Organized Light Harvesting Photosystem I Layers on a Cytochrome C for the Construction of New Photobioelectrodes

Artificial approaches to mimick natural photosynthesis are an emerging field of research with impact on photobiocatalytic systems and photobiovoltaic applications. Herein, we manage the assembly of two heterologous proteins exhibiting key features for the usage in biohybrid light-converting electrode systems. We combine the photon converting pigment-protein super-complex - photosystem I (PSI), from natural photosynthesis of cyanobacteria¹ - with a small electron carrier, cytochrome c (cyt c) from the respiratory chain, in mono- and multilayer arrangements. Often, PSI has a random orientation when self-assembled on surfaces and provides a slow direct electron transfer (DET).² Our strategy to overcome these issues, is to assemble PSI with the help of electron carriers similar to native electron transport. This provides two advantages: (1) redox protein mediated indirect electron transfer (IET) may yield high photocurrents, due to rather small electron tunneling distances; (2) redox proteins can be considered as an assembly template on which PSI can adsorb efficiently by reason of electrostatic and/or native affinity, which has been studied by surface plasmon resonance (SPR). By this approach, we developed photoreactive protein layers on electrodes, which have a potential-driven cathodic photocurrent to reduce the PSI after light induced electron-hole-pair separation. The study determines the role of cyt c in such organised films, which works as a template but also show the ability to connect and wire the PSI with the electrode.³ This is also valid in a multilayer arrangement with PSI far away from the electrode surface. The system can be seen as a network with electron conducting elements forming a protein 3D architecture. In order to increase the photocurrent of such electrodes, a multilayer approach and a time-dependend self-growth of cyt c/PSI-architectures was developed. The presented work can be considered as a contribution to current research in order to develop organised protein films for the effective conversion of light into electrical and/or chemical energy.

(1) Grotjohann, I.; Fromme, P. Photosynth. Res. 2005, 85 (1), 51−72.

(2) Ciesielski, P. N. et al. J. Phys. Chem. A 115, 3326–34 (2011).

(3) Stieger, K. R.; Feifel, S. C. et al. Phys. Chem. Chem. Phys. 16, 15667-15674 (2014).