X-ray crystallography was first developed as a means of determining the nature of X-rays themselves. It was not intended to be a research tool. In crystallography X-rays are used to probe the structures of crystals. The pattern of diffracted X-rays is similar to an atomic "shadow." By examining where the X-rays are blocked by the crystal's atoms, scientists can define the structure of those atoms.
Medical Uses for Crystallography
Perhaps the most important application of X-ray crystallography is its use in synthesizing (blending) substances. Many of the medicinal chemicals that have been discovered by scientists are very difficult to produce naturally in large amounts. When this happens, it becomes necessary to create the chemicals in the laboratory through synthesis. Before a chemist can synthesize a substance, a map of its atomic structure must be obtained. This map can only be drawn by using X-ray crystallography.
Few scientists have been more successful at this than British chemist Dorothy Hodgkin (1910-). During World War II (1939-1945), Hodgkin and her colleagues determined the structure of penicillin. The synthesis of this drug was necessary for mass wartime production. Since then Hodgkin's team has worked on the mapping of vitamin B12, the vitamin prescribed to prevent pernicious anemia (a chronic blood disorder characterized by weakness and pallor). The team also worked on mapping insulin. Insulin is used in the treatment of diabetes (another blood disorder).
Other researchers have used X-ray technologies to record the structures of proteins, hemoglobin, and the double-helix of DNA structure (deoxyribonucleic acid).
Creating a New Science
The development of X-ray crystallography also created the science of mineralogy. Once the inner structures of many minerals were determined, mineralogists were able to define the major mineral groups. The understanding that stems from crystallography has also allowed scientists to construct the man-made minerals used in industry.