Victor 'P 21 2 21' *is* the conventional indexing if a <= b <= c, i.e. it's the setting agreed for deposition of crystal structures by the IUCr and the US National Institute of Standards & Technology (NIST) since 1983: it just doesn't seem to have been agreed by a dwindling number of individual program authors. AFAIK Arp/Warp is the only significant program relevant to PX which doesn't recognise the complete set of conventional settings (as defined in $CLIBD/syminfo.lib and symop.lib). In this case, the transformed setting 'P 21 21 2' (corresponding to the unconventional cell a <= c <= b) is called the 'standard' setting and is the reference symbol used for example as the title of the relevant page in ITC vol A, since for convenience the alternate settings 'P 2 21 21', 'P 21 2 21' and 'P 21 21 2' are all shown on the same page.
> seems to be a 'non-standard' setting. Refmac also has > problems with this > spacegroup, reindexing to P21 21 2 fixed the problem for me. > > Clemens I've not had any trouble with this spacegroup when using a recent version of Refmac/CCP4: are you by any chance using an old version (either of Refmac or CCP4)? If not could you post the relevant error message so the problem can be identified & fixed, as it certainly ought to work. Re-indexing is usually not a viable option for us as it causes a lot of pain with our automated processing: if re-indexing really becomes unavoidable then it means we have to delete all the processed data for that crystal and other datasets of the same crystal form, then start all over again from data processing (i.e. from the MOSFLM/D*trek step), so that all datasets & co-ordinates associated with a project in the database are indexed the same way. Having datasets around with different indexings (particularly as happened once if 2 of the cell lengths are very similar) is a recipe for chaos! Anyone trying to automate structure solution would likely run into the same problem, unless of course they anticipated this eventuality in the database design. So yes, making all software accept the internationally recognised conventions could save us a lot of work! -- Ian > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Victor Lamzin > Sent: 10 June 2008 16:45 > To: PhilEvans > Cc: [email protected] > Subject: Re: [ccp4bb] Arp/warp space group P 21 2 21 > > Dear Phil, > > One reason has been simplicity - many ARP/wARP modules operate with > space group number only. For space group 18 this would mean P21212. > Using space group name might be less robust - I remember some > compatibility problems when CCP4 introduced spaces into space group > names, this broke some of the parsers, including > simple-minded ones from > ARP/wARP. > > If there is, however, a strong wish for ARP/wARP to support > 'unconventionally' indexed space groups - then we will > certainly try to > introduce it. > > With best regards, > Victor > > > > PhilEvans wrote: > > Is there a reason why Arp/warp doesn't like space group P 21 2 21? > > > > Phil > > > > > > Disclaimer This communication is confidential and may contain privileged information intended solely for the named addressee(s). It may not be used or disclosed except for the purpose for which it has been sent. If you are not the intended recipient you must not review, use, disclose, copy, distribute or take any action in reliance upon it. If you have received this communication in error, please notify Astex Therapeutics Ltd by emailing [EMAIL PROTECTED] and destroy all copies of the message and any attached documents. Astex Therapeutics Ltd monitors, controls and protects all its messaging traffic in compliance with its corporate email policy. The Company accepts no liability or responsibility for any onward transmission or use of emails and attachments having left the Astex Therapeutics domain. Unless expressly stated, opinions in this message are those of the individual sender and not of Astex Therapeutics Ltd. The recipient should check this email and any attachments for the presence of computer viruses. Astex Therapeutics Ltd accepts no liability for damage caused by any virus transmitted by this email. E-mail is susceptible to data corruption, interception, unauthorized amendment, and tampering, Astex Therapeutics Ltd only send and receive e-mails on the basis that the Company is not liable for any such alteration or any consequences thereof. Astex Therapeutics Ltd., Registered in England at 436 Cambridge Science Park, Cambridge CB4 0QA under number 3751674
