Structure of the E. coli 70S ribosome determined at 100 keV. (a) Typical micrograph after motion correction. Contrast is adjusted to ±3σ from the mean intensity. (b) 2D class averages. (c) Sharpened masked 3D reconstruction of the 70S ribosome from N = 3644 particles without symmetry (C1). (d) Gold-standard FSC plot corresponding to the calculated map, showing the correlation between the phase-randomized (yellow), unmasked (blue) and masked (red) half-maps. The plot terminates at the Nyquist frequency. (e) Orientation distribution of the 70S ribosomes contributing to the final reconstruction (Mollweide projection). The colour scale (linear) corresponds to the normalized density of views (blue, low; red, high). E = 0.7 is the efficiency of the orientation distribution.