Special specimen preparation methods for image processing in transmission electron microscopy: a review.

One of the important developments in quantitative electron microscopy has been the application of optical and computer imaging methods to electron micrographs. In general these techniques of image analysis have been applied to electron micrographs from isolated biological structures prepared in the presence of various negative stains. To make full use of image processing techniques there are obvious advantages in preparing suitable specimens containing large areas of repeating features. However, the number of naturally occurring biological specimens exhibiting crystalline or paracrystalline features suitable for high resolution electron microscopy and subsequent image analysis is relatively small.Some recent experiments on the in vitro formation of crystalline and paracrystalline arrays from highly concentrated and purified isometric, filamentous and rod-like viruses is reviewed. The problems associated with the preparative procedures for producing two-dimensional and three-dimensional crystalline arrays are discussed together with the possibility of extending the negative staining-carbon film method for studying the gradual dissociation or assembly of viral components.