47] Optical diffraction and filtering of electron micrographs of contractile proteins

Abstract

Publisher Summary The technique of optical diffraction and its subsequent developments, optical filtering and three-dimensional reconstruction, have found wide use in the analysis of biological structures, particularly the arrays formed by the cytoskeletal and contractile fibrous proteins, such as microtubules z and muscle filaments. This chapter describes the information to be gained from optical diffraction and give some practical hints on how to use a diffractometer once it has been decided that the technique may give valuable information. The optical or Fraunhoffer diffraction pattern is produced when the micrograph is illuminated by a parallel beam of light, which is subsequently focused. The information in the pattern lies in the position, intensity, and relative phase of the regularly disposed diffraction spots. The optical or Fraunhoffer diffraction pattern is produced when the micrograph is illuminated by a parallel beam of light, which is subsequently focused. The information in the pattern lies in the position, intensity, and relative phase of the regularly disposed diffraction spots. Analysis of the data reveals the periodic repeats in the structure, the arrangement of the subunits with respect to one another, and the shape of the subunits. Frequently the results are visualized most clearly in the socalled filtered image of the original micrograph.