Electron-molecular-vibration coupling for small polarons in DNAs.

Within a tight-binding electron-phonon interacting model, we calculated the spectrally resolved polaron binding energy between electrons and phonons and between holes and phonons on poly(dA).poly(dT) and poly(dG).poly(dC).Poly(dA).Poly(dT) is a DNA where one single strand consists only of adenine(A) and the other single strand consists only of thymine(T), while Poly(dG).Poly(dC) is a DNA where one single strand consist only of guanine(G) and the other of cytosine(C). We found that the polaron binding energies of poly(dA).poly(dT) were larger than those of poly(dG).poly(dC), and that the polaron binding energy and the electrical conductance were strongly temperature dependent. These findings agree well with the current experimental data. We concluded that small polaron hopping occurs by a conduction mechanism on the DNA molecules examined.