Joachim Reichert, Johannes Barth, Alexander Holleitner (Technische Universitaet Muenchen, Clusters of Excellence MAP and NIM), and Itai Carmeli (Tel Aviv University), proudly present their newly developed method that allows measurements of photocurrents of a single functionalized photosynthetic protein system.
This system can be incorporated in artificial photovoltaic device architectures while preserving their biomolecular functional properties. The proteins consist of a highly efficient single-molecule electron pump, which is driven by light and generates current in electric circuits at a nanoscale.
To achieve these results, the team examined a chlorophyll protein complex contained within the chloroplasts of cyanobacteria. The concept is based on the process of photosynthesis, where light is absorbed and energy is transferred by photosynthetic proteins composed of chlorophyll and carotenoid complexes.
To date, the photocurrents generated by a single protein could not be measured due to insufficient sensitivity of the existing methods. The authors claim that their product “Photosystem-I” has optoelectronic properties comparable only with these found in photosynthetic systems. This, combined with the nanoscale dimensions of the unit, should make it highly desirable for molecular optoelectronic applications.
In order to create electrical contact between molecules in strong optical fields, the scientists used photosynthetic proteins as central elements. These are self-assembles and covalently bound to a gold electrode with cysteine mutation groups.
A gold-covered glass tip was used in a scanning near-field optical microscopy set up to measure the photocurrent. A photon flux optically excites the photosynthetic proteins and provides electrical contact. This is the first time a photocurrent, generated by a single protein, could be measured.