Case Study 3: Protein Structure Determination

Structural biology is now central to very wide ranging investigations of gene function and drug discovery. X-ray crystallography (XRX) is the main tool for determining protein structure. But XRX has some specific limitations: it relies on the electron density deduced from diffraction patterns taken from crystals to identify the presence of metal ions, but cannot in general unambiguously assign the atomic number of the metal or evaluate the stoichiometric ratio of the number of ions present per protein molecule.