Hi all, I am trying to generate a helical trimer from the monomer pdb around a central double-stranded RNA. The rise and twist are 46 A and 74.0 deg respectively. I opened my monomer pdb in chimera *(Screenshot-0)* and used the following command to generate an axis around the central RNA double helix: *define axis #0:.X,.Y* where X and Y are the chain IDs for the 2 RNA strands This command helped me generate an axis named *a1* along the RNA duplex *(Screenshot-1)*. Now I want to generate a helical trimer along the RNA duplex with rise=46A and twist=74deg. For this I used the command: *sym #0 group H,46,74,3 axis a1* However, it is not placing the symmetric copies around axis a1 but around a distant axis *(Screenshot-2)*. I am not sure how to generate the helical trimer along the a1 axis. Any help in this regard would be appreciated. Thanks. -Sadeem -- :-)
