Hi Len, Twinning does not have to be a random spatial distribution within a crystal. You can have large discrete domains that are effectively untwinned smaller crystals assembled into the larger one – we have had several cases with back-to-back growth of two crystals. In some cases, the boundaries between such macro-twin domains can have weaker crystal contacts than within each domain allowing ‘physical-detwinning’ by application of stress: https://pubmed.ncbi.nlm.nih.gov/15339801/
We have also had some success with breaking large, twinned crystals with a loop and collecting data from several individual chunks to obtain an untwinned dataset. Synchrotron beam is much smaller than in-house so in your case you were presumably lucky with the orientation / choice of centring, so you collected data mostly from one such macro-twin domain. Cheers, Charlie. From: CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> On Behalf Of Thomas, Leonard M. Sent: Monday, March 25, 2024 7:23 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] twinning or not? WARNING: This message was sent by an external party. Report suspicious messages via the “Report Phishing” button in Outlook. Hello, I have run into a very odd situation. Upon collection and data processing on a crystal on my home source all pointers seemed to show twinning. Was not surprised since previous crystals under different but related conditions have showed significant twinning though the cell dimensions were different but not the resulting apparent space group. Now the odd thing, I sent the crystal to the synchrotron figuring I might be able to get some data that might help figure out what is going on. Upon processing of the synchrotron data, SSRL 9-2, magically no twining was detected. A couple of other crystals of the same compound though not from the same exact condition showed the twinning. I processed the data using HKL, which I primarily on my home source data and XDS with similar results. In summary, the exact same crystal shows twinning on Cu home source and no twinning at all at the synchrotron. Any ideas would be welcomed. Len Leonard Thomas, Ph.D. Biomolecular Structure Core, Director Oklahoma COBRE in Structural Biology Price Family Foundation Institute of Structural Biology University of Oklahoma Department of Chemistry and Biochemistry 101 Stephenson Parkway Norman, OK 73019-5251 Office: (405)325-1126 lmtho...@ou.edu<mailto:lmtho...@ou.edu> http://www.ou.edu/structuralbiology/cobre-core-facilities/mcl<http://www.ou.edu/structuralbiology/cobre-core-facilities/mcl> ________________________________ To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1<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/
