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Figure 1
Two-dimensional classification and image selection. (a) Micrograph of a (−17, 5) tube recorded at 2.4 µm underfocus with a Falcon 2 direct-electron detector. (b) Examples of good class averages. (c) Fourier transform of a good class average, showing `pairing layer lines' (arrows) reflecting the dimeric arrangement of receptors on the tube surface lattice (Brisson & Unwin, 1984BB5). The figures in parentheses denote the (h, k; n) indices for major low-resolution layer lines (Toyoshima & Unwin, 1990BB39). Data from class averages where the pairing layer lines [(0, 5; −25) and (1, 3; 2)] were weak or non-existent were omitted from the subsequent image-processing steps.

IUCrJ
Volume 4| Part 4| July 2017| Pages 393-399
ISSN: 2052-2525
https://doi.org/10.1107/S2052252517005243