I had a similar problem to what you describe. In my case the dataset was severely anisotropic (2.6A, 3.4A, 4.6A in each axis). The R factors were stuck similar to yours but the map looked good. I was told by someone with a much better appreciation of the theory than myself that the anisotropy was causing the problem.
It would be interesting to know from an expert in anisotropy e.g. the creators of UCLA anisotropy server or Startaniso whether anisotropy can cause this problem and whether there is any way around it. Cheers, Paul Paul Steven Miller (PhD) Postdoctoral Researcher University of Oxford Wellcome Trust Centre for Human Genetics Division of Structural Biology Roosevelt Drive Oxford OX3 7BN ---- Original message ---- >Date: Fri, 13 Oct 2017 10:30:22 +0200 >From: CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> (on behalf of Gianluca Cioci ><gianluca.ci...@gmail.com>) >Subject: [ccp4bb] High R/Rfree after MR >To: CCP4BB@JISCMAIL.AC.UK > > Dear All, > I am trying to refine a structure at 3.3A. Model has > 60% identity to the target. Maps look OK (for 3.3A) > and rebuilding in Coot is relatively > straightforward. However, after some rebuilding > cycles the R factors are stuck at 0.37/0.39 > (REFMAC). > XTRIAGE tells me that everything is normal (no twin, > 98% completeness, R=3.5% in the low resolution bin), > perhaps some anisotropy is present. > I have already refined 2 homologous structures at > resolutions going from 3.2 to 3.8 and there were no > problems (final R ~ 0.21/0.24). > Any advice ? > Thanks, > GIA
