TEACHING ELECTRON-DIFFRACTION AND IMAGING OF MACROMOLECULES

Electron microscopic analysis can be used to determine the three-dimen sional structures of macromolecules at resolutions ranging between 3 a nd 30 angstrom. It differs from nuclear magnetic resonance spectroscop y or x-ray crystallography in that it allows an object's Coulomb poten tial functions to be determined directly from images and can be used t o study relatively complex macromolecular assemblies in a crystalline or noncrystalline state. Electron imaging already has provided valuabl e structural information about various biological systems, including m embrane proteins, protein-nucleic acid complexes, contractile and moti le protein assemblies, viruses, and transport complexes for ions or ma cromolecules. This article, organized as a series of lectures, present s the biophysical principles of three-dimensional analysis of objects possessing different symmetries.