[phenixbb] Bias in Rfree

["Weiergräber, Oliver H."]

Hello,

while refining a structure with NCS, I was re-considering this paper from Michael Chapman's group:

Fabiola F, Korostelev A, Chapman MS. Bias in cross-validated free R factors:
mitigation of the effects of non-crystallographic symmetry. Acta Crystallogr D
Biol Crystallogr. 2006 Mar;62(Pt 3):227-38.

In essence, they suggest to exclude from the working set reflections that are
(1) related to a test reflection by NCS
(2) adjacent to a test reflection and its NCS mates in reciprocal space

They have implemented this strategy in a CNS module (R-free2005), but the software is no longer actively supported.
Does anybody know if something similar has ever been implemented in other software packages such as phenix?
Or am I missing any significant downsides of the approach - apart from a reduction of the working set?

Best regards,
Oliver



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  PD Dr. Oliver H. Weiergräber
  Institute of Complex Systems
  ICS-6: Structural Biochemistry
  Tel.: +49 2461 61-2028
  Fax: +49 2461 61-9540
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