Abstract
We have studied theoretically the movement of large molecular groups of DNA double helices in solution, which are driven by the electromagnetic field. The longitudinal vibration of nucleotides and the torsional movement of bases are taken into account at the same time. A set of coupled nonlinear partial differential equations has been established, and we have solved these equations by the method of perturbation. The result shows that there exists resonant absorption of microwave energy for both longitudinal and torsional modes. The resonant frequencies for the former and the latter are in the region of gigahertz and subterahertz, respectively. In addition to an nth-harmonic resonance at ωn, our theory also predicts a subharmonic resonance at ωn/2. The strength of the latter is proportional to l3, where l is the length of DNA. The necessary conditions to observe these resonances are also discussed.