Some applications of the phased translation function in macromolecular structure determination.

Although the phased translation function was first described some time ago [Colman, Fehlhammer & Bartels (1976). In Crystallographic Computing Techniques, edited by F.R. Ahmed, K Huml & B. Sedlácek, pp. 248-258. Copenhagen: Munksgaard], it has been little used, especially in the application of molecular replacement to macromolecular structures. Nevertheless, the procedure is relatively easy to apply and deserves wider use. In this paper the versatility of the phased translation function in a number of different applications is examined and experience gained in obtaining optimal results in protein structure determination by this method is reported. Examples given show how it can be used to position an oriented fragment, to locate independent components with respect to a common crystallographic origin and to choose correctly between enantiomorphic space groups. Its performance is compared with other translation functions in common use.