On Tue, Sep 27, 2011 at 11:16 AM, Yuri Pompeu <yuri.pom...@ufl.edu> wrote:
> I have a 2.3A data set that could be scaled in C 2 2 21 and P 1 21 1 > Intensity statistics tests indicate twinning (pseudo-merohedral h,-k,-h-l > in P 1 21 1) > I find a good MR solution and when I try to refine it with the twin law I > get fairly good maps and decent Rs 21-28%. I can see features tha were not > in the search model > Which leads me to think that this a valid solution. The one thing that > bothers me however is the fact that my beta angle in P 1 21 1 is 104 (not > close to 90) and that the geometry gets worse after refinement? > I've seen this before - the conventions for the C2221 and P21 unit cells are very different, so even if beta=104 in P21, the equivalent C2221 cell can still have all angles equal to 90. And you can definitely have pseudo-merohedral twinning in these circumstances (I did too - PDB ID 3ori). The problem with geometry is a separate issue - probably the automatic weighting not working properly, or an improper fixed weight. -Nat
