Macromolecular X-ray Crystallography
X-ray crystallography is an analytical method of determining the three-dimensional structure of a molecule resulting in a set of coordinates describing the location of non-hydrogen atoms in the molecule. Macromolecular X-ray crystallography focuses on very large biological molecules such as proteins, DNA and RNA. The three-dimensional structures are used to understand the relationship between the structure of a biological molecule and its function. It is also used to understand the interactions between interacting biological molecules, and between biological molecules and small molecules such as substrates, inhibitors, and pharmaceuticals. Macromolecular X-ray crystallography also is used to study the structural effects of mutations in proteins, the effect those mutations have on the structure-function relationship, protein stability, and in protein engineering.