I think this is called "P21", with the additional annoyance that you need to pick your Rfree set in P212121 and then symmetry-expand it. Otherwise, your NCS operators will constrain your "free" reflections to have the same intensity as their "NCS mates". I'm sure you didn't make that mistake, but a lot of other people have.
I suppose you could still call this "NCS", for "nearly crystallographic symmetry". But I think the general term "pseudosymmetry" is what I would use in a paper. I have seen one case (1FYK) where the protein followed the cannonical crystallographic symmetry and the DNA was disordered along the screw of the double helix. Since O.L. was having a hard time interpreting the DNA density, he re-grew the crystals with a new oligo containing a single iodinated base to try and clear up the register, only to find that the iodine difference map lit up _every_ base in the DNA ladder, forming a beautiful double helix, with one atom! That is: all the "base pairs" in the density was actually composed of an equal portion of all the bases in the oligo. Not exactly the situation you are in, but definitely a case where one part of the ASU had different "symmetry" than another. -James Holton MAD Scientist On Mon, Oct 10, 2011 at 2:41 PM, Jon Schuermann <schue...@anl.gov> wrote: > I am sure this has happened many many times before but I cannot find a > reference. I have a protein/DNA complex structure where the protein has > P212121 symmetry, but the DNA only has P21 symmetry. I know its > pseudosymmetry caused by the NCS. Has anyone seen this with protein/DNA or > have a reference I can add to my paper? > > Thanks so much, > Jon > > -- > Jonathan P. Schuermann, Ph. D. > Beamline Scientist > NE-CAT, Building 436E > Advanced Photon Source (APS) > Argonne National Laboratory > 9700 South Cass Avenue > Argonne, IL 60439 > > email: schue...@anl.gov > Tel: (630) 252-0682 > Fax: (630) 252-0687 >
