Hi Dale, That is right! And that is what I concluded yesterday yet I somehow forgot all that overnight. Starting a new job and commuting 4 hours a day has taken a toll on my brain. I am an idiot. -Yarrow
I'm puzzled. Didn't you say that the translation of your ncs two-fold was not equal to half the "a" cell edge? If it is not a translation of 1/2 (in fractional coordinates) then it cannot be a crystallographic symmetry element and your space group cannot be P212121. Unless this condition is met, the similarity of your molecules is unimportant.
Dale Tronrud
On 10/17/2013 12:48 PM, Yarrow Madrona wrote:
I am doing restrained NCS refinement and would like to know how to set the target weight of the cartesian restraint in the command line? I also found a sigma value in the GUI. I read that I can decrease it in order to increase the NCS restraints. However, I have seen this under Torsional restraints. Does this also apply to cartesian restraints?
I am doing this so that I can look at the differences in position and B-factors of two molecules in the ASU that I am trying to determine are related by a perfect or imperfect 2(1) screw axis. (I posted a question about this on the CCP4 bullitan board.) If the values between molecules are exactly the same then presumably the space group is actually P212121 with 1molecule in the asu instead of P21 with two molecules. I already know that the P21 dimer superimposes almost exactly on the P212121 monomer and it's symmetry mate. I just don't know how "perfectly" they align and I am hoping this approach will tell me. I hope this makes some sense.
-Yarrow
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-- Yarrow Madrona Graduate Student Molecular Biology and Biochemistry Dept. University of California, Irvine Natural Sciences I, Rm 2403 Irvine, CA 92697