But wouldn't detwinning be problematic with nearly perfectly twinned data? I'll post my own question about separately to not hijack the thread...
On Mon, 2009-03-16 at 11:24 +0100, 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 -- Edwin Pozharski, PhD, Assistant Professor University of Maryland, Baltimore ---------------------------------------------- When the Way is forgotten duty and justice appear; Then knowledge and wisdom are born along with hypocrisy. When harmonious relationships dissolve then respect and devotion arise; When a nation falls to chaos then loyalty and patriotism are born. ------------------------------ / Lao Tse /
