2007/09/25 by Melih Şener, John D. Olsen, C. Neil Hunter +1 · 1 citation
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · Neuroscience · #Photosynthetic Processes and Mechanisms #Spectroscopy and Quantum Chemical Studies #Photoreceptor and optogenetics research
paper · doi:10.1073/pnas.0706861104
openalex publication_date 2007/09/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/06/24
The photosynthetic unit (PSU) of purple photosynthetic bacteria consists of a network of bacteriochlorophyll-protein complexes that absorb solar energy for eventual conversion to ATP. Because of its remarkable simplicity, the PSU can serve as a prototype for studies of cellular organelles. In the purple bacterium Rhodobacter sphaeroides the PSU forms spherical invaginations of the inner membrane, approximately 70 nm in diameter, composed mostly of light-harvesting complexes, LH1 and LH2, and reaction centers (RCs). Atomic force microscopy studies of the intracytoplasmic membrane have revealed the overall spatial organization of the PSU. In the present study these atomic force microscopy data were used to construct three-dimensional models of an entire membrane vesicle at the atomic level by using the known structure of the LH2 complex and a structural model of the dimeric RC-LH1 complex. Two models depict vesicles consisting of 9 or 18 dimeric RC-LH1 complexes and 144 or 101 LH2 complexes, representing a total of 3,879 or 4,464 bacteriochlorophylls, respectively. The in silico reconstructions permit a detailed description of light absorption and electronic excitation migration, including computation of a 50-ps excitation lifetime and a 95% quantum efficiency for one of the model membranes, and demonstration of excitation sharing within the closely packed RC-LH1 dimer arrays.