x-ray diffraction analysis

A technique used to determine the three-dimensional pattern of large molecules such as proteins or DNA. A beam of x-rays is fired at a crystal and the resulting diffraction pattern is recorded on a photographic plate behind the crystal. The crystal is rotated slightly and is subjected to more x-rays. By repeating this, the three-dimensional pattern can be determined. It was work of this nature that showed DNA to be a regular double helix.