title: Singlet oxygen formation and chlorophyll a triplet excited state deactivation in the cytochrome b6f complex from Bryopsis corticulans.
abstract: We have attempted to investigate the correlation between the detergent-perturbed structural integrity of the Cyt b (6) f complex from the marine green alga Bryopsis corticulans and its photo-protective properties, for which the nonionic detergents n-octyl-beta-D-glucopyranoside (beta-OG) and n-dodecyl-beta-D-maltoside (beta-DM), respectively, were used for the preparation of Cyt b (6) f, and the singlet oxygen ((1)O(2)*) production as well as the triplet excited-state chlorophyll a ((3)Chl a*) formation and deactivation were examined by spectroscopic means. Near-infrared luminescence of (1)O(2)* (approximately 1,270 nm) on photo-irradiation was detected for the beta-OG preparation where the complex is mainly in oligomeric state, but not for the beta-DM one in which the complex exists in dimeric form. Under anaerobic condition, photo-excitation of Chl a in the beta-DM preparation generated (3)Chl a* with a lower quantum yield of Phi(T) approximately 0.02 and a longer lifetime of approximately 600 micros with respect to those as in the case of beta-OG preparation, Phi(T) approximately 0.12 and 200-300 micros. These results prove that the enzymatically active and intact Cyt b (6) f complex on photo-excitation tends to produce little (3)Chl a* or (1)O(2)*, which implies that the pigment-protein assembly of Cyt b (6) f complex per se is crucial for photo-protection.
authors.affiliation: Beijing National Laboratory for Molecular Science, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Ma
authors.forename: Xiao-Bo
authors.initials: XB
authors.lastname: Chen
authors.forename: Min
authors.initials: M
authors.lastname: Sang
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Zhang
authors.forename: Liang-Bi
authors.initials: LB
authors.lastname: Li
authors.forename: Ting-Yun
authors.initials: TY
authors.lastname: Kuang