Isomorphous replacement and anomalous scattering

摘要: When two or more crystals have the same structure except for replacement addition of one a few (usually heavy) atoms, phase determination using isomorphous can be resorted to. In most practical instances, atomic form factor is real number. absorption edge an atom close to wavelength incident radiation, becomes complex and anomalous scatterer. Anomalous scattering used also determining absolute configuration. The effects are often complementary. Although they been in use from 1930s, useful applications approaches macromolecular crystallography 1950s. Robust methods developed their refinement heavy-atom positions protein derivatives calculation angles. With advent tunable synchrotron based only on become prominent. This chapter describes development area up mid-1980s. subsequent developments almost exclusively concerned with crystallography. They discussed International Tables Crystallography Volume F .