A phased translation function

A phased translation function, which takes advantage of prior phase information to determine the position of an oriented molecular replacement model, is examined. The function is the coefficient of correlation between the electron density computed with the prior phases and the electron density of the translated model, evaluated in reciprocal space as a Fourier transform. The correlation coefficient used in this work is closely related to an overlap function devised by Colman, Fehlhammer & Bartels [in Crystallographic Computing Techniques (1976), edited by F. R. Ahmed, K. Huml & B. Sedlacek, pp. 248-258. Copenhagen: Munksgaard]. Tests with two protein structures, one of which was solved with the help of the phased translation function, show that little phase information is required to resolve the translation problem, and that the function is relatively insensitive to misorientation of the model.