Translating knowledge of the primary events in photosynthesis to biomimetic systems: Construction of biohybrid antenna and reaction center complexes

Supramolecular membrane complexes are responsible for achieving all major steps of energy conversion, whether they are involved in the capture of light, as in photosynthesis, or in the utilization of redox energy, as in mitochondrial electron transport. How these complexes are structured to carry out their task is the major interest of research in this laboratory. Photosynthetic bacteria areespecially useful subjects for learning more about these processes because these bacteria are able to both capture light energy by a supramolecular complex referred to as the photoreceptor complex (PRC) and to utilize redox energy to drive electron and proton transport.

Our approach to understanding these supramolecular complexes is that of taking the complex apart and putting it back together again. The reconstitution of membrane complexes from their fundamental components allows the systematic probing of structure-function relationships. For example, our laboratory has developed reconstitution methodology for the study of the core light-harvesting complex (LH1) of photosynthetic bacteria and used it to define the specific interactions that hold the complex together and enable its function.

The ability to reconstitute LH1 and its subunit complex (B820) from two small polypeptides and bacteriochlorophyll offers a great opportunity to design and prepare biohybrid systems.  We take advantage of the information encoded in the α and β polypeptides of LH1, honed by evolution, which enables them to be interact with each other and bacteriochlorophyll in vitro to form well-defined oligomeric structures.  By covalently attaching selected chromophores and cofactors to these chemically-synthesized polypeptides, complexes are formed mimicking in vivo systems but with enhanced and selective properties.  Furthermore, it should be possible to form layers of these oligomeric complexes to form a mosaic of mesostructures mimicking the structure of in vivo photosynthetic units.  Monolayers of such mesostructures could be layered onto solid surfaces for potential applications in harvesting solar energy and the construction of specific photoswitches.

Photosynthetic Antenna Research Center (PARC)
Our research is conducted in collaboration with numerous principle investigators of the Photosynthetic Antenna Research Center (PARC), one of the Energy Frontier Research Centers of the Department of Energy.  The center currently has three major themes (1) Natural Antennas: Structure & Efficiency, (2)  Biohybrid Antennas: Organization & Implementation and (3)  Bioinspired Antennas: Design & Characterization.  Our research is focused on themes (2) and (3).