Dear Petr, a map needs amplitudes and phases. In the case of the usual maps (2Fobs-Fcalc and Fobs-Fcalc) calculated for twinned data, one can either detwin the amplitudes, or take twinning into account in the Fcalc term.
When calculating the anomalous map, I believe that detwinning of anomalous differences would add a lot of noise. Nevertheless you could try the detwin program; in the best case you get a noisy anom map but with the ghost peaks suppressed ... not sure if this can be done in ccp4i2 . Taking twinning into account in the Fcalc term is not necessary since the Fcalc are not used in an anomalous map. So I guess the best way is just calculating the map as if the data were not twinned. You may get additional peaks at a height of 0.29/0.71 the height of the correct peaks (and this probably depends on whether the crystal symmetry has a rotation axis parallel to the twin axis). Probably I should have read Z. Dauter's "Twinned crystals and anomalous phasing" in Acta Cryst. (2003). D59, 2004-2016 before writing this ... Good luck, Kay On Tue, 29 Mar 2022 06:56:47 +0000, Petr Kolenko <petr.kole...@fjfi.cvut.cz> wrote: >Dear colleagues, >We have data from a twinned crystal (merohedral twinning with fraction of >0.71) for which we want to see the anomalous map. Could you please guide me >how to calculate it using the i2? Running refinement with REFMAC5 with >merohedral twinning does not allow simultaneous generation of anomalous maps. >Best regards, >Petr > >######################################################################## > >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/
