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Dear Yuri

1) For twin refinement refmac internally changes free reflections so that twin related reflections belong to the same class (twin or working). However it would be good to generate free reflections in higher space group that would include twin and space group symmetries. 
2) You should always use original data for refinement. Never use output from refmac for next round of refinement. Output mtz file is representation of model.

regards
Garib
 
On 2 Oct 2011, at 03:27, Yuri wrote:

Dear all,
I have some questions about the correct protocol for refinement of twinned data (0.46)

1- How do I ensure that my Rfree set is generated properly?

2-I noticed that if I enable intensity based twin refinement, refmac estimates the correct twin fraction
law -h,-k,h+l. But for subsequent refinement rounds should I keep using the raw intensity mtz file or
the newly generated mtz with PHIC and FOM information?

Thank you
--
Yuri Pompeu

Garib N Murshudov 
Structural Studies Division
MRC Laboratory of Molecular Biology
Hills Road 
Cambridge 
CB2 0QH UK
Email: garib@mrc-lmb.cam.ac.uk 
Web http://www.mrc-lmb.cam.ac.uk