Fundamental and applied studies of biological light-harvesting systems

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My research centres on microbes that capture solar light and convert its energy to electrical current, using special proteins and pigments combined in a biological photosystem or photosynthetic reaction centre (RC). My approach ranges from finding new species to engineering proteins with new biophysical properties, and applications in biophotovoltaic devices that convert sunlight to electricity. Canada is committed to reducing carbon emissions (www.ec.gc.ca) and of the non-nuclear, carbon-neutral electrical energy sources (solar, wind, biomass, water) solar has the greatest potential (order of 10-fold greater than the other three combined). The use of biological photosystems in photovoltaics has become possible due to our improved knowledge of these systems and new gene engineering methods, but we still need to answer many questions about the design and creation of photon and electrical circuits in proteins, to make full use of the potential of these systems. The proposed research has two Aims: 1) to discover and characterize biological photosystems with new properties, using natural samples; 2) to create novel electrical pathways into, out of, and through proteins that are part of an electrical circuit, using synthetic biology. Each aim will benefit from new information generated in the other. 1. To get natural samples we will: i) cultivate new species from natural environments; ii) extract genes from metagenome (genetic material collected from the environment) archives. We will use the genes we get to create active photosystems in our synthetic biology system, based on the photosynthetic bacterium Rhodobacter sphaeroides, which grows at moderate temperatures (20-45 C). Photosystems that have new physicochemical properties will be used to design biophotovoltaic devices. The goal is to use genes from thermophilic (heat loving) bacteria as their proteins should tolerate high temperatures (50-70 C) that might occur in solar energy applications such as on rooftops. 2. We will begin creating new electrical pathways with the RC of R. sphaeroides, both alone and as a co-complex encircled by a light-harvesting pigment-protein complex, which in some cases provides heat tolerance. We will change amino acids at specific sites in the protein to block the natural electron transfer pathway, and to divert high-voltage electricity from the RC to an electrode connected to a circuit. We will test if tryptophan and tyrosine residues may be used to create novel electron-tunnelling pathways between excited photopigments and an external electrical circuit. The initial goal is to create new pathways that extract electrical current of increased voltage using R. sphaeroides proteins. Later work will be on photosystems from thermophilic bacteria found in Aim 1. Our work will create new knowledge, advance photovoltaic technology, and train students for future careers in research and technology development.