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There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
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Photosynthesis is one of the great-impact inventions of biological evolution. Indeed, life on Earth is fueled energy-wise mainly by sun light. Many, so-called photosynthetic, life forms harvest sun light directly, for example, plants, algae and bacteria; other life forms use sun light indirectly, like herbivorous animals. This lecture tells the story a particular simple, yet amazing photosynthetic apparatus, the chromatophore, found in purple bacteria.
The photosynthetic chromatophore is a spherical shell of 50 nm diameter that exists in hundreds of copies in the bacterial cell and converts sun light into chemical synthesis of an energy-rich molecule, adenosin triphosphate (ATP). Each chromatophore is made of over hundred protein complexes with thousands of light absorbing and electron conducting molecules embedded in them; the complexes are held together by a membrane made of 20,000 lipid molecules. Despite its complexity and heterogeneity the chromatophore can be viewed today through advances in experimental and computational biology at atomic- and electronic-level detail in its entire structure and function. One sees a clockwork of linked, mostly rather elementary processes: light absorption, coherent and incoherent exciton formation, intermolecular electron and proton transfer, charge carrier diffusion, electrostatic steering of protein- mediated electron conduction, molecular motor action driven by proton conduction, and lastly mechanically driven ATP synthesis.
For the first time a major part of a biological cell has been resolved in its entirety at the level of truly basic physics, showcasing how Angstrom- scale processes lead to 100-nm-scale intelligent overall function. In viewing the chromatophore through a beautifully detailed movie one can recognize in an exemplary fashion how evolution engineered an apparatus crucial for solar energy-driven life on Earth, utilizing amazing processes on the small scale by linking them together in a clock-work fashion such that an efficient, robust and adaptive cell-scale function emerges.
