THEORY OF THE RESPONSE BY DNA IN SOLUTION TO MICROWAVE ILLUMINATION
Abstract
Recent studies by Edwards, Davis, Swicord, and Saffer have indicated resonant absorption of microwave radiation by DNA in solution. Previous theoretical calculations had indicated such resonances should be overdamped. We present a more realistic model that provides a parameterization 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 parameterization indicates that the bound layers ability to transmit shear must be greatly reduced. 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. We have then taken this model and calculated the dependence of the resonant absorption upon temperature and bulk salt concentration. Surprisingly, no effect is observed. The absorption spectrum turns out to be invariant with respect to reasonable variations of most of the bulk solution properties. The two quantities that do affect the spectrum are the hydration layer relaxation time and the viscosity as it appears in the hydration layer binding. These two effects, however, cancel as they vary with temperature, leaving only the bond reduction parameter as a source of temperature or salt dependence. This could make the measurement of the temperature and salt concentration dependence an important tool for studying the hydration layer as well as an important check on any forthcoming theories of the bond reduction parameter.
Degree
Ph.D.
Subject Area
Biophysics
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