Evil Twin example
Data that exhibit twinning represent a relatively common challenge for structure phasing and refinement in X-ray crystallography. This dataset exhibits hemihedral twinning with a twin fraction near 50% and will demonstrate the steps that must be taken to successfully refine the structure.
Merged reflection files are available for data generated by James Holton using his MLFSOM program, which relied on the deposited structure factors to calculate spot intensities in simulated diffraction images that were then processed using his Elves data processing program. Three merged reflection files are available representing three different twin fractions, which demonstrate nicely the increasing difficulty associated with increasing twin fraction. See James' notes here.
Useful Information
Data kindly provided by: James Holton
Sample: I1 domain from the human giant muscle protein titin
PDB Code: 1G1C
Merged reflection files:
20% twin fraction
40% twin fraction
50% twin fraction (truly an evil twin)
Phased/refined Structures and Instructions
| CNS | PHENIX | Refmac | BUSTER | SHELX | |
|---|---|---|---|---|---|
| PDB Files | TBA | TBA | TBA | TBA | Bundled files |
| Log File | TBA | TBA | TBA | TBA | Bundled files |
| Author Instructions | Axel Brünger | Pavel Afonine | Garib Murshudov | Gerard Bricogne | George Sheldrick |
| SFCheck Output | For CNS file | For PHENIX file | For Refmac file | For BUSTER file | For SHELX file |
