Hi, <br>I am refining a low resolution data. According to sigma vs. resolution, my resolution is 4.7A. Because there are four identical molecular per asymetric unit, I can use positional refinement. There are about 65% alpha-helices in the structure, so I want to use secondary structure restrain. Does phenix has this restrain in the refinement? I am using Phenix-1.4 version. <br>