  The conformational vibrations of Z-DNA with counterions are studied in
framework of phenomenological model developed. The structure of left-handed
double helix with counterions neutralizing the negatively charged phosphate
groups of DNA is considered as the ion-phosphate lattice. The frequencies and
Raman intensities for the modes of Z-DNA with Na+ and Mg2+ ions are calculated,
and the low-frequency Raman spectra are built. At the spectra range about the
frequency 150 cm-1 new mode of ion-phosphate vibrations is found, which
characterizes the vibrations of Mg2+ counterions. The results of our
calculations show that the intensities of Z-DNA modes are sensitive to the
concentration of magnesium counterions. The obtained results describe well the
experimental Raman spectra of Z-DNA.
