Hello, I'm working with evolutionary algorithms applied to protein-protein docking. I'd like to calculate de RMSD between the native complex and the complex achieved with my docking model. For that I was trying to make the superposition of the complexes using the match function through the Chimera command line. I called the function as: match #0 #1 and got the following message: Atoms in each selection must be in the same model I'd like to know what am I doing wrong, or if there is anyway other way to obtain the RMSD and the superposed complexes. I'm using the complex code PDB 1CHO. Thanks for any help, -- Helder Ken Shimo BSc in Biomedical Informatics (University of São Paulo - Brazil) MSc candidate in Bioinformatics (University of São Paulo - Brazil) -- "When I get sad, I stop being sad and be awesome instead." (Neil Patrick Harris as Barney Stinson)