Judging from the gallery and videos, the Graphite – LifeExplorer is a great tool to model protein and DNA :
The Graphite-LifeExplorer modeling tool to build 3D molecular assemblies of proteins and DNA from Protein Database (PDB) files. Atomic DNA can be modeled from scratch or reconstructed from simulation.
I didn’t get the Mac-Version to work on my machine (Mac OS X 10.6.8) it works only for OS X 10.7.+ (got it running on 10.7.3) – it’s definitely worth keeping an eye on:
shared by Damien Larivière via LinkedIn/Molecular Modeling in Life Sciences.