Stahlberg H Dubochet J Vogel H Ghosh R 1998 The basic photosynthetic unit containing the reaction centre and the light-harvesting I complex (RC-LHI) of the purple non-sulphur bacterium Rhodospirillum rubrum was purified and reconstituted into two-dimensional (2D) membrane crystals. Transmission electron microscopy using conventional techniques and cryoelectron microscopy of the purified single particles and of 2D crystals yielded a projection of the RC-LHI complex at a resolution of at least 1.6 nm. In this projection the LHI ring appears to have a square symmetry and packs in a square crystal lattice. The square geometry of the LHI ring was observed also in images of single isolated particles of the RC-LHI complex. However, although the LHI units are packed identically within the crystal lattice, a new rotational analysis developed here showed that the reaction centres take up one of four possible orientations within the ring. This fourfold disorder supports our interpretation of a square ring symmetry and suggests that a hitherto undetected component may be present within the photosynthetic unit. https://sonar.ch/global/documents/277760 eng info:eu-repo/semantics/altIdentifier/doi/10.1006/jmbi.1998.1975 info:eu-repo/semantics/altIdentifier/pmid/9743629 Journal of molecular biology. - 1998 Bacterial Chromatophores Bacterial Proteins Cryoelectron Microscopy Crystallization Hydrogen-Ion Concentration Light-Harvesting Protein Complexes Microdialysis Microscopy, Electron Molecular Weight Phospholipid Ethers Photosynthetic Reaction Center Complex Proteins Protein Conformation Rhodospirillum rubrum Solubility Spectrum Analysis Are the light-harvesting I complexes from Rhodospirillum rubrum arranged around the reaction centre in a square geometry? http://purl.org/coar/resource_type/c_6501