Dear Uli, It seems that you are dealing with psued-twinning when cell do not overlap after rotation with twin operator. In these case what is in one resolution on one of the orientation becomes another resolution in another orientation of crystals
In short:. You have an operator R that relates two orientation of the crystal. If R does not convert cell to itself completely then resolution of twin related reflections h' and h h' = Rh will be different. It usually means that in your images spots are split at higher resolution. If you have not integrated those spots as one at higher resolution then refinement may not be optimal. These cases needs to be considered as multiple orientation of the same crystal. I think MOSFLM should be able to integrate them as several cells. However refmac is not completely ready to deal with these cases as optimally as it should. I hope it clears things a bit. Cheers, Garib On 22 May 2014, at 15:48, [email protected] <[email protected]> wrote: > Dear colleagues, > > I am in the process of refining a P2(1) structure that is marked by Scala as > twinned (L-test etc.) with a twinning fraction of ca. 0.2. I am still working > on the twinning problem, so no more details about this. But what puzzles me > right now is that, if I feed the data with a max. resolution of 1.95 A into > Refmac with the "twin" refinement option on, it recognizes the resolution > cut-off at first, but then uses a new cut-off of 1.88 A in the first ( and > all subsequent) refinement cycles. Since there are no data at this > resolution, this seems to screw up the calculation of R-values at high > resolution and it reports for them zero-values in the co-ordinate header. > Without twin refinement, the max. resolution stays at 1.95 A (but the final > stats are worse, of course). > > Is this a bug or am I missing here something? > > Thanks in advance, and I am happy to send log files or my precious data if > necessary. > > Cheers, > > Uli > > --------------------------------------------------------------------------- > dr ulrich gohlke > staff scientist - macromolecular structure and interaction > max-delbrück-center for molecular medicine (mdc) > > +49 30 9406 - 2725 (w) > +49 30 9406 - 2548 (fax) > [email protected] > > http://www.mdc-berlin.de/en/research/research_teams/macromolecular_structure_and_interaction/ Dr Garib N Murshudov MRC-LMB Francis Crick Avenue Cambridge CB2 0QH UK Web http://www.mrc-lmb.cam.ac.uk, http://www2.mrc-lmb.cam.ac.uk/groups/murshudov/
