Dear Anita,
I happen to have a very similar problem today.
Does XDS use the desired setting if you provide it with the correct cell and
space group during the IDXREF step? You can otherwise re-index in CORRECT.
To comment on Phil:
I fed the mtz-file from pointless into ctruncate (or maybe it was scala) which
left the space group string (P2 21 21) but turned the space group number 18 into
3018 - this does screw up autosharp and maybe also other programs which use the
space group number/ symbol and not the symmetry operators.
Tim
On Thu, Mar 31, 2011 at 04:28:18PM +0200, Anita Lewit-Bentley wrote:
> Dear all,
>
> I would like to share my experiencde with a rather unexpected
> problem of indexing conventions. Perhaps I can save people some
> time....
>
> I have a crystal in the more unusual P21212 space-group (No 18). Its
> unit cell lengths are b>a>c (please note). I systematically use XDS
> for data integration, since so far it was able to handle even the
> most horrible-looking spots.
>
> Now XDS indexed my data in space-group 18, but with the axes order
> a<b<c! It had, in fact, "invented" a space-group P22121, which does
> not exist. I did not realise this until I had spent a couple of
> weeks with beautiful peaks in rotation functions, but hopeless
> results in translation functions. It wasn't until I looked more
> closely into the definition of the screw axes that I realised the
> problem.
>
> POINTLESS does not allow a reindexing of reflexions within the same
> space-group, but fortunately REINDEX did the trick at the level of
> intensities, because I like to use SCALA for careful scaling of my
> data.
>
> So, basically, beyond just warning people who might encounter
> similar problems, I was wo,dering if XDS could perhaps reindex
> reflexions according to Int. Table conventions once the screw axes
> of a crystal system have been identified?
>
> With best wishes,
>
> Anita
>
>
> Anita Lewit-Bentley
> Unité d'Immunologie Structurale
> CNRS URA 2185
> Département de Biologie Structurale & Chimie
> Institut Pasteur
> 25 rue du Dr. Roux
> 75724 Paris cedex 15
> FRANCE
>
> Tel: 33- (0)1 45 68 88 95
> FAX: 33-(0)1 40 61 30 74
> email: [log in to unmask]
>
--
--
Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen
phone: +49 (0)551 39 22149
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