[Chimera-users] representing 70s ribosome in ribbon

Hi, I am tring to show the full 70S ribosome structure (PDB id: 1GIX and 1GIY) in ribbon representation with EM experimental density together. These PDB data consist of backbone atoms only (single alpha carbon for each a.a and single phosphate for each nucleotide). Ribbon option does not generate any ribbon (due to the incomplete information in the PDB?). Is there any way to show this molecule in ribbon format? I assume that backbone atoms must be enough to generate ribbons. BGHan