Intensities of DNA ion-phosphate modes in the low-frequency Raman spectra
Bogolyubov Institute for Theoretical Physics, NAS of Ukraine, 14-b Metrologichna St., 03680, Kiev, Ukraine
Revised: 10 November 2009
Published online: 12 February 2010
The Raman intensities of counterion vibrations with respect to the phosphate groups of the double-helix backbone (ion-phosphate modes) in the low-frequency spectra (< 200 cm-1) of B -DNA with different alkali metal counterions have been calculated using the model for DNA conformational vibrations and the valence-optic approach. The results have showed that the spectra of DNA with heavy counterions ( Rb+ and Cs+ differ from the spectra of DNA with light counterions ( Na+ and K+ . The calculated spectra of DNA with heavy counterions are characterized by intensive modes of ion-phosphate vibrations that form one united band near 115cm-1. Ion-phosphate modes in the spectra of DNA with light counterions are characterized by higher frequencies (near 180cm-1) and much lower intensity. Our calculations explain why the modes of ion-phosphate vibrations are observed in Cs-DNA spectra rather than in Na-DNA. The determined sensitivity of the intensities of DNA low-frequency spectra to the counterion type proves the existence of the ion-phosphate modes.
© EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg, 2010