Chimera 1.8 on Windows I have been trying to align (superimpose) models based on a specific conserved region. Unfortunately Chimera doesn't seem to do what the documentation claims it does. I run (example): match #0:5-15@CA,20-30@CA #1: 5-15@CA,20-30@CA and get an RMSD calculation (more on this below), but no movement of the model occurs. I specify 'move true show true' as options. Still no movement but I have a transformation matrix. Unfortunately this is not in a form that can be understood by Transform Coordinates. How do I persuade my structures to superimpose on the specific atoms? The RMSD calculation appears to be broken. If I take the command rmsd #0:5-15@CA,20-30@CA #1: 5-15@CA,20-30@CA then I will get a number If I then run rmsd #0:5-15@CA,20-30@CA #1: 5-15@CA,21-31@CA I get exactly the same number. In fact, if I specify atom sets of different sizes (as long as it is not the first block) then I continue to get exactly the same number rmsd #0:5-15@CA,20-30@CA #1: 5-15@CA,20-35@CA This should fail but doesn't Have I completely misunderstood what Chimera should be doing here? ..d The University of Dundee is a registered Scottish Charity, No: SC015096