Juha M. Linnanto
University of Tartu, Estonia
Title: Energy transfer in the photosynthetic unit of green sulphur bacterium
Biography
Biography: Juha M. Linnanto
Abstract
Statement of the problem: Photosynthesis is the most important biological energy conservation pathway on the Earth, and oxygenic photosynthesis produces most of the oxygen we breathe. Photosynthetic organisms make use of solar energy to create free chemical energy that is used in their metabolic reactions. For light energy to be store by photosynthesis, it must first be absorbed by pigment molecules associated with the photosynthetic apparatus. The Light-Harvesting (LH) antenna systems collect sunlight and transfer excitation energy rapidly to the photosynthetic Reaction Centers (RCs), where the energy is trapped in an electron-transfer reaction. Photosynthetic Units (PSUs) of phototrophic organisms have such structural architecture that light energy absorbed by an LH antenna is transferred to a RC through efficient Energy Transfer (ET). To investigate these processes both experimental and theoretical methods are needed. There are available only a few experimentally solved atomic-resolution X-ray LH and RC structures. Thus, different computational methods together with experimental structural and spectroscopic information are needed to generate three-dimensional pigment-protein LH antenna model structures. The purpose of this study is to generate atomistic model for the PSU of Green Sulphur Bacteria (GSB) and to explain solar energy transfer processes in this system. Experimental X-ray, electron microscopy, and cryo-electron microscopy LH and RC structures of GSB are used as initial structure models in this study. The PSU of GSB is very interesting system because it contains both self-aggregated pigment oligomer LH complexes as also pigment-protein LH complexes. All of these complexes have their own specific absorption spectrum and energy levels. The PSU of the GSB allows some of GSB to live in extraordinarily low light conditions under which no other photosynthetic organisms can grow, such as in the bottom of stratified lakes, deep in the sea and near geothermal vents.