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Temperature and concentration behavior of anomalous microwave resonances in DNA
Author(s) -
Davis M. E.,
Van Zandt L. L.
Publication year - 1989
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360280808
Subject(s) - polymer , chemistry , absorption (acoustics) , counterion , microwave , hydrogen bond , molecule , chemical physics , solvent , relaxation (psychology) , ion , materials science , organic chemistry , social psychology , psychology , physics , quantum mechanics , composite material
We have calculated the expected absorption of microwave radiation in the gigaHertz frequency range by fixed‐length DNA polymer molecules dissolved in saline solution. While the effects of counterions and solvent dynamics have been accounted for in detail, the features of the absorption are completely dominated by the interaction between the charged polymer and the so‐called first hydration layer, that is, the nearest layer of solvent water molecules not actually bonded to the polymer. The relevant parameters of the interaction are the strength of the water‐to‐polymer coupling and the average persistence time of the individual water‐to‐polymer bonds. These are presumably hydrogen bonds to the oxygen atoms of the backbone phosphate structure. Using a given parameterization we can obtain the structured absorption corresponding to compressional wave phonon excitations on the polymer, “organ pipe” modes, such as have been claimed to be seen by Edwards, Davis, Swicord, and Saffer. While further studies have not confirmed these resonances, at some frequency and hydration these modes must become visible because of the high relaxation time measured by Lindsay, the existence of the resonances in relatively dry fibers and films of DNA, and the existence of underdamped modes in the ir spectrum of DNA in solution. We have examined the effects of varying slat concentration and the system temperature. In both cases the effects are virtually nil, in the former because of the Manning condensation phenomenon that preserves a remarkably constant polymer environment over a wide range of bulk ionic strength, and in the latter case because of a fortuitous competition between effects of bulk viscosity and persistence time changes with temperature. Hence any effects seen in the experimental variation of temperature or salinity could be wholly attributed to their modification of the hydration layer properties.