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How did you create to this model? Was the gap between R and Rfree this
high from the very beginning? If not, try to find out where the gap became
so high.

- - did you introduce too many water molecules? You can overfit your data
  this way by pretending noise were waters
- - do you have to tighten the weights of stereochemical restraints? If you
  use refmac5, try setting it to 'AUTO' or something below 0.1. A good
  indicator off the weight being too high is the list of rmsd's at the end
  out the refmac5 logfile.

Look at your difference map (fofc) at +/- 3 sigma, not 2 sigma. You want
that map to show as little density as possible (either 3 or 2 sigma, but 3
is more realistic, I dare say).

Tim

- --
Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen

GPG Key ID = A46BEE1A


On Wed, 5 Jul 2006, [gb2312] Li Sheng wrote:

> ***  For details on how to be removed from this list visit the  ***
> ***          CCP4 home page http://www.ccp4.ac.uk         ***
>
>
> Hi, dear all,
>
> Please do me a favour. I ever collected a data set of 2.7A. The space
> group is C2. The model fit the 2fofc map and the omit map very well. The
> R factor
>  is 0.26 now but R free is 0.37 and can not be minished. What kind of
> error can cause such a gap between R factor and R free?
> Thanks in advance.
>
>
> Sincerely yours,
> Li
> 2006.06.07
>
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