> > R Rfree Fract > P6122 0.277 0.362 > P61 0.266 0.35 > P61 twin 0.177 0.219 0.494 > P3112 0.27 0.352 > P3112 k,h,-l 0.177 0.22 0.494 > P3112 -h,-k,l 0.177 0.22 0.494 > P3121 0.27 0.357 > P3121 -k,-h,-l 0.177 0.213 0.494 > P3121 -h,-k,l 0.177 0.213 0.494 > > It seems I have for second time in a year a tetartohedral twinning in the > space group P31.
I suggest that for all twin laws in each sg here you compute an R vs R statistics and see what you get. For that, you need to have both Fobs and Fcalc in the same file (which is easy enough using phenix.twin_map_utils, it outputs obs_and_calc.mtz). A susbequent run of xtriage where you will feed in both fobs and fcalc wil compute the rvsr stats. Use the reference to the paper by Lebedev Vagin & murshudov as a guideline to find out how to interpret these values. algebraic detwinning results in maps that are less biased, but with the twin fraction you describe, that is not possible. You could try having a look at gradient maps of the LSQ target on F as produced by phenix refine to see if it makes things better. HTH Peter
