Scanning force microscopic studies of Escherichia coli ribosomes on solid substrate surface

Scanning force microscopy (SFM) was used to image ribosomes and ribosomal subunits isolated from Escherichia coli. Topographic images of ribosomal particles adsorbed on a mica surface were obtained directly. At 80 nM, the ribosomes aggregated. At less than or equal to8 nM, a sparser coverage was achieved, with single ribosomes isolated from one another. Although the obtained height was significantly lower than the diameter measured by X-ray diffraction, the height histogram revealed that the observed ribosomal particles belong to three height distributions: approximately 4, 9 and 11 nm. These three distributions correspond to the 70 S ribosome, and the 50 S and 30 S ribosomal subunits, respectively. This work demonstrates that SFM is useful in the discrimination of very small amounts of ribosomal particles on a solid substrate surface.