Hello, I am having difficulty using Phenix to build and refine a DNA duplex. The issue is that my asymmetric unit consists of one protein monomer bound to DNA, but the protein is a dimer and the DNA is not palindromic, so each monomer is bound to a different sequence of DNA. As such, the density for the two different DNA half-sites is averaged out in the asymmetric unit. I have tried to place two duplexes directly on top of one another, each with 0.5 occupancy, and then refine. But I have noticed two problems. The first is that when xyz refinement is off, and I look at the output files, the density for DNA is awfully green, as if there were only *one* helix with 0.5 occupancy there. The other problem I noticed is that when I turn xyz refinement on, and look at the output files, one of the two half-sites gets moved several angtroms, so that it is in a region that generally has no density. I expect that, if done properly, the backbone of both half-site DNAs ought not to move. Any advice would be greatly appreciated. Thanks, Bryan Schmidt