Dihemic c4-type cytochrome acting as a surrogate electron conduit: Artificially interconnecting a photosystem I supercomplex with electrodes

Connection of photosystem I (PSI) with electrodes has been shown to create artificial photosynthetic systems that hold promise for the synthesis of solar fuels. The high quantum yields of PSI require efficient electron transfer from the electrode to the reaction center of PSI in order to restock the light-induced holes, a task which in nature is performed by small redox proteins. Here, we have investigated the potential "wiring" properties of a dihemic c-type cytochrome (cyt c(4)), in order to efficiently connect PSI with electrodes. Cyt c(4) has shown direct electron transfer (DET) with both hemes in electrical communication with two different electrode materials (ITO and Au) and on the basis of cyt c(4)-multilayer electrodes "self-exchange" properties can also be deduced. Investigation of cyt c(4) in combination with PSI within an inverse opal ITO electrode has shown the dihemic protein to be a valuable molecular electron conduit, able to interconnect the photoenzymatic reaction with the 3D electrode. The properties have been compared with those of electrodes based on monohemic cyt c derived from horse heart.