X-ray crystallography is a process used to determine protein structure.
The protein of interest is purified and crystallised by freezing the sample in liquid Nitrogen. X-rays are then fired at the crystal, and the scattering pattern recorded. The scattering pattern can then be used to deduce the protein structure, by using a Fourier transformation.
To form a crystal of the protein of interest, it may be necessary to mutate the protein. Some proteins loose their rigidity when they are removed from a membrane or their biological environment, so mutation can allow structures to be removed or added to improve rigidity. High purity of the sample is necessary, as well as a high concentration. This stage is generally the most difficult, due to the uncertainties the practical biochemistry involves (due to differences in biological molecules).
A synchrotron can be used to produce the X-ray beam. This is a type of particle accelerator allowing the production of a high powered X-ray beam, which gives better resolution and faster data. The higher resolution data obtained is important when studying proteins for pharmaceutical research, due to the high specificity drug molecules require.
When studying membrane proteins, detergents must be used to extract them from the bilayer. The concentration of detergent must be above the critical micellar concentration, allowing the formation of micelles. It may be necessary to use a different detergent to extract the protein from the membrane to the detergent used to stabilise the protein.
The developing technology, cryo EM, is becoming more dominant for protein structure determination, due to the improving resolution the technology provides. This allows the use of smaller and cheaper equipment to produce protein structures, while reducing the amount of complex biochemistry required.