Figure 2
Difference density map results with Fourier coefficients (F1 - F2)exp(i[varphi]) based on the presence or absence of scattering contributions in the data and/or model. If neither an Fo nor an Fc contribution is present, the difference map becomes meaningless. Interpretable positive omit difference density (i.e. a difference density map calculated from the model with the ligand omitted) is therefore the primary evidence providing distinct proof for the presence of a ligand.  [article HTML]

© International Union of Crystallography 2013