Characterization of Oriented Thin Films of DNA

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Deoxyribonucleic acids (DNAs) are important as a source of biological information depending on their base sequences. DNA is also interesting as a molecular material that shows a long rod-like duplex structure with base-pair stacking-the base separation is 3.4 Å while the diameter of the duplex is about 20 Å, therefore appears to be a good candidate for one-dimensional energy transfer and conduction along the p electron clouds of the stacked bases.In this report, we summarize preparations of DNA-aligned Langmuir-Blodgett (LB) film and its anisotropic electron conductivity.The DNA aligned film was prepared as follows. On the aqueous solution of DNA from Salmon testes and intercalator (ethidium bromide), Langmuir monolayer of cationic lipids were prepared, and DNA-lipid complexes were transferred on a substrate. It was confirmed by polarized absorption spectra that DNA strands aligned along a dipping direction.The dc conductivity was measured by using an ammeter in atmosphere. When the DNA film was put on the comb-shaped electrode as DNA strands aligned perpendicularly to two Au electrodes, a large ohmic current was observed that increased linearly with increasing the applied voltage up to 0.1 V. On the contrary, when the film was put as DNA strands aligned parallelly to two electrodes, electric current was hardly observed even at the voltage of 0.1 v.