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.

Functionally Active Membrane Proteins Incorporated in Mesostructured Silica Films

“…9,58 Despite such beneficial properties of mesostructured oxides, only a few types of membrane proteins, such as the light-harvesting photosynthetic complexes of the bacterium Thermochratium tepidum , have been incorporated in active forms into them, which has generally been achieved by the post-synthetic adsorption of proteins onto powders of these materials. 9,58,59 These approaches, however, lead to particles that often have composition gradients of proteins, small sizes (<10 µm diameters), and low inter-particle connectivities, which limit the usefulness of powders in exploiting the molecular or ion transport properties of membrane proteins over macroscopic length scales.…”

Nanoparticle–Plant Interactions: Two‐Way Traffic

“…SWCNTs also allowed the transmission of signal molecules such as nitric oxide by plants . Noji et al reported that photosynthetic oxygen‐evolving reaction was achieved with a stable activity when a nanomesoporous silica compound was bound to photosystem II (PSII) . The application of nanosilica enhanced the synthesis of chlorophylls and the activity of carbonic anhydrase .…”

Plants emerging with promising nanoworld

“…A nano mesoporous silica compound (SBA) bound with photosystem II increases the activity of photosynthetic oxygen evolving reactions (Noji et al, 2011). It has also been shown that metal nanoparticles can increase the efficiency of chemical energy production in photosynthetic systems (Govorov et al, 2007).…”

“…Also, Noji and co-workers (2011) reported that a nano mesoporous silica compound (SBA) bound with photosystem II (PSII) induced stable activity in a photosynthetic oxygen-evolving reaction, indicating the light-driven electron transport from water to the quinone molecules. The authors suggested that PSII-SBA conjugates might have suitable properties as photosensors and artificial photosynthetic systems (Noji et al, 2011). Recently, Lin and co-workers (2014) developed genetically engineered tobacco plants by replacing the RuBisCO gene with 2 genes encoding the large and small subunits of the Se7942 enzyme form cyanobacterium Synechococcus elongatus (Lin et al, 2014).…”