I apologize in advance if this has been answered somewhere else, but I'm having trouble running the backrub program with non-canonical amino acids. Our designed protein includes a chromophore and I constructed a .params file that works with the fixbb application but I can't get backrub to recognize it. I tried renaming one of the atoms to act as a C-alpha for the pivot moves but it still doesn't work. I was just wondering if anyone knows how to get the .params files to work with backrub or if this is even the right was to recognize non-canonical amino acids. The chromophore doesn't even need to move at all during design, it just needs to be considered. Any help would be greatly appreciated!