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Dear Tobias, If you have coordinates available for the different space groups, the obvious solution is to first generate complete NCS units in the different space groups, using appropriate crystallographic symmetry and then superimpose the whole unit with something like lsqkabs. You have to watch out though, that equivalent molecules are used for the superposition. Best, Herman Von: CCP4 bulletin board [mailto:[log in to unmask]] Im Auftrag von Tobias Beck Gesendet: Freitag, 19. Juni 2015 15:07 An: [log in to unmask] Betreff: [ccp4bb] determine NCS operators from PDB coordinates Dear all, I have a PDB file that contains NCS in the asymmetric unit, probably point group D3. 1.) What program is recommended for determining the symmetry operators from PDB coordinates? I found findncs, but this uses only heavy atom coordinates (I could probably use just the sulfurs from the PDB as a work around). 2.) Then I would like to compare the PDB file to a related structure. Here I would like to align the symmetry operators determined above with symmetry elements found in a different space group, for example align the twofold axis from NCS with a twofold axis in found in a particular space group. What is a good way to go about this? I am aware that NCS is used in programs as restraints during refinement, but here I am interested in obtaining the NCS symmetry operators and aligning them to symmetry elements present in a new space group. Maybe I am overlooking an obvious solution. Any help is greatly appreciated. Thanks and best wishes, Tobias. -- ___________________________________________ Dr. Tobias Beck - independent group leader - RWTH Aachen University Institute of Inorganic Chemistry Landoltweg 1, office: 304N 52056 Aachen, Germany phone: +49-241-80-90057 fax: +49-241-80-99003 web: http://www.ac.rwth-aachen.de/extern/beck/ ___________________________________________