Hi, I’ve used align #2/X:1 @CA,O,C,N to #1/X:1 @CA,O,C,N align #3/X:1 @CA,O,C,N to #1/X:1 @CA,O,C,N align #4/X:1 @CA,O,C,N to #1/X:1 @CA,O,C,N … to align #2 molecule against #1 molecule with backbone atoms #3 molecule against #1 molecule with backbone atoms #4 molecule against #1 molecule with backbone atoms etc… However, how can I align all rest molecules (e.g. #2~#100) against #1 molecule with backbone atoms at once in chimeraX? I’ve used align all toAtoms #1 matchAtomNames true align all toAtoms #1 matchNumbering true to align all molecules to #1 molecule at once. However, with this command, I cannot specify to use backbone atoms (e.g. CA,O,C,N) only when aligning. I think that there should a 1 line command that aligns all molecules with specific atoms only or there is chimeraX equivalent python script as from chimera import runCommand as rc # use 'rc' as shorthand for runCommand from chimera import replyobj # for emitting status messages Best, Doo Nam