Dear CCP4BBers and PhenixBBers (cross posting here, since we all read both anyhow)
to the experts out there here's my question:
We have a P21 dataset with 2 molecules in the asu and a refined twin fraction of 38% according to phenix.refine using a twin law operator.
My gut feeling tells me that I can't use NCS unless I detwin the data, is that a correct assumption ?
How does phenix.refine [PDB] [mtz] twin_law="h,-k,-l" main_ncs=true would deal with this problem ?
Same question goes to Garib, it's very convenient to just specify twin in your Refmac script without further values and magic happens but what if I add NCS restrains, will Refmac treat them correctly according to the twin operator ?
Twins are confusing in real life and even more in crystals I think.
And no the data can not be processed in a higher space group, P222 results in Rmerges of >40% in the lowest resolution shell, the beta angle is 92.4 degrees in P21. And if processed in P1 we get 4 molecules per asu and a refined twin fraction of 50%, which in my eyes clearly indicates it's not P1 but really P21.
Hope to get some interesting feedback on this issue.
Thanks,
Jürgen