First - you probably have the best solution you can hope for - Rs of 27% & 33% are not great, but unlikely if you had a wrong answer.
A query though: t is surprising to have a pseudo translation if you expect one molecule in the asymmetry unit .. an you elborate a bit on that? Is there a good reason to try to get more information from this 3A twinned data, if the same structure is already solved. If there is a good reason then it is worth persisting, but it will be difficult Eleanor On 5 September 2013 13:09, Ashu Kumar <kumar1980a...@gmail.com> wrote: > 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 > >
