Try a lower symmetry, e.g. P21 or P1 with one or two octamers in the asymmetric unit (well, unit cell for P1), but you already know your packing so no problem solving it. It can sometimes be very subtle and your model refinement will be the most sensitive test for the correct space group - so don't be misled by seeming perfect scaling in orthorhombic.
Poul On 03/10/2010, at 04.56, Jack Russel wrote: > Hi all, > > I have collected a data at 2.9 Å and the solved the structure using phaser . > the space group comes to be P2 21 21. There are 4 molecules in Assymetric > unit and an octamer is generated according to the symmetry. But after > repeated rounds of rigid body refinement with REFMAC5 and model building with > coot the R factor had been struck at 40% and R free at 50%. > > So my first question is whether my solution after phaser is correct. And if > it is how can i lower the R factor and Rfree. > > The second question is it possible to have such a large difference between R > factor and R free. > > Thanks in advance > >
