Yes, Phenix default output (for twinned data) is detwinned, like the one from Shelxl; didn't know for the new Refmac twin option - but I understand from this posting and Garib's that it also detwins if the twin option is used ... So considering that the Shelxl-derived density looked bad, I definitely agree with Tassos (and apparently didn't make that point clear enough) that other reasons for bad density than twinning have to be considered ...
Best Clemens -----Ursprüngliche Nachricht----- Von: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] Im Auftrag von Eleanor Dodson Gesendet: Monday, March 16, 2009 12:52 PM An: CCP4BB@JISCMAIL.AC.UK Betreff: Re: [ccp4bb] AW: [ccp4bb] Twinned data and maps But dont all twinned refinement programs output detwinned terms for a map? Certainly REFMAC and SHELX do. Eleanor Clemens Steegborn wrote: > Hi Walter, > > You should definitely detwin data for map calculation if you have a > significant twinning fraction (and only for maps; keep using the twinned > data set for refinement). We use the CCP4 program detwin. BUT if Shelxl > gives bad density, maybe that's simply what you have, a bad density map - > because output from Shelx is already detwinned! > BTW, we observed that different programs handled different cases differently > well; I would suggest ALWAYS to try more than one program, and also to try > Phenix ... > > Best > Clemens > > > -----Ursprüngliche Nachricht----- > Von: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] Im Auftrag von > Walter Kim > Gesendet: Monday, March 16, 2009 7:22 AM > An: CCP4BB@JISCMAIL.AC.UK > Betreff: [ccp4bb] Twinned data and maps > > Hi again, > > Thanks for your insight into refinement tools for twinned data. I have a > couple of twinned data sets that are nearly perfectly pseudomerohedrally > twinned. I've begun to refine my data in Refmac5 (using the automated twin > refinement), CNS (using the twin inputs) and Shelxl; I'm testing out the > different refinement programs to evaluate the best strategy for the > refinement. However, I would like to start making maps. > > 1. Refmac5 - outputs an mtz that is model-biased > 2. CNS - maps made via model_map_twin.inp are poor > 3. Shelxl - the maps generated in coot from the.fcf file are poor > > Are there better ways to make cleaner maps with my twinnned data that are > less model-biased that I can try to build into? Should I detwin the data and > make maps from that (but continue to refine against the twinned data)? > > Thanks, > Walter > > > >
