Hi Ina,

I try to refine a crystal structure of a protein - inhibitor complex. The

protein is a homodimer and the two molecules have a crystallographic symmetry. The space group is P6122. The symmetric inhibitor binds symmetrically to the protein so that I refine the half of it. The core of the inhibitor is a five-membered ring with a nitrogen lying directly on the axis of symmetry. I achieved to refine this by setting the occupancy to 1.0. And now, here is my problem: Two C atoms of this ring system are bound across the symmetry axis - how could I include this in the refinement? Is there any possibility to generate restraints to the other part of the inhibitor (of the symmetry equivalent)??

It is possible but cumbersome. With a reasonably recent version of phenix (dev-268 or later) it is much simpler to have the entire inhibitor in the pdb file, with occupancy 0.5. All the rest is taken care of automatically. Ralf P.S.: http://www.phenix-online.org/pipermail/phenixbb/2009-December/003070.html