Microwave response of DNA in solution: Theory

Recent studies by Edwards, Davis, Swicord, and Saffer have indicated resonant absorption of microwave radiation by DNA in solution. Previous theoretical calculations had indicated that such resonances should be overdamped. We present a more realistic model that provides a parametrization for the overcoming of the overdamping. The refinements include the electrically active nature of the solvent and the binding of the first hydration layer. Our results show that the hydration layer binding is the single most important aspect of the phenomenon. The parametrization indicates that the ability of bound layers to transmit shear must be greatly reduced. This is a behavior that can be qualitatively explained in terms of bond orientation by the structured water and reduced bond density for the DNA-water interface as opposed to corresponding surface in pure water. Conclusive results, however, await a discrete molecular modeling of the hydration layer binding.