This chapter discusses the concept of density modification, where a priori information about the structure of the macromolecule being studied is used to improve phase estimates. These concepts of density modification for the improvement of phases from crystallography have been implemented in many different programs in the past. Some of the popular density modification programs implementing the real space restraints are SOLOMON (Abrahams, 1997), DM (Cowtan, 1999), and RESOLVE (Terwilliger, 2003).
Keywords: X-ray diffraction; phase measurement; electron density; density modification
Chapter. 5600 words. Illustrated.
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