Photosynthetic Antenna Architecture and its Impact on Energy Transfer

Photosynthesis is the biological process of converting light energy into chemical energy. Photosynthetic organisms utilize this process to sustain life. Cyanobacterial cells contain unique membranes, housing the photosynthetic system, which is composed of many protein complexes. The two key components initiating the process are antenna complexes, called light harvesting complexes (LHC), and reactions centers (RC). Upon light irradiation, light energy is absorbed by the LHCs and immediately transferred to a RC, where the chemical and electron transfer reactions occur. This energy transfer (EET) is highly efficient and relies on an overlap between the energy emitted by the LHC to that absorbed by the RC. The current mechanisms do not fully explain the EET occurring inside and between the complexes. In my research, we wish to investigate this energy transfer in a unique cyanobacteria, A. marina, for which there is a large energetic and physical gap between LHC and RC, yet it remains efficient. In practice, we wish to utilize a unique phenomenon found only in the A. marina membranes, where there is heterogenous separation between domains that contain the main LHC (the Phycobilisome) and domains lacking this complex. These unique domains, that we call LR-islands, contain all the components of the photosynthetic system, which will enable us to isolate it in its entirety from the cells. We use structural, biochemical, spectroscopic, and analytical tools to analyze this unique system. The complete isolated system may present properties typically existing only in vivo, which will help us decipher the full EET mechanism.