Effect of surface roughness of carbon support films on high- resolution electron diffraction of two-dimensional protein crystals

The surface roughness of carbon films, which are used as a specimen support in high-resolution electron microscopy, has been investigated by atomic force microscopy. Carbon films were prepared by evaporating carbon onto mica. We found that the carbon surface that had been in contact with the mica was between 3 and 9 times smoother than the surface which had faced the carbon source. Surfaces of carbon films prepared by multiple evaporation were smoother than films evaporated in a single step. The surface roughness on the mica side of these films was close to that of mica. Two-dimensional crystals of plant light-harvesting complex yielded isotropically sharp high-resolution electron diffraction patterns at high tilt angles only when supported on the smoothest carbon films, produced by multiple evaporation.