Hi Charlie, With xia2 you can try to reprocess and force the spacegroup to be P222 and the cell dimensions to be the larger option with the following options:
-spacegroup P212121 -cell 80,80,120,90,90,90 This can also be done with other processing pipelines. I've seen similar cases before and you may find that the P222 cell was found but then discarded during the automatic processing as F222 fit just a little bit better. If collecting data at Diamond, it is worth uploading the expected spacegroup / cell dimensions and then the pipelines will try to process the data in the given cell as well as 'ab initio'. Hope this helps, Andy ________________________________ From: CCP4 bulletin board <[email protected]> on behalf of Nichols, Charlie <[email protected]> Sent: 08 July 2024 12:07 To: [email protected] <[email protected]> Subject: [ccp4bb] Lattice expansion External Sender: Use caution. Hi, I am trying to recapitulate a published crystallisation system. The published crystal form is P212121 approx cell dimensions 80, 80, 120 // 90, 90, 90 with one trimer in the ASU We did not get any crystals in the published conditions but have found a new condition giving data to a much higher resolution than the published one but there is a problem… New crystal form is F222 with approx cell dimensions 40, 40, 120 // 90, 90, 90 – this cell is too small to fit one monomer let alone one trimer. The prep is remarkably clean and there is a high volume of crystals in the drop so unlikely to be a contaminant. I have tried molrep with individual domains in case there has been degradation during crystallisation but this does not look at all promising. I am wondering, given the almost exact halving of the a/b cell dimensions and almost exact equivalence of the c cell dimension, whether this is a particularly egregious form of twinning where the twin is three 2-fold screw axes to cause an apparent reduction in the unit cell. Is there a way to expand the data from the current 40, 40, 120 // 90, 90, 90 unit cell to the larger ‘super-cell’ 80, 80, 120 // 90, 90, 90 with four copies of the data to then attempt either molep or just twin refinement with the original published model? Any comments / help appreciated – NB: I can’t share the actual data or even the target as they are confidential client data… Thanks, take care, Charlie Nichols ________________________________ To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 The Francis Crick Institute Limited is a registered charity in England and Wales no. 1140062 and a company registered in England and Wales no. 06885462, with its registered office at 1 Midland Road London NW1 1AT ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
