Correlation function method in protein crystallography

A weighted correlation function as a method for computing electron‐density maps is proposed to reduce the errors of the Fourier syntheses performed on inaccurate and/or incomplete data. The formulae are revised for the difference Patterson vector search, for multiple isomorphous replacement (MIR) and single isomorphous replacement (SIR) syntheses and for the difference Fourier synthesis. The examples show that the correlation‐function approach has the potential to provide more reliable results than those obtained by conventional Fourier syntheses.