Photosystem II electron transport rerouted by single-walled carbon nanotubes

The development of various biohybrid natural or artificial systems to enhance solar energy conversion is a high priority in contemporary energy research. The fusion of highly dynamic and adaptive photosynthetic structures with easily manipulated inorganic materials at nanoscale could open new opportunities for the development of solar-powered biotechnology for renewable energy production. In this context, the distinct photochemical and electrochemical properties of single-walled carbon nanotubes (CNTs) have stimulated research interest in nanomaterial utilization in various in vivo and in vitro photosynthetic biohybrid setups. The mechanism of interaction between the nanotubes and photosynthetic structures is still unclear. The limited number of studies on the interplay between CNTs and photosynthetic complexes provides controversial indications of the energy flow within the biohybrid system. Our studies on in vivo effects of nanotubes on photochemical reactions of green alga Chlamydomonas reinhardtii indicate that the CNTs can alter the electron transport of Photosystem II and may facilitate the non-radiative loss of excitation energy. To gain further insight into these processes, we analyzed the electro-optical interactions of CNTs with isolated photosynthetic structures of varying complexity. Analyzing the possible pathways of energy decay in the model systems studied, our results indicate a possible leakage of photosynthetic electrons toward the nanotubes, most likely at the level of the Photosystem II acceptor site.