title: Photosynthetic oxygen evolution in mesoporous silica material: adsorption of photosystem II reaction center complex into 23 nm nanopores in SBA.
abstract: An oxygen-evolving photosynthetic reaction center complex (PSII) was adsorbed into nanopores in SBA, a mesoporous silica compound. We purified the dimer of PSII complex from a thermophilic cyanobacterium, Thermosynechococcus vulcanus, which grows optimally at 57 °C. The thermally stable PSII dimeric complex has a diameter of 20 nm and a molecular mass of 756 kDa and binds more than 60 chlorophylls. The SBA particles, with average internal pore diameters of 15 nm (SBA(15)) and 23 nm (SBA(23)), adsorbed 4.7 and 15 mg of PSII/g SBA, respectively. Measurement with a confocal laser-scanning microscope indicated the adsorption of PSII to the surface and the inner space of the SBA(23) particles, indicating the adsorption of PSII into the 23 nm silica nanopores. PSII did not bind to the inner pores of SBA(15). PSII bound to SBA(23) showed the high and stable activity of a photosynthetic oxygen-evolving reaction, indicating the light-driven electron transport from water to the quinone molecules added in the outer medium. The PSII-SBA conjugate can be a new material for photosensors and artificial photosynthetic systems.
authors.affiliation: Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku Nagoya, Aichi 464-8602, Japan.
authors.forename: Tomoyasu
authors.initials: T
authors.lastname: Noji
authors.forename: Chihiro
authors.initials: C
authors.lastname: Kamidaki
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kawakami
authors.forename: Jian-Ren
authors.initials: JR
authors.lastname: Shen
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kajino
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Fukushima
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sekitoh
authors.forename: Shigeru
authors.initials: S
authors.lastname: Itoh
mesh_terms: D000327:Adsorption; D000818:Animals; D002417:Cattle; D053758:Nanoparticles / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D010316:Particle Size; D010777:Photochemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D016062:Porosity; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D045332:Photosystem II Protein Complex; D012710:Serum Albumin, Bovine; D012822:Silicon Dioxide; D010100:Oxygen