Comparative current-voltage characteristics of nicked and repaired λ-DNA

We report on current-voltage characteristics obtained at room temperature on lambda-DNA molecules, modified at both ends with disulfide groups and spanning Au electrodes. A comparison is drawn between the characteristics of the lambda-DNA, which after modification features a gap between 3' and 5' sites (nicked DNA), and lambda-DNA where this gap has been ligated (repaired DNA). The repaired DNA double helices show a close-to-linear current-voltage characteristic, and a dc conductivity estimated at similar to1x10(-3) S cm(-1). In contrast, the nicked DNA shows pronouncedly nonlinear and rectifying behavior, with a conductivity gap of similar to3 eV. The low-field conductivity of the nicked DNA is approximately a factor 20 lower than the repaired DNA's conductivity. (C) 2003 American Institute of Physics.