Written by Jarrod Green
Both these machines are X-ray diffractometers. The one on the left is from the 1970s, while the one on the right is from the present day.
Image: CSIRO
If Lawrence Bragg was still alive he really could be boastful. This November marks the centenary of crystallography. It’s a powerful technique Bragg helped to develop for studying the structure of chemicals.
Born in Adelaide, Lawrence remains the youngest person ever to win a Nobel Prize, the most prestigious award in science. Lawrence was just 25 years old when he shared the 1915 Nobel Prize in Physics with his father William.
Bragg’s work is still important today because it forms the basis of X-ray crystallography, a method for determining how atoms are arranged in a crystal. This kind of structural information is important for developing new technologies such as materials and medicines.
When a beam of X-rays strikes a crystal, the atoms in the crystal cause the X-rays to bend and spread out, forming a distinctive pattern. This phenomenon is known as diffraction and occurs when electromagnetic waves, such as visible light or X-rays, encounter an obstacle or narrow opening.
The resulting diffraction pattern for each substance is unique and depends on the spacing and arrangement of atoms within the crystal. Using Bragg’s famous law, it is possible to interpret the diffraction pattern and determine how the atoms are positioned within the crystal.
Table salt and diamonds were some of the first crystals to be studied by the Braggs using X-ray crystallography. Since then, the technique has been used to study the structure of countless substances. Perhaps most famously, it was used to determine the double helix structure of DNA, the chemical instructions on which life is based.
Understanding the chemical structure of substances helps scientists understand their properties, so it can be an important step in solving difficult problems. CSIRO scientists are using X-ray crystallography to study the structure of a protein found in the brain called amyloid beta. This protein is associated with Alzheimer’s disease, which results in memory loss. Understanding the structure of amyloid beta may help find a treatment for the disease.
So Lawrence Bragg is one person who might deserve to be just a little bit immodest. The method he helped to develop one hundred years ago remains one of the most important and powerful tools for investigating chemical structure today.
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