A crystallographer is a scientist who determines the arrangement of atoms within crystalline solids to understand their fundamental properties and behaviors. This work exists at the intersection of several scientific fields, including chemistry, physics, biology, and materials science. The information they uncover is used by other scientists to support new discoveries and technological development.
The Science of Crystallography
Crystallography is the science that examines the structure of crystals. A crystal is a solid material whose atoms are arranged in a highly ordered, repeating pattern, which distinguishes these materials from amorphous solids where atoms are arranged randomly. This internal regularity is what defines a crystal. The predictable arrangement allows scientists to determine its structure down to the atomic level.
The primary method used to study these structures is X-ray diffraction. When a beam of X-rays is directed at a crystal, the ordered atoms cause the beam to scatter in a specific and predictable pattern. This occurs because the wavelength of the X-rays is similar to the distance between atoms in the crystal. The resulting diffraction pattern acts like a unique fingerprint for that crystal, containing detailed information about the position of every atom. Much like sunlight passing through a fine lace curtain reveals the pattern of the weave, the diffraction pattern reveals the crystal’s internal architecture.
The Crystallographer’s Toolkit
The process of determining a crystal structure begins with what is often the most difficult step: obtaining a suitable crystal. A researcher must grow or isolate a single, pure crystal that is large enough and structurally perfect, larger than 0.1 mm in all dimensions. This step can be a significant bottleneck in the research process, sometimes taking months or years of trial and error to produce a sample of sufficient quality for analysis.
Once a suitable crystal is obtained, it is mounted on a specialized instrument called a diffractometer. Inside this device, the crystal is exposed to a focused beam of X-rays and slowly rotated, allowing the beam to strike it from many different angles. As the X-rays pass through the crystal, they are diffracted by the atomic planes, and the resulting patterns are recorded by a sensitive detector. For particularly small crystals or complex structures, researchers often use synchrotrons, which produce X-ray beams millions of times more powerful than those from laboratory sources.
The final step involves computational analysis. The raw diffraction data, consisting of thousands of recorded reflections at various intensities, is fed into computer programs. Using mathematical algorithms, the software translates the diffraction pattern into a three-dimensional electron density map of the crystal. The crystallographer then interprets this map to build an atomic model, pinpointing the precise location of each atom and the chemical bonds connecting them.
Impact on Modern Science and Medicine
The insights from crystallography have contributed to many scientific advancements. One of the most well-known achievements was the determination of the double helix structure of DNA. The work of crystallographer Rosalind Franklin, whose X-ray diffraction image “Photo 51” provided a clear picture of the helical shape, was a key piece of evidence in this discovery. This structural knowledge advanced the field of genetics and our understanding of life.
Another example is the work of Dorothy Hodgkin, who was awarded the Nobel Prize in Chemistry in 1964 for determining the structures of biological molecules. She mapped the atomic arrangements of penicillin, which helped scientists understand how it fights bacteria. Later, she determined the complex structure of insulin, which has impacted the treatment of diabetes. These discoveries demonstrated the ability of crystallography to map large and complex biomolecules.
This legacy continues in modern medicine, particularly in structure-based drug design. By determining the precise 3D shape of proteins or viruses, scientists can design drugs that fit into them like a key into a lock. This approach has helped in developing treatments for diseases like HIV, where drugs were designed to block a specific viral protein whose structure was solved using crystallography. Understanding the shape of proteins involved in cancer allows for creating targeted therapies that are more effective with fewer side effects. The field is also applied in materials science to develop new materials, from stronger alloys to more efficient semiconductors.
Becoming a Crystallographer
The path to becoming a crystallographer begins with an undergraduate degree in a science such as chemistry, physics, biochemistry, or materials science. Following this, aspiring crystallographers pursue graduate studies, earning a Master’s degree or a Ph.D. that provides specialized training in the theories and techniques of crystallography.
Success in this field requires several skills. Patience and meticulous attention to detail are needed, as the process of growing crystals and collecting data can be slow and requires precision. Problem-solving abilities are also necessary to overcome experimental challenges and interpret complex data sets. Proficiency in mathematics and computer modeling is needed to understand the theoretical basis of diffraction and use the software that translates raw data into 3D structures.
Crystallographers find employment across several sectors of the scientific community. Many work in academia, conducting research and teaching at universities. The pharmaceutical and biotechnology industries are major employers, where crystallographers contribute to drug discovery and development programs. Government research laboratories and materials science companies also rely on their expertise.