Good point. One should always check all the screw axis combos. Not fun
for P422, but Phaser makes this very easy, as it will do all the
possible screw axis combinations in one job. The correct space group and
MR solution is usually very obvious if the model is acceptable and the
MR parameters have been set reasonably. I think Open-EPMR will also
examine screw axis combinations now, but I've never used it to do this.
Cheers,
Roger Rowlett
Phil Evans wrote:
Perhaps obvious - are you sure the space group is C222 not C2221?
Phil
On 25 Jul 2008, at 14:19, Roger Rowlett wrote:
Carl Soja wrote:
Dear all
I tried to solve one structure by ccp4i molrep(resolution at 3.0 A,
space group C222, sequence ID 30%). I can get a good Rfactor 0.528
at first translation function. However, the second translation
function Rfac is 0.526, the third is 0.525, the fourth is 0.525.
All of the translation function Rfacs are too closed. I changed
the model and minimum resolution for search, the Rfactor closed no
any improved. My structure estmates four molecules in the
aymmetric unit. This is my first time found the closed Rfac by
molrep. From the low translation function Rfac, it seems that it
is correct solution. I checked the solution and found some clashes
in the structure.I am not sure why the Rfactor too closed in next
the molecule search? I know this is unusual solution by molrep.
Does it mean the diffraction data has problem?
Any suggestions are welcome.Thank you in advance!
Carl soja
To be honest, I would try both Phaser and EPMR (now Open-EPMR) first
to do MR. Both especially excel at finding good MR solutions for
multimers, and are very fast as well. These programs can find
solutions that are very difficult to find using other rotation-
translation programs, including MOLREP. In my experience (using
Phaser and EPMR) reasonable MR solutions almost always have an R-
factor under 50%.
Cheers,
--
------------------------------------------------------------------------
Roger S. Rowlett
Professor
Colgate University Presidential Scholar
Department of Chemistry
Colgate University
13 Oak Drive
Hamilton, NY 13346
tel: (315)-228-7245
ofc: (315)-228-7395
fax: (315)-228-7935
email: [EMAIL PROTECTED]
