X-ray crystallography of proteins

X-ray Diffraction of Proteins
Kate Thomas, School of Optometry and Vision Science
X-ray diffraction has been used as a vital method for studying the structure of proteins
for many decades. Currently over 49000 crystal structures of proteins, nucleic acids
and other biological molecules have been determined using X-ray diffraction,
demonstrating the significant value of this method [1].
X-ray diffraction is conducted at either synchrotron radiation sources or using
laboratory based systems; in both cases similar principles are involved. Crystals
within the protein structure diffract X-ray beams and produces a characteristic twodimensional pattern of reflections. The position and intensity of each reflection can
be calculated in a straight forward manner, but the phases of the waves which form
each reflection must also be determined in order to produce an electron density map.
Combinations of experimental and computational methods are typically used to solve
the phase problem. The electron density map can be used to build an atomic model,
which is then refined against the X-ray diffraction data.
This presentation will provide an insight into X-ray diffraction as a technique and
explore the benefits when determining protein structure.
[1] http://www.rcsb.org/pdb/statistics/holdings.do