Nonlinear current-voltage characteristics measured across circular deoxyribonucleic acid (DNA) molecule bundles

We measured current-voltage characteristics of circular deoxyribonucleic acid (DNA) bundle samples embedded in a water mantle lying on a nylon porous membrane between vacuum-evaporated gold electrodes. The nonlinear behavior observed at room temperature on samples of different molecular sizes and variable concentration was interpreted as a long-range conduction mechanism that takes place by means of charge hopping through the network of molecules. A tunneling process acting as an additional transport channel inside single molecules between energetically appropriate bases was inferred. Our data also suggest at low bias a thermionic emission mechanism by means of which the charges move from one electrode, overcoming a potential barrier. Characteristic energies involved in the transport were reproducibly measured.