Biophotonics of Photosynthesis

Photosynthetic apparatus of Rhodobacter sphaeroides exhibits prolonged charge storage

Photosynthetic proteins have been extensively researched for solar energy harvesting. Though the light-harvesting and charge-separation functions of these proteins have been studied in depth, their potential as charge storage systems has not been investigated to the best of our knowledge. Here, we report prolonged storage of electrical charge in multilayers of photoproteins isolated from Rhodobacter sphaeroides. Direct evidence for charge build-up within protein multilayers upon photoexcitation and external injection is obtained by Kelvin-probe and scanning-capacitance microscopies. Use of these proteins is key to realizing a 'self-charging biophotonic device' that not only harvests light and photo-generates charges but also stores them. In strong correlation with the microscopic evidence, the phenomenon of prolonged charge storage is also observed in primitive power cells constructed from the purple bacterial photoproteins. The proof-of-concept power cells generated a photovoltage as high as 0.45 V, and stored charge effectively for tens of minutes with a capacitance ranging from 0.1 to 0.2 F m^-2.

Linker proteins enable ultrafast excitation energy transfer in the phycobilisome antenna system of Thermosynechococcus vulcanus

Comparison of kinetics of photoexcitation migration from PC620 to APC Core in extracted and intact pentacyclic phycobilisomes ofT. vulcanus. The extracted PBS does not have linker protein, while intact has them and they facilitate the migration.