Three-dimensional reconstruction of the 30S E. coli ribosomal subunit

Various models of the 30S subunit have been proposed based on visual evaluation of electron micrographs. Recently, however, techniques have been developed which facilitate the evaluation of non-homogeneous populations of molecular images. Aligned images of macromolecules are thereby submitte to multivariate statistical analysis in the form of Correspondence Analysis (CA). Classes can be determined within the population of images with th aid of various automatic classification schemes. A pilot study indicated that these classes— as was expected— correlate highly to a particu lar (rotation) position of the molecules in the electron microscopical prepa ration. If we are, by some means, capable of assigning absolute angles to each projection class, a three-dimensional reconstruction of the 30S subunit becomes feasible. A first step towwards this goal is the "seriation" of the projection classes into their logical order: "the logical circle in hyperspace". For the analysis a population of 422 molecular images was selec ted including the 101 molecules used for the pilot study.