MIMICKING THE PHOTOSYNTHETIC ENERGY CONVERSION IN ARTIFICIAL PROTEOLIPOSOMES

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Nature's photosynthetic energy conversion has operated for few billions of years and made life possible on our planet. The enzymes that carry out the light dependent reactions operate with very high efficiencies and if their function is understood properly they can inspire to develop artificial solar energy converters. The aim of the proposed research project is to contribute toward the understanding how the light-induced redox reactions are coupled to proton translocation leading to the energization of the biological membrane. We focus our attention to the pathways of the protons across the membrane and the construction of a biomimetic system that reduces the complicated natural mechanism to its basic elements. We aim to design and construct a photocycle that pumps protons from the interior to the exterior of the liposome upon illumination with an efficiency comparable to the native system. The reaction center protein from purple photosynthetic bacteria will be utilized to absorb the light energy and convert it to a charge separated state. The second enzyme that complements the proton pumping in Nature (cytochrome bc1 complex) will be substituted with systematically selected redox centers to complete the cycle. This simplified system will allow us to study the regulatory effect of the transmembrane pH gradient on the reaction kinetics of the overall electron transfer and to explore alternative mechanisms of charge stabilization in conditions that resemble the natural environment of the reaction center protein. By studying the optimal construction of a simple photochemical cell based on photosynthetic proteins and redox cofactors embedded in artificial membranes a recipe can be offered how solar energy can be converted into chemical potential under laboratory conditions using bioinspired nanosystems. From this aspect the planned research may have impact on both basic and applied sciences keeping a faint chance of economic utilization on the horizon.