Single molecule studies on purple bacterial antenna complexes

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Photosynthesis begins with the absorption of solar energy by antenna pigments. This absorbed energy is then rapidly and efficiently transferred to reaction centres where it is trapped and used to drive photosynthesis. Light-harvesting is therefore and essential and fundamental part of this very important biological process that ultimately provides all the food we eat, the oxygen we breathe and cleans the air by removing carbon dioxide. This proposal aims to use a combination of X-ray crystallography and single molecule spectroscopy to study both the physical and electronic structure of a group on light-harvesting antenna complexes obtained from purple photosynthetic bacteria. These bacteria have proved to be excellent model systems in which to study the fundamental reactions going on in the earliest reaction of photosynthesis. Normal spectroscopy looks at the properties of large populations of molecules, so-called ensemble spectroscopies. However because this averages over all the molecules present and because each molecule is not identical many important details are averaged out and lost. Looking at individual molecules allows these details to be observed and they are, in this case with the antenna complexes, essential if we wish to understand how antenna complexes function. In this regard single molecule spectroscopy is a uniquely important tool.