Theoretical analysis of low-lying vibrational modes of free canonical 2-deoxyribonucleosides

The low-lying vibrational mode frequencies of 2-deoxyribonucleosides (DNs) below 200 cm(-1) were analyzed using the density functional theory, Three types of vibrational modes of DNs were observed: the motion of sugar and base with respect to each other as almost rigid fragments; the modes localized within the sugar or base fragments; and the collective vibrations involving deformation of both the sugar and the base. These modes clearly differ by order and frequencies. The population of the ground and excited vibrational levels was estimated. These values indicate that only 15-27% of the molecules possess a geometry close to equilibrium at every moment in time. (C) 2000 Elsevier Science B.V. All rights reserved.