title: Highly efficient photoactivation of Mn-depleted photosystem II by imidazole-liganded manganese complexes.
abstract: The oxygen-evolving complex (OEC) of Mn-depleted photosystem II (PSII) can be reconstituted in the presence of exogenous Mn or a Mn complex under weak illumination, a process called photoactivation. Synthetic Mn complexes could provide a powerful system to analyze the assembly of the OEC. In this work, four mononuclear Mn complexes, [(terpy)2Mn(II)(OOCH3)] x 2 H2O (where terpy is 2,2':6',2''-terpyridine), Mn(II)(bzimpy)2, Mn(II)(bp)2(CH3CH2OH)2 [where bzimpy is 2,6-bis(2-benzimidazol-2-yl)pyridine] and [Mn(III)(HL)(L)(py)(CH3OH)]CH3OH (where py is pyridine) were used in photoactivation experiments. Measurements of the photoreduction of 2,6-dichorophenolindophenol and oxygen evolution demonstrate that photoactivation is more efficient when Mn complexes are used instead of MnCl2 in reconstructed PSII preparations. The most efficient recoveries of oxygen evolution and electron transport activities are obtained from a complex, [Mn(III)(HL)(L)(py)(CH3OH)]CH3OH, that contains both imidazole and phenol groups. Its recovery of the rate of oxygen evolution is as high as 79% even in the absence of the 33-kDa peptide. The imidazole ligands of the Mn complex probably accelerate P680*+ reduction and consequently facilitate the process of photoactivation. Also, the strong intermolecular hydrogen bond probably facilitates interaction with the Mn-depleted PSII via reorganization of the hydrogen-bonding network, and therefore promotes the recovery of oxygen evolution and electron transport activities.
authors.affiliation: State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100080, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.forename: Ping Ping
authors.initials: PP
authors.lastname: Shen
authors.forename: Wei
authors.initials: W
authors.lastname: Shi
authors.forename: Yu Guang
authors.initials: YG
authors.lastname: Song
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Zhou
authors.initials: Z
authors.lastname: Nie
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
mesh_terms: D004579:Electron Transport; D004789:Enzyme Activation; D007093:Imidazoles / Q000737:chemistry*; D008024:Ligands; D008027:Light; D008345:Manganese / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D010777:Photochemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry
chemical_list: D007093:Imidazoles; D008024:Ligands; D009942:Organometallic Compounds; D010455:Peptides; D045332:Photosystem II Protein Complex; D011725:Pyridines; D008345:Manganese; C029899:imidazole; D010100:Oxygen