Electron crystallography of macromolecules.

Numerous technical advances in electron crystallography have facilitated determination of the three-dimensional structures of macromolecules, especially those that form two-dimensional or helical periodic arrays. Several recent studies have demonstrated the utility of this technique for visualizing secondary structure such as alpha-helices and beta-sheets of membrane proteins and, in one case, the entire polypeptide backbone. Electron crystallography, therefore, has great potential as a tool for studying structural problems that are relevant to both molecular biology and biotechnology.