Direct‐space methods in phase extension and phase determination. II. Developments of low‐density elimination

摘要

The low‐density elimination method for phase extension and refinement ShionoWoolfson (1992).Acta Cryst. A48, 451456 has been improved by substituting a smoother density‐modification procedure for the original sharp cut‐off function. In addition, better criteria have been found for limiting the number of refinement cycles, which gives a better final result for much less work. The effectiveness of the process has been illustrated by phase refinement for a protein with high‐resolution (1.17 Å) data containing 808 independent non‐H atoms plus 83 water molecules in the asymmetric unit; the unweighted mean‐phase error was reduced from 74 to 39.3°. Phase extension and refinement was also demonstrated for pig 2Zn insulin starting with multiple isomorphous replacement (MIR) phases at 1.9 Å and extending out to 1.5 Å. There was a significant improvement of phases and the final map had a correlation