Molecular replacement: the approach of the program REMO

A new program for molecular replacement, REMO, has been written. In the rotation step, the orientation of the model molecule is found by rotating the weighted reciprocal lattice of the protein with respect to the calculated transform of the model structure: the fitting is searched in the reciprocal space. The space group of the model structure is assumed to be the symmorphic variant of the protein space group. The algebra necessary to optimize the correlation factor between protein and model structure-factor moduli is described. The oriented model molecule is located by using the correlation function coupled with a translation function calculated by fast Fourier transforms. REMO has been successfully applied to a variety of test problems and extensively compared with other currently available molecular replacement programs.