Dear all,
I am trying to solve the structure of a protein at ~3 A. Though the
structure is already solved in a different space group. I thought it would
be a straight forward MR problem. But there are a couple of problems:
The possible point group is P3 (2 molecules / asu) and pointless and
phenix.xtriage predicted it to be P321 ( 1 molecule /asu). But it shows 37%
twinning with P3 whereas twinning is 0.055 % in P321. Several attempts to
get a sensible MR solution, in either of the space groups, failed. R and
Rfree were always in the range of 35-40 %. In both the cases there is a
pseudotranslation of ~17%.
Even different runs of the same inputs gave different solutions on
multiple trials. After many trials, molrep gave one solution in P3 with 2
molecules/asu which when refined in Phaser with twinning corrections gave
R and Rfree of 0.27 and 0.33 respectively. The map looks good and there is
nothing really to do in terms of model-building.
While my attempts to get better dataset are ON, I was wondering how to
ensure that the solution/symmetry which I got are correct (or find out that
they are wrong.) and also what next with this data sets in either cases to
reach to a correct model?
Any suggestion would be highly appreciated.
Thanks
Ashu
