  We propose a model for DNA dynamics by introducing the helical structure
through twist deformation in analogy with the structure of helimagnet and
cholesteric liquid crystal system. The dynamics in this case is found to be
governed by the completely integrable sine-Gordon equation which admits
kink-antikink solitons with increased width representing a wide base pair
opening configuration in DNA. The results show that the helicity introduces a
length scale variation and thus provides a better representation of the base
pair opening in DNA.
