Dear all, I am working on a low resolution dataset (4.2 angstrom) of a multidomain complex. Using MR and density modification with NCS I obtained map in which I am extending/modifying my MR-models for the different domains. I tried to build the mainchain as a polyala model (extending on my MR-models) and then refined my new model in phenix.refine using torsion angle refinement. I have fourfold NCS and I think a this point it would be advantageous to use NCS-constraints instead of restraints. Is this possible in phenix? If I set the coordinate_sigma in de .def file to zero will this result in constrained NCS-refinement? ncs { restraint_group { reference=XXX selection=YYY coordinate_sigma=0.00 b_factor_weight=10 } Thank you very much for your advice, kind regards, Kenneth