A Subgroup Algorithm to Identify Cross-Rotation Peaks Consistent with Non-Crystallographic Symmetry
Ryan H. Lilien, Chris Bailey-Kellogg, Amy C. Anderson, and Bruce R. Donald
Acta Crystallographica D, 2004; 60: 1057-67.


Refined ChDHFR-TS dimers have a non-crystallographic 51 axis (O’Neil et al. 2003).  By analyzing the cross-rotation peak list, CRANS was able to identify the five correct dimer orientations. 
(Left) A portion of the unit cell containing the 51 screw axis of ChDHFR-TS. The dimerization axis of Dimer 3 is coincident with a crystallographic 2-fold. Dimers x and x' are related by a crystallographic 2-fold. The crystallographic a and c unit cell edges are shown for reference. (Right) Top-down view showing the 5-fold symmetry.

O’Neil, R., Lilien, R., Donald, B., Stroud, R. and Anderson, A.: 2003, Phylogenetic classification of protozoa based on the structure of the linker domain in the bifunctional enzyme, dihydrofolate reductase-thymidylate synthase, J. Biol. Chem. 278, 52980–52987.