Direct conductance measurements of short single DNA molecules in dry conditions.

We present a study of electronic transport in short (12-base-pair) DNA duplexes covalently bonded (via thiol groups) to two gold electrodes obtained by a mechanically controllable break junction (MCJB) technique in dry conditions. A large number of DNA junctions have been repeatedly formed in order to obtain a conductance histogram that reveals a peak which corresponds to the conductance of a single DNA molecule. We observed that the conductivity of a DNA increases upon increasing the content of G:C base pairs in the duplex. With our method we are able to obtain a reliable value of a single DNA conductance and subsequently measure its current–voltage (I–V) characteristics. In contrast to the electronic transport measurements performed with long DNA sequences (hundreds of base pairs) where the obtained conductance values vary a lot with environmental conditions, our values obtained for the short DNA sequences are consistent with the values reported for comparable sequences in aqueous solution.