Large amplitude of the internal motion of DNA immersed in bio-fluid

The interaction between large internal motion of DNA surrounded by bio-fluid is investigated. The phenomenon is modelled using the relativistic Navier-Stokes lagrangian describing the bio-fluid coupled to the standard Klein-Gordon lagrangian describing the DNA. It is shown that the equation of motion at non-relativistic limit, v << c, reproduces the well-known Sine-Gordon equation. The effect of the interaction in a single soliton solution is also given and discussed.