HIGH-RESOLUTION SHADOWING OF FREEZE-DRIED BACTERIAL PHOTOSYNTHETIC MEMBRANES - MULTIVARIATE STATISTICAL-ANALYSIS AND SURFACE RELIEF RECONSTRUCTION

The surface reliefs of photosynthetic membranes from the bacterium Ectothiorhodospira halochloris have been reconstructed from shadowing data. Freeze-dried membranes were shadowed unidirectionally with tantalum/tungsten at low specimen temperature (approx. 20 K). The membranes, which contain the photosynthetic complexes hexagonally packed, show two distinctly different faces. Analysis of the apparent molecular displacements on the two faces suggests that not all features are compatible with P6 symmetry but may vary from one unit cell to another. Correspondence analysis and differential averaging created subsets reflecting the nature of the variability, namely an asymmetry and rotational variability of the reaction center complex with respect to the surrounding ring of high-harvesting complexes.