Electrical conductivity of double stranded DNA measured with ac impedance spectroscopy

Abstract

The electrical conductivity of double stranded DNA is investigated with ac impedance spectroscopy. Atomic force microscopy is used to provide images of the DNA molecules stretched over some gap electrodes through a flow cell. More stretched DNA molecules result in smaller charge-transfer resistances in the ac impedance spectra. The DNA molecules stretched across the electrode gaps can be degraded with the enzyme DNase, which generates larger charge-transfer resistances or results in capacitive behavior. The distorted DNA molecules filled in the electrode gaps rather than stretched over the gap electrodes do not exhibit the electrical conduction in the ac impedance spectra. The present work suggests the double stranded DNA to be a one-dimensional semiconductor. It also suggests that the ac impedance spectroscopy may be a more effective method than a dc one to measure the electrical conduction of double stranded DNA. The electrical and ionic conductivities of DNA molecules are extensively discussed.