Crystallographic Image Processing Applications for S-Layers
The three-dimensional structures of many crystalline bacterial surface layers (S-layers) have been studied by electron microscopy. Protein molecules are composed of light elements (mainly C,O,N and H) which give very little contrast and are so sensitive to radiation damage in the electron microscope that it is impossible to observe many details in a protein molecule before it has been destroyed by the electron beam. There are two ways to overcome this dilemma. One is to embed the protein in a staining medium which both increases the contrast and resists radiation damage. The other way is to take micrographs using very low electron doses, before the protein molecules are completely destroyed. Images of hundreds of these “noisy” protein molecules can then be averaged into one image. These two methods can be used individually or in combination with one another.
KeywordsProtein Molecule Protein Monomer Personal Computer Electron Crystallography Swedish Natural Science Research Council
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