabolism*
chemical_list: D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D019207:beta Carotene; D002734:Chlorophyll; D026082:Singlet Oxygen
keywords: Chlorophyll; Photosynthesis; Reactive oxygen species; Triplet states