Interpretation of DNA vibration modes: III--The behaviour of the sugar pucker vibration modes as a function of its pseudorotation parameters.

A systematic study of the sugar pucker characteristic vibration modes as a function of its geometrical conformations, has been performed. The present investigation is based on the Wilson GF method and a non-redundant valence force field. The calculated results allow to assign the modes arising mainly from the sugar motions and present in quasi whole vibrational spectra related to the right or left-handed double-helices (i.e., 1050 cm-1, 960 cm-1 and 890 cm-1). Moreover, the conformation dependent modes as those at 860 cm-1 and around 810 cm-1 (A form) as well as the one located around 830 cm-1 (B form) are interpreted by the present investigation. The possibility of the interaction of the latter modes with the phosphate group motions along the DNA double-helical chains are also discussed.