Low angle x-ray diffraction and biology

The use of the low-angle x-ray diffraction method in biology is described. Some x-ray diffraction patterns have been known since the early 1930's but, in the last decade, many new patterns, which show more reflections than previously, have been recorded. An interpretation of these improved patterns of biological systems provides detailed information on the molecular structure of living cells. The theory and the current status of the low-angle x-ray diffraction method is presented. A brief account of the x-ray studies on collagen, muscle, nerve and membranes is given. Emphasis is given to the history of ideas underlying progress in this area and the current unsolved problems in this field of biophysical research are indicated and discussed.