Paul,
Does your lower resolution structure have the same unit cell as the
model used for MR? If your two crystals are the same except for the
presence of the ligand, then you need to make sure to keep the same
Rfree set for both. Otherwise, some reflections that were previous in
the Rwork set will now be in the Rfree set, but they are not really
free because the model was previously refined using these reflections.
Greg
On May 30, 2010, at 8:15 AM, Paul Lindblom wrote:
Hi everybody,
once more I need your help. I solved the structure of an enzyme at
resolution of 1.9 A. Now I was trying to get a complex and soaked
some ligand to my crystals. I could solve the structure (and see
poor density for my ligand or something else) at 3.0 A by molecular
replacement using my 1.9A structure as a starting model. But the
problem is now, that I got an R-work of 16.34 and an r-free of
20.23 for the new 3.0 A structure - without adding any waters or
solvent/ligand molecules. The r-factors are even better than the
ones I got for the 1.9A structure. So I think something is wrong
with the whole thing. I observed twinning for both data and used
the twin refinement option in refmac, but the results stay more or
less the same.
Any suggestions what to do? Thanks a lot,
Paul
--
Department of Biophysics
Johns Hopkins University
302 Jenkins Hall
3400 N. Charles St.
Baltimore, MD 21218
Phone: (410) 516-7850 (office)
Phone: (410) 516-3476 (lab)
Fax: (410) 516-4118
gdbow...@jhu.edu
