A full-symmetry translation function based on electron density

A method for positioning an oriented fragment within the unit cell is presented. It is based on a correlation between a model and observed data which is performed in Fourier rather than Patterson space. Symmetry-related molecules are located in the electron density map calculated in space group P1, with the phases derived from a model that is correctly oriented but arbitrarily positioned in the unit cell. It is shown that considering all symmetry elements simultaneously substantially increases the sensitivity of the method and makes it less susceptible to the errors in the model. The procedure also automatically incorporates a penalty for the overlap of symmetry-related molecules, and the stringency of this requirement is easily modified. The method has been tested on two different proteins and the results compare favorably with other translation functions.