Whose idea was it to pass X-rays through a salt crystal and see what happened? In 1912, Max von Laue and his colleagues at Munich University did just that. The effect was astonishing. An image, projected onto X-ray film, contained several dark spots (Figure 1a). This pattern could be deciphered to reveal the shape of the molecule (in this case copper sulfate, see Figure 1b and background image) inside the crystal. Thus, the technique of X-ray crystallography was born. It did not take long for scientists to realise the power of this method, and throughout the twentieth century it became possible to visualise the shapes and structures of many different types of molecules using X-ray crystallography.
Being able to ‘see’ a molecule helps us to understand how it works. In 1953 James Watson, Francis Crick and colleagues interpreted by eye the unusual X-ray diffraction pattern (Figure 2a) produced by fibres of DNA (deoxyribonucleic acid). They built a three-dimensional model showing that DNA formed a double helix, with two spiral sugar-phosphate backbones supporting a ladder of nucleotide base pairs.
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