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Expertise in Structural Biology

X-ray crystallography

X-ray crystallography is the most powerful approach to determine the three-dimensional architecture of biomolecules according to the Protein Data Bank (pdb). As of August 2008, the pdb holds 52400 structures of biomolecules (mainly proteins), of which roughly 85% were determined by X-ray crystallography. The first and most important step of X-ray crystallography is the crystallization of the protein of interest. Here, protein molecules form a solid lattice, in which the individual building blocks are repeated in a regular fashion in all three dimensions. As all other crystals, protein crystals scatter X-rays, which is radiation of a wavelength of roughly 1 Å (1 Å= 10-10 m). This scattering, i.e. the change of the X-ray after interacting with the protein crystals can be used to derive the atomic structure of a protein or any other biomolecule with an accuracy around 10-10m. Thus, atomic information become available which is the prerequisite to understand the function of proteins with respect to catalysis or the role of disease-related mutations. Equally important is the structural information derived from X-ray crystallography in applications of protein engineering, drug design or protein evolution. Only structural information provides us with the necessary knowledge to understand or eventually modify the function of biomolecules.

Figure Legend:
A - Crystal composed of the nucleotide binding domain of a membrane protein
B – X-ray diffraction image of the above crystal
For further information see: Zaitseva J. et al. (2004), Acta Cryst. (2004). D60, 1076-1084

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