Figure 19.2.3.1 

Electron diffraction pattern of trehalose-embedded bacteriorhodopsin, with Bragg reflections extending to 2.5 Å. The unit-cell parameter of this 45 Å-thick membrane protein crystal is 62.5 × 62.5 Å arranged in a p3 two-dimensional space group. The raw diffraction pattern was recorded on a Gatan 2k × 2k CCD camera with 300 kV electrons in a JEOL 3000 electron cryomicroscope equipped with a field emission gun and a liquid-helium (4 K) cryoholder. The pattern displayed has been contrast-enhanced using radial background subtraction. A central beam stop was used to prevent saturation of the detector but has blocked off some reflections. for the Friedel-symmetry-related reflections (about 290 pairs) was computed to be about 5%. (Courtesy of Drs Yifan Cheng and Yoshinori Fujiyoshi at Kyoto University.)