Harrold Jr., John W.. Assembly of natural photosynthetic components on graphene oxide and gold surfaces for light energy transduction. Retrieved from https://doi.org/doi:10.7282/T3C53JBG
DescriptionPhotosynthetic reaction centers are integral membrane proteins of particular interest for their remarkable ability to catalyze photo-induced charge separation with high quantum efficiency. For this reason they have been targeted for integration in biohybrid systems for capture and conversion of solar energy. In this study isolated photosynthetic core complexes from phototrophic organisms are interfaced with conductive materials for the development of photoelectrochemical systems. Photosystem II core complexes (PSII CCs) bearing poly histidine tags isolated from genetically modified Thermosynechococcus elongatus, were tethered to a graphene oxide (GO) support through immobilized metal coordination sites. The PSII CCs tethered to GO-coated gold electrodes and GO nanosheets in suspension showed 59% retention of quantum yield of photochemistry. Fluorescence kinetic relaxation analyses indicates that a direct electron transfer occurs between embedded quinone (QA) of PSII and GO. Flash oxygen evolution activity shows a threefold improvement in comparison with isolate PSII in suspension. Photosystem I core complexes (PSI CCs) isolated from Synnehcoccous PCC 7002 was also immobilized on GO. The co-immobilization of PSII and PSI on GO resulted in a biohybrid electron transport chain on the model of the photosynthetic Z-scheme. As a robust alternative to PSII, a very labile enzyme, chromatophores isolated from the bacterium Rhodospirillum rubrum were adsorbed on gold electrodes. These intracytoplasmic membrane vesicles containing bacterial type II reaction centers yielded a maximum photo-driven current of 1.5 μA/cm2 that slowly declined in a week. This study demonstrates the utility of bottom-up reconstruction of biological nanostructure as a platform for fundamental experimental approaches and the pursuit of new paradigms toward renewable energy resources.