Any twinning is due to overlapping diffraction patterns from two or more different crystal fragments. This means that the "intensity" measured is in fact the sum of two or more different I(hkl) s eg in your case* I(hkl) obs* actually equals *I(h k l ) + sc (I -h -k l)* . The diffraction can look perfect for either meridral twins or non-merihedral twins if the crystal axes are exactly related. (There is a clear explanation in the $CCP4 documentation - *Twinning (CCP4: General)**NAME**twinning - dealing with data from twinned crystals* *etc etc *
Split spots usually occur from crystal defects. The integration programs try to screen out the smeary parts of the mage and can lead to lost information.. Cheers - ask again if this isnt clear Eleanor On Fri, 12 Mar 2021 at 10:44, Flavio Di Pisa <dipi...@gmail.com> wrote: > Hi Marina, > this paper might help you for you thesis > > Effects of merohedric twinning on the diffraction pattern, Acta Cryst. > (2014). A70, 106–125 (in attachment) > > Cheers, > Flavio > > Il giorno ven 12 mar 2021 alle ore 11:30 Marina Gárdonyi < > marina....@pharmazie.uni-marburg.de> ha scritto: > >> >> Hello everyone, >> >> I am a PhD student at the Philipps-University in Marburg and I am >> currently writing my thesis. >> >> I have problems to understand whether in my case twinning can be seen >> in the diffraction pattern or not. >> >> I know that it depends on the type of twinning wheter you can see it >> in the diffraction pattern. The crystal had a resolution of 2.2 A. >> During processing it seemed to have the space group P622, but in the >> end it was P3(2)21. With phenix Xtriage I found out, that the data set >> was twinned. The twin law was -h,-k,l. So it should be merohedral >> twinning. >> I read in a paper, that in case of merohedral twinning you cannot see >> it in the diffraction pattern. But in my case that seemed not to be >> the case because of splitted reflections. Or am I wrong??? >> >> I would be very happy to hear your opinion on that. Thanks in advance! >> >> Best regards, >> Marina >> >> -- >> Marina Gárdonyi >> >> PhD Student, Research Group Professor Dr. Klebe >> >> Department of Pharmaceutical Chemistry >> >> Philipps-University Marburg >> >> Marbacher Weg 6, 35032 Marburg, Germany >> >> Phone: +49 6421 28 21392 >> >> E-Mail: marina....@pharmazie.uni-marburg.de >> >> http://www.agklebe.de/ >> >> ######################################################################## >> >> 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 > ######################################################################## 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/
