[phenixbb] refinement with twinning

alexander.singer at utoronto.ca alexander.singer at utoronto.ca
Wed Feb 16 11:52:43 PST 2011

Hi -- I have a twinned data set -- approximate twinning fraction of  
0.4.  I decided to try to try twinned refinement using phenix.refine  
in what would seem to be the appropriate manner -- from the "All  
Parameters" menu, I select twinning, hit "Run Xtriage now" on my mtz  
file, it gives me the input to the "Twin Law", I keep the rest of the  
values the same (gave no Anisotropy correction), hit OK, then run 3  
cycles of refinement.  The only thing is that the Rwork/Rfree values  
are really very good, almost too good to be true -- for my 1.7 A  
refinement, I have values of 12.4 and 14.8%, respectively for Rwork  
and Rfree. Is there anything that I may be doing wrong yielding R  
values which are artifically too low?

Thanks for your help


Dr. Alex Singer
C.H. Best Institute
112 College St. Room 70
University of Toronto
Toronto, Canada, M5G 1L6

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