Duality of maximal-torsion and close-packing in double helices

Abstract

It is suggested that there is an interesting transition in double helices. The transition is between a helix, which has maximal torsion for the constituting helical strands, and a double helix which is nearly optimally packed illustrated by corresponding dual points on the rope curve. The possible physical relevance for denaturation and renaturation of DNA is discussed.