Figure 14
Density-modification techniques. (a) Solvent flattening uses automated methods to define the protein–solvent boundary and then modify the solvent electron density to be of equal value. (b) Histogram matching redefines the values of electron-density points in a map to confer to an expected distribution of electron-density values. (c) Non-crystallographic symmetry averaging imposes identical electron-density values to points related by local symmetry, in this case a trimer of ducks that forms the asymmetric unit. The local NCS symmetry operators relating points in duck A to ducks B and C are shown. |