Solar Hydrogen Production Using Biomimetic Membranes Comprised of Photosynthetic Proteins

It has recently been shown that a molecular wire can successfully tether a hydrogenase enzyme (H₂ase) and a photosynthetic protein complex, Photosystem I (PSI) to integrate hydrogen generation with effective solar energy conversion. The light harvesting component, PSI is a robust membrane-bound protein complex with the ability to provide the chemical potential energy needed to reduce protons.  The H₂ase-PSI construct can generate significant amounts of hydrogen when in solution with an electron donor. Studies to increase hydrogen production rates by the attachment of the H₂ase-PSI construct to an electrode are currently focusing on single particle approaches. In order to achieve maximized electron transfer to immobilized PSI, high protein density and correct orientation on the surface are required. Incorporating PSI in a membrane environment mimics its native state and allows for control over the orientation, which provides favorable conditions for electron transfer. Increasing the stability and orientation of PSI in the membrane can be achieved by using tailored amphiphilic block copolymers (BCPs) as a substitute for native lipids. We have created lipid and polymer membranes with a high density of PSI molecules and characterized the activity using time-resolved optical spectroscopy and photocurrent measurements.