Self-assembling photosynthetic reaction centers on electrodes for current generation

Area of Science:

• Biophysics
• Renewable Energy
• Materials Science

Background:

• Photosynthetic reaction centers (RCs) facilitate light-induced charge separation, making them promising for solar energy applications.
• Efficient immobilization of intact RCs on electrode surfaces is crucial for developing functional devices.

Purpose of the Study:

• To present a straightforward immobilization system for intact RCs from Rhodobacter sphaeroides on an electrode.
• To characterize the binding properties and orientation of immobilized RCs.
• To assess the stability and detachment of the immobilized RCs.

Main Methods:

• Utilized a hexameric histidine tag on the H subunit (HHisRC) for nickel ligand binding to a nickel-nitrilotriacetic acid (Ni-NTA) chip.
• Measured binding constants using surface plasmon resonance (SPR).
• Immobilized HHisRCs on an indium tin oxide electrode with an Ni-NTA gold substrate and analyzed photoinduced displacement current and detachability.

Main Results:

• Achieved a high binding constant (1.6 x 10^8 M^-1) for HHisRC to the Ni-NTA chip.
• Determined that the H subunit side of HHisRC faces the electrode surface based on photoinduced displacement current.
• Demonstrated successful detachment of HHisRC using an imidazole solution wash, leading to the disappearance of photoinduced current.

Conclusions:

• Developed a simple and effective immobilization strategy for RCs using nickel-histidine tag binding.
• The immobilization system allows for controlled orientation and reversible attachment of RCs to electrodes.
• This method holds potential for creating reproducible photocurrent devices for solar energy conversion.