Functional Interfacing of Rhodospirillum rubrum Chromatophores to a Conducting Support for Capture and Conversion of Solar Energy

Abstract

Owing to the considerable current interest in replacing fossil fuels with solar radiation as a clean, renewable, and secure energy source, light-driven electron transport in natural photosynthetic systems offers a valuable blueprint for conversion of sunlight to useful energy forms. In particular, intracytoplasmic membrane vesicles (chromatophores) from the purple bacterium Rhodospirillum rubrum provide a fully functional and robust photosynthetic apparatus, ideal for biophysical investigations of energy transduction and incorporation into biohybrid photoelectrochemical devices. These vesicular organelles, which arise by invagination of the cytoplasmic membrane, are the sites of the photochemical reaction centers and the light harvesting 1 (LH1) complex. The LH1 protein is responsible for collecting visible and near-IR radiant energy and funneling these excitations to the reaction center for conversion into a transmembrane charge separation. Here, we have investigated the morphology, fluorescence kinetics and photocurrent generation of chromatophores from Rsp. rubrum deposited directly onto gold surfaces in the absence of chemical surface modifications. Atomic force microscopy showed a significant coverage of the gold electrode surface by Rsp. rubrum chromatophores. By in situ fluorescence induction/relaxation measurements, a high retention of the quantum yield of photochemistry was demonstrated in the photoactive films. Chronoamperometric measurements showed that the assembled bioelectrodes were capable of generating sustained photocurrent under white light illumination at 220 mW/cm(2) with a maximum current of 1.5 μA/cm(2), which slowly declines in about 1 week. This study demonstrates the possibility of photoelectrochemical control of robust chromatophore preparations from Rsp. rubrum that paves the way for future incorporation into functional solar cells.

Progress and perspectives in exploiting photosynthetic biomolecules for solar energy harnessing

“…Some biochemical separations from photosystems are also being used, an example of which is the membrane fragments of PS II called PSII particles (BBY-or KM-). 38 Biocomplexes of a higher structural level like chloroplasts 46 and chromatophores 47,48 are also used in biohybrid devices. Apart from utilizing the function of a protein biocomplex in a device, it has also been a well-known approach to use the photosynthetic pigments like chlorophyll and its derivatives in devices like DSSCs.…”

Lipid-Controlled Stabilization of Charge-Separated States (P+QB–) and Photocurrent Generation Activity of a Light-Harvesting–Reaction Center Core Complex (LH1-RC) from Rhodopseudomonas palustris

“…This quantum yield is in good agreement with the value of 0.71 ± 0.01 for chromatophores from Rsp. rubrum S1 (Table , Figure D) and the reported values of 0.74 for the bacterium and 0.63 for the chromatophores . In contrast, when observed in a LDAO micellar system (Figure A), which is a rather harsh surfactant for LH1-RC, F v / F m was quite low, ∼0.5.…”

“…rubrum S1 (Table 1, Figure 3D) and the reported values of 0.74 for the bacterium 44 and 0.63 for the chromatophores. 52 In contrast, when observed in a LDAO micellar system (Figure 3A), which is a rather harsh surfactant for LH1-RC, 53 F v /F m was quite low, ∼0.5. After this fluorometric experiment was performed at room temperature, B875 appeared to be bleached.…”

Demonstration of asymmetric electron conduction in pseudosymmetrical photosynthetic reaction centre proteins in an electrical circuit

“…It is well established that purple bacterial RCs can be interfaced with conducting electrodes for the generation of photocurrents and much is known about suitable combinations of electrode materials, linkers and redox mediators, but relatively little is known about the actual mechanism through which photocurrents are generated. Most of what has been concluded in recent years has been based on indirect evidence such as the relative redox or vacuum potentials of different components in a particular electrochemical cell, the direction of current flow under different potentials applied to the working electrode, the requirement for specific types of redox mediator and the action of a limited number of available inhibitors 12 13 14 15 16 17 47 48 49 50 51 52 53 .…”