Hi Fermat,
Sorry for the delay. I was away at a wedding with no internet access from Fri-Mon.
One of my team members has requested a little change, I hope its not too big of a deal to see ...
He would like to see a sample with more of a differentiation between the top and bottom strands on the helix.
See:
http://imgur.com/HVcWyWfOr maybe you have a better idea on how to show the 3D nature of the helix?