If I understand correctly, the only difference between "mFo" and "Fo" map will be weighting in different resolution shells according to figure-of-merit. While this will presumably downweigh the less reliable resolution shells, it will hardly make up for the heavy model bias. The reason you see the missing region in (2mFo-DFc) map is because it is effectively the sum of model map (mFo) which shows you the parts of the model you have already placed and difference map (mFo-DFc) which shows you the regions which are still missing.
On Tue, 2010-08-31 at 15:20 -0400, zhan...@umbc.edu wrote: > Actually I cut a small domain from the well-defined structure (just for a > test). The missing part showed in 2mFo-DFc map but not in both mFo and Fo > maps, and the mFo and Fo maps are so close so that I wonder whether figure > of merit generated by SIGMAA helps or not in this situation... > > Best Regards, Hailiang > > > On Tue, 2010-08-31 at 13:15 -0400, Hailiang Zhang wrote: > >> Is the difference > >> between mFo and Fo maps supposed to be very small? > > > > For an essentially correct model, yes. The major advantage of (2mFo-DFc) > > maps is suppression of model bias, so if you don't see much difference > > then your model is very well refined. For illustration, introduce a > > systematic error on purpose and see which map gives you better result. > > > > -- > > "I'd jump in myself, if I weren't so good at whistling." > > Julian, King of Lemurs > > > > > >
