Abstract
We study the influence of viscosity on DNA dynamics. By employing the nonlinear Peyrard–Bishop–Dauxois (PBD) model, it is shown that the DNA dynamics can be explained by a solution of a complex nonlinear Schrödinger equation (CNLSE). This is the nonlinear Schrödinger equation (NLSE) with a nonlinear parameter being a complex number. We compare real and imaginary parts of this nonlinear parameter and show that the latter one is negligible, which means that the CNLSE should be solved numerically.