ON A SIMPLE-MODEL OF LOW-FREQUENCY VIBRATIONS IN DNA MACROMOLECULES

A simple quasi-continuity model of low-frequency dynamics of DNA macro molecules is presented. The model is based on the phenomenological the ory by Volkov and Kosevich (J. Biomol. Struct. Dyn. 8, 1069 (1991)). W e propose improvements to their theory by correcting the model energy and corresponding equations of motion, recalculating the model DNA par ameters, and estimating the effects of hydration and counterion bindin g on the masses of DNA subunits. Comparing the calculated low-frequenc y vibration spectrum and the results of classical Raman scattering exp eriments from the literature, the values for the model force constants are determined. These values differ significantly from the estimation s made by Volkov and Kosevich. A good quantitative agreement with expe riment can be obtained both for the case when the ''25 cm(-1) mode'' i s an external one, and when it is considered as an intrahelical mode. Problems connected with the qualitative assignments of the calculated and experimentally observed modes are discussed.