Crucial Roles of Electron–Proton Transport Relay in the Photosystem II-Photocatalytic Hybrid System for Overall Water Splitting

Redox shuttle reaction plays a crucial role in electron and proton transfer process of natural and artificial photosynthesis for the solar-to-chemical energy conversion. In nature, photosynthetic electron transfer is delivered efficiently by the elaborated redox cofactors for generation of the reducing equivalents. However, efficient electron/proton transport is still a challenge to couple the natural and artificial photosynthetic system. Herein, we demonstrate a hybrid photosystem in conjugation of plant photosystem II (PSII) and inorganic Ru/SrTiO₃:Rh (Rh-doped) photocatalyst with quinone–ferricyanide relay for overall water splitting reaction under visible light irradiation. Electrons and protons from natural PSII to artificial photocatalyst by a quinone molecule are transported at the bioinorganic interface. Furthermore, the quinone–ferricyanide transport relay is found to be much more efficient in enhancement of the water splitting activity. This work makes it possible to construct the hybrid photosynthetic system by taking the advantages of both natural and artificial systems

Enhancing Cyanobacterial Photosynthetic Carbon Fixation via Quenching Reactive Oxygen Species by Intracellular Gold Nanoparticles

Reactive oxygen species (ROS) play an important role in sensing the redox pressure involved in the electron transfer chains of photosynthesis. However, due to variation in light, ROS accumulation originated from the excess electrons on the acceptor side of photosystem I gives rise to critical inhibition of photosynthetic carbon fixation. How to regulate the extent to which ROS decrease stimulates energy and metabolic fluxes beyond nature must be known to improve CO2 fixation. Herein, we report a strategy to deliver biocompatible gold nanoparticles into cyanobacterium Synechocystis sp. PCC 6803 to dispatch the photosynthetic electron hub for improving CO2 fixation. Biomass of the cyanobacteria increases to 1.6 times with intracellular Au nanoparticles. The enzyme-like gold nanoparticles quench 30% ROS from flavodiiron proteins Flv and increase 21% apparent oxygen evolution, boosting the enzymatic activity of glyceraldehyde 3-phosphate dehydrogenase by an increase of 40% under high light stress. In comparison, gold nanoparticles have no obvious effect on the photosynthetic carbon fixation of the Flv-deficient strain because of severe photoinhibition of photosystems. This intracellular biohybrid strategy for intervention and modulation of complex photosynthetic electron transfer provides new insight into energy conversion and CO2 fixation of photosynthesis