(691i) Biomimetic Two-Dimensional Crystals of Photosynthetic Proteins for Membrane Based Energy Production

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 protein orientation, providing favorable conditions for electron transfer. End group modification of lipids is an immobilization technique of bilayers to minimizing the distance between the membrane and surface. PSI will be incorporated with thiolated end group modified lipids and attached to a gold electrode for cathodic photocurrent measurements. Protein incorporation into lipid membranes has been determined by TEM. Results currently show mosaic crystallization of the PSI trimers in unmodified end group lipids.  Increasing the stability, orientation and efficiency of PSI based membranes can be achieved by using tailored amphiphilic block copolymers (BCPs) as a substitute for modified lipids. We have created lipid and polymer membranes with a high density of PSI molecules and have characterized their activity using time-resolved optical spectroscopy and photocurrent measurements.