Electron cryo-microscopy of macromolecular assembly at 400 kV

Abstract

Electron cryo-microscopy has proven to be a valuable technique for determining 3-dimensional structures of biological macromolecules. The cryo technique is capable of preserving biological specimens in their native conformation and of reducing radiation damage during the microscopic observation. Computer processing is used to combine data from different angular views for 3-dimensional reconstruction. The structural detail revealed in this type of analysis can be limited by the quality of the electron microscopic images and the computational procedures used to retrieve the low contrast signals. So far, the highest resolution study of electron cryo-microscopy is bacteriorhodopsin where the polypeptide chain can be traced and some of the amino acid side chains can be identified. Though high resolution structure can be obtained by electron crystallographic analysis, further improvement can be made in several areas. These include specimen flatness, specimen movement induced by the electrons, and achievement of better signal to noise ratios in the images.