Plots of the Euler angle distribution of RyR2 particle orientations on regular holey EM grids (A) and on deformed EM grids (B), particles (3,756 particles from regular grids, and 3,573 from deformed grids) are from images that were collected without tilting the specimen grids in the microscope. Since the RyR2 is a homo-tetramer, 4-fold symmetry is usually applied during image processing, and so the Euler angle distribution only covers one quarter of the 3D sphere. The diameters of the circles indicate the relative numbers of particles. More particles are distributed toward high Euler angles (≥ 30°) in the deformed grids than in the regular EM grids.