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
> <[log in to unmask]
>> 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
>>
>> --
>>
>> ***************************************************************
>> * Clemens Vonrhein, Ph.D. vonrhein AT GlobalPhasing DOT com
>> *
>> * Global Phasing Ltd.
>> * Sheraton House, Castle Park
>> * Cambridge CB3 0AX, UK
>> *--------------------------------------------------------------
>> * BUSTER Development Group (http://www.globalphasing.com)
>> ***************************************************************
>>
>
>
>
>
--
Professor Eleanor Dodson
YSNL, Dept of Chemistry
University of York
Heslington YO10 5YW
tel: 00 44 1904 328259
Fax: 00 44 1904 328266
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