Figure 9
From: Rigidity analysis of protein biological assemblies and periodic crystal structures
The asymmetric unit (a) of PDB structure 1UCS is composed of four significant rigid clusters (and many more smaller ones that are not displayed). Unlike PDB structure 2YZT (Figure 8a), none of these is substantially larger than the others. In this case, the number of significant rigid clusters in the crystal form is more than the sum of the significant rigid clusters of the asymmetric units. This indicates interactions between the units that affect the rigidity of the crystal structure.