RECIPROCAL-SPACE MOLECULAR-REPLACEMENT AVERAGING

The molecular-replacement equations, in which electron-density averagi ng and skew averaging have been unified, were used in reciprocal space to refine and extend the resolution of phased reflections. A procedur e has been developed for the treatment of molecular envelopes of gener al shape. The equations were successfully applied to the reflection da ta of bacteriophage phi X174 (60-fold redundancy). Truncation of the G diffraction function beyond the first few nodes did not have a signif icant effect on the quality of the molecular-replacement equations. Re ciprocal-space molecular-replacement averaging should prove to be a us eful alternative to real-space averaging. Strategies are discussed tha t are possible only in reciprocal space.