Hello again, You guys were so helpful last time I figured I'd just ask for help again! I'm trying to do something that I know is a feature in PyMol but I'm not sure if it is a feature in ChimeraX (yet). In PyMol, there is a function to pair fit over specific atoms between two different structures. I have tried using the Matchmaker tool in ChimeraX to do this, but I think the dilemma is I'm trying to align the protein relative to the position of specific atoms in a heme cofactor across two different structures and that isn't something in the primary sequence of the protein. I also could just be doing something wrong in the matchmaker process. Do you know if there is an easy way to accomplish this in ChimeraX? Best regards, Rachael Coleman -- *Rachael E. Coleman* PhD Candidate, Lancaster Group Department of Chemistry and Chemical Biology Cornell University Ithaca, NY 14853 Pronouns: She, her, hers