You don't mention your space group, it could be one with two distinct
"settings." I.e. that a reindexing would be necessary to switch from one
set of data to the other. If you scale the two datasets together, is the
Rmerge reasonable, or is it over 30%?
-
=======================================================================
You can't possibly be a scientist if you mind people
thinking that you're a fool. - Wonko the Sane
=======================================================================
David J. Schuller
modern man in a post-modern world
MacCHESS, Cornell University
[log in to unmask]
On Sun, 2009-08-09 at 10:39 -0400, kumar wrote:
> Dear CCP4ers,
> I refined a 3.4 A SAD data in refmac ( using the 'SAD data directly' option
> ) and reached a plateau with an Rfree of 36%. Then I tried to extend phases
> with the 2.95 A dataset which has no anomalous data (I maintain the same
> Rfree flag). The maps look like a moderately good fit, but the Rfree doesn't
> go below 39%.
> With Autobuild in phenix, map looks good and Rfree went down to 36% but
> doesn't change further. Deletion of a 10 residue loop for which no density
> is visible increases Rfree.
> Model bias is still persistent as sidechains deleted earlier don't come
> back. Finally, even with the good density-model fit, there are huge areas of
> negative difference density and few areas of positive density.
> I also tried a round of simulated annealing in CNS, but it didn't change the
> Rfree. Playing with the weights hasn't made much difference either. TLS
> refinement also doesn't make any difference. Any ideas how to go about?
> Thank you.
> Kumar
