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: ale...@pasteur.fr > -- -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen phone: +49 (0)551 39 22149 GPG Key ID = A46BEE1A
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