Hi Gea-Ny, Elaine's comments are right. But there might be an easier way to generate the potassium channel tetramer. If the tetramer appears in the crystal from which the monomer structure was obtained you can use the Chimera Unit Cell or Multiscale tools to get it. Generating the unit cell only requires the CRYST1 PDB record, a one line record describing the crystal symmetry group and unit cell parameters. That line appears in all files from the PDB web site. If the tetramer is not found in the crystal then it may be a non-trivial task to determine the correct 4 matrices to build a tetramer from a monomer. If your K channel monomer is deposited at the PDB I can investigate if you send me the PDB identifier. Sorry for the delayed reply. I was on vacation and at a workshop the past week and a half. Tom