Protein crystallography is an important tool to determine the three dimensional structure of a target protein at atomic resolution. A well-defined protein structure allows some insight into shape as well as physical properties of a protein in general and its active site in particular.

Target proteins must be obtained in "large" amounts (some milligrams) and very high purity in order to initiate successfully crystallization trials applying multiple conditions. Suitable crystals are absolutely crucial and must be identified and tested for diffraction of X-rays. Eventually a set of X-ray diffraction patterns of a crystal must be measured.

Applying powerful computers and multiple programs allows to determine the three dimensional coordinates of proteins and small molecules interacting with it from measured diffraction data. 

After obtaining structural information protein small molecule interactions can be studied and iteratively optimized to find a highly specific tight-binding molecule that can be used as a drug.