Electron-phonon coupling in DNA: a systematic study

The coupling of all twelve possible conformational modes of DNA duplexes and four pair-wise correlations among them to positive charge (hole) motion through these biopolymers has been systematically analysed in regular homogeneous B-DNA trimers and tetramers of adenosine-thymidine (AT) and guanosine-cytidine (GC) Watson-Crick pairs using PM3 semiempirical quantum chemistry. Of these only five modes have been found to be most strongly coupled to the electron motion in DNA, namely stretching of H-bonding both in AT and GC, correlated Buckle-Rise and Stagger-Tilt motions in GC and correlated Shear-Twist motion in AT. The parameters for the corresponding polaronic Hamiltonians have been estimated. The nature of these DNA polarons is discussed taking into account the relevant experimental results currently available.