Have you used pointless to examine possible spacegroups? It is possible
to get one lattice point out and get a very high rsym
pointless will check these possibilities for you
The cell could be this:
C m m m 39.6 149.9 18.2 89.9 90.0 90.0 0.10 [-k,-k-2l,h]
You need to go back to the processing step I think..
Eleanor
Poul Nissen wrote:
You mention that your Rsym is 0.6 - this seems outrageously high (except if the
0.6 is just for your outer resolution bin). If 0.6 is indeed the overall Rsym
you have a basic problem of unit cell and space group assignment to reconsider.
Check if your processing accounts for all spots and check the input beam
position - if its wrong you may have mis-indexed by one (e.g. on l,
corresponding to the longest axis of your unit cell - c)
Later on: if you have any sulphurs in the structure you might consider
sulphur-SAD to complement your MR. Let the MR find your S positions and go from
there.
Poul
On 12/07/2010, at 05.00, 孙庆祥 wrote:
Dear ccp4 experts,
I'm a beginner and have a problem with the following structure solution. I need
great help from you experts. Thanks in advance!
The dataset is 1.6A resolution and the spots looks ok, except some smear in the
higher resolution. Space group is P1(could be P2 or P21). Completness is above
95% and mosaicity is less than 1. Rsym is 0.6.
Cell parameters are: a=18.2320 b= 39.6330 c=77.5260 alpha=104.8230 beta=90.0780 gamma=90.0400
The model is about 60 amino acids snake venom protein with 60% identity.
However, no solution with an initiall R less than 0.7 was obtained by Molrep,
Phaser, or Phenix .
Using a molrep search result (R=0.75, mtz in P1, 2 moelcules in AU), with
Refmac5 twin refinement, we could refine the structure to 40% Rfree and
38%Rwork. The density looks good (can see hole in rings structures) for all
residues and no continous unexplained density is observed. However, the R and
Rfree does not go down no matter what we try...
We tested the twinning by CNS or the crystal twinning server
(http://nihserver.mbi.ucla.edu/Twinning/) and found no twinning present.
I'm sure the sequence is correct.
I've tried hard on this for quite some time. Really appreciate if you could
help.
Thanks and regards,
Jeremy
