BioBlender is a 3D modelling tool for Biologists, as the name suggest – it’s based 0n the popular open source 3D modelling/animation software “Blender”. So it’s kind of Blender optimized for drawing Biological stuffs (proteins molecules).
BioBlender is available for all-platforms. Visit official site for more options.
Download BioBlender for GNU/Linux (current version : 0.6)