Fig. 1.

a A 200-mesh grid with a diameter of 3 mm used in this study and its EM images at different magnifications. The middle image shows a square in the mesh. The carbon film on the grid has regular holes of the diameter of 2 μm. The bottom image shows an enlarged view of the holes of the carbon film with a sample. b Schematic illustrations (top) and corresponding EM images (bottom) of holes with thick, good, and thin ice films. In the illustrations, the carbon film and the ice regions are colored gray and blue, respectively, and the solid green and red circles represent native and denatured protein particles, respectively. In each image, the 2-μm-diameter hole at the center of the view is enclosed in a red dashed circle. The region indicated by the black dotted circle within the hole with a thin ice film represents a region from which protein molecules are excluded