The high quantum efficiency of photosynthetic reaction centers (RCs) makes them attractive for bioelectronic and biophotovoltaic applications. However, much of the native RC efficiency is lost in communication between surface-bound RCs and electrode materials. The state-of-the-art biophotoelectrodes utilizing cytochrome c (cyt c) as a biological wiring agent have at best approached 32% retained RC quantum efficiency. However, bottlenecks in cyt c-mediated electron transfer have not yet been fully elucidated. In this work, protein film voltammetry in conjunction with photoelectrochemistry is used to show that cyt c acts as an electron-funneling antennae that shuttle electrons from a functionalized rough silver electrode to surface-immobilized RCs. The arrangement of the two proteins on the electrode surface is characterized, revealing that RCs attached directly to the electrode via hydrophobic interactions and that a film of six cyt c per RC electrostatically bound to the electrode. We show that the additional electrical connectivity within a film of cyt c improves the high turnover demands of surface-bound RCs. This results in larger photocurrent onset potentials, positively shifted half-wave reduction potentials, and higher photocurrent densities reaching 100 μA cm–2. These findings are fundamental for the optimization of bioelectronics that utilize the ubiquitous cyt c redox proteins as biological wires to exploit electrode-bound enzymes.
- biosolar cells
- cytochrome c
- reaction center
Friebe, V. M., Millo, D., Swainsbury, D. J. K., Jones, M. R., & Frese, R. N. (2017). Cytochrome c Provides an Electron-Funneling Antenna for Efficient Photocurrent Generation in a Reaction Center Biophotocathode. ACS Applied Materials and Interfaces, 9(28), 23379-23388. https://doi.org/10.1021/acsami.7b03278