Dear Ambrose, what I usually do is to detwin the <I>, I(+) and I(-) separately with the program DETWIN by renaming them to IMEAN and after detwinning gathering them together under their original names. I run then TRUNCATE after de-twinning. I've appendend a script for de-twinning anomalous data starting from a scalepack file. In my limited experience, a twin-fraction of 33% is still rather high meaning that the data are heavily manipulated in the detwinning process which might lead to a data deterioration. A crucial step is the proper estimation of the twin fraction. I've made good experiences with Todd Yeates's Twin Server (http://www.doe-mbi.ucla.edu/Services/Twinning/) and with the Britten-plot in the CCP4 program DETWIN (there, the twin fraction is the point where the number of negative intensities after de-twinning starts steeply to increase). Good luck, Dirk Kostrewa. ***************************************************** Dirk Kostrewa Paul Scherrer Institut e-mail: dirk.kostrewa@psi.ch Life Sciences phone: +41-56-310-4722 OSRA/007 fax: +41-56-310-4556 CH-5232 Villigen PSI WWW: http://www.sb.psi.ch Switzerland ***************************************************** > -----Original Message----- > From: owner-ccp4bb@dl.ac.uk [mailto:owner-ccp4bb@dl.ac.uk]On Behalf Of > Ambrose R Cole > Sent: Donnerstag, 13. September 2001 16:04 > To: ccp4bb@dl.ac.uk > Subject: [ccp4bb]: detwinning anomalous data > > > *** For details on how to be removed from this list visit the *** > *** CCP4 home page http://www.ccp4.ac.uk *** > > I have been having lots of trouble with 50% twinning for a Se-met > derivative that I am working on. Recently I have collected a data set > which appears to be less twinned (33%). I would like to attempt to detwin > this data set but keep the anomalous signal. Is it a good idea to > seperate the F+ and F-, detwin and then join them back together if so how > do I join them back together to create a normal mtz file with FP, DANO > etc. > > any help would be greatly appreciated > thanks > Ambrose >
scalepack_detwin_truncate_anomalous.sh