I am sure you have checked this but A) is there non cryst translation? If so this can make space group selection tricky . Could it be P3 21 or P31 21 or ... B ) the twin indicators at data processing are pretty reliable and if that suggests no twinning it probably isn’t there... you could process bits separately to see if bens idea is likely.
C) I see data sets where long runs if vatches are totally wrong - Rmerge >1 etc - no idea why but you need to cut them out of the data processing All very puzzling! Eleanor On Thu, 31 Mar 2022 at 05:46, Ben Bax <ben.d.v....@gmail.com> wrote: > The twin fraction can vary during data collection - if the beam is smaller > than the crystal > For example you could have crystals which are like two very short ends of > pencils - with flat ends together (in your case these might pencils could > be in P3) > In some orientations you could have the beam going through only one pencil > (not twinned) and some orientations going through both pencils ( 50:50 > twin). > This is not yet properly handled in the data processing. > > > > On 29 Mar 2022, at 09:39, Nicholas Keep <n.k...@bbk.ac.uk> wrote: > > Just double checking that Refmac automatically handles twinning without > the need for a keyword or a box click in i2. I have a crystal in P32 21 > that gives poor Rfactors and maps (Rfree mid 40s) from what should be an > excellent model. I have reprocessed in P32, P1 and C2 but all give similar > results so it appears not to be hidden twinning. There is no need to click > a box or enter a keyword for this to be a check for twinning ? > > There is severe anisotropy and a few other problems flagged up in iSPYB so > there may be more complex problems than twinning with these crystals > > Best wishes > > Nick > > -- > Prof Nicholas H. Keep > Emeritus Professor of Biomolecular Science > Crystallography, Institute for Structural and Molecular Biology, > Department of Biological Sciences > Birkbeck, University of London, > Malet Street, > Bloomsbury > LONDON > WC1E 7HX > > Dept email n.k...@bbk.ac.uk > Telephone 020-3926-3475 (Will contact me at home if working as well as my > office) > > ######################################################################## > > 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/ > > ######################################################################## > > 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/ > ######################################################################## 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/
