Fig. 2.

Electron microscopy analyses of Bri2 BRICHOS oligomers. a Transmission electron micrograph of negatively stained Bri2 BRICHOS oligomers recorded with a JEOL JEM2100F electron microscope and a DE-20 direct electron detector. b Representative 2D-classes of Bri2 oligomers. The class averages are consistent with an approximate 2-fold symmetry. The yellow frames indicate the most obvious 2-fold views. The side of each box side is approximately 22 nm. c 3D density map of Bri2 BRICHOS oligomer with dihedral (D2) symmetry. The viewing directions are parallel to the three different 2-fold axes. The map was based on 2718 particles extracted from images recorded on a DE-20 detector. The voxel size of the map is 2.076 Å. d The Fourier shell correlation (FSC) curve between reconstructions was produced by splitting the data set in two halves. Both halves were reconstructed separately. The resolution of ~17 Å for the reconstructed 3D density map was calculated from the curve at FSC = 0.143 (dotted lines)