Spatially filtered images of B. subtilis alpha-amylase crystals.

Microcrystals of B. subtilis alpha-amylase have been negatively stained and examined by electron microscopy. The micrographs were then subjected to spatial filtering and averaging using a Fourier transform procedure programmed for a mini computer. From these 'enhanced' images refined crystallographic parameters were obtained and a model for the packing of the asymmetric units within the crystal was derived. In addition, these parameters obtained from electron microscopy are compared with those derived from limited X-ray diffraction data on macrocrystals of the same form.