I don't see how a self rotation function can determine SG. If you processed
data as P1 then found the SR maps showed 3 folds and 2 folds you might
suspect that POINT GROUP!!! (Remember space groups are guessed on the basis
of systematic absences - you don't really know that till you have a
structure solution)
At the integration stage it is important to choose a crystal class - e.g.
trigonal with a=b and gamma = 120 The point groups then may be P3 P312 P321
P6 P6/mmm
After integration a program like pointless checks for symmetry agreement.
eg do h k l k (-h-k),l and -h-k,h,l agree well? In that case you probably
have 3 fold symmetry.
And so on for other possible symmetry operators..
After that you can probably be confident of your point group.
But as Clemens pointed out - there are different equally possible indexing
conventions for some of these choices. You need to check pass 2 against
pass 1, etc - see pointless GUI Eleanor
On Apr 5 2012, Deepthi wrote:
Hello
I arrived at the p312 space group by running a self rotation function using
MOLREP. The maps show the space group as p312. I was scaling the data
individually for each wavelength. None of the three wavelengths are scaling
are scaling in p312 space group.
On Thu, Apr 5, 2012 at 2:17 AM, Clemens Vonrhein
<vonrh...@globalphasing.com
wrote:
Hi,
On Wed, Apr 04, 2012 at 02:07:58PM -0700, Deepthi wrote:
> Hello everyone I have a problem scaling the MAD data which was
> collected a week ago.The data was collected at 1.5A resolution using
> three wavelengths for Zn-MAD experiments. Scaling the data for MAD
> experiments, the number of
rejections
> and chi2 values were very high even after adjusting the error-scale
factor
> and error model. The space group i used was p312 which i obtained by
> running a self-rotation function in MOLREP. When i scale my data using
p312
> spacegroup the chi2 and rejections were huge. But he data was scaling
well
> in p321 spacegroup. can anyone explain whats going on?
When you say 'Scaling the data for MAD experiments': do you mean
scaling the various scans for your 3-wvl MAD data in a single scaling
job? Unless you already took care of this during data integration,
remember that your separate scans could have been indexed differently
and therefore don't match up. See eg.
http://www.ccp4.ac.uk/html/reindexing.html
for some lookup-tables in P312 and P321. You can use the CCP4 program
'reindex' on MTZ files if needed.
But I guess most modern data-processing and scaling programs will take
care of that automatically anyway?
Cheers
Clemens
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Professor Eleanor Dodson
YSNL, Dept of Chemistry
University of York
Heslington YO10 5YW
tel: 00 44 1904 328259
Fax: 00 44 1904 328266
