Problems of Pseudo Symmetry
Direct-method Treatment of Phase Ambiguities due to Pseudo symmetry
Background
Pseudo symmetry is due to part of the structure
having a higher symmetry
than that of the whole structure. Phase ambiguities often occur in solving
this kind of structures. Direct methods have been introduced to deal
with this problem.
There are two kinds of pseudo
symmetry, i.e. enantiomorphous and translational pseudo symmetries. Direct-method treatment of
the former led further to breaking phase
ambiguities in protein crystallography , while that of
the latter led further to ab initio
determination of incommensurate modulated and composite structures.