Dresden 2006 – scientific programme

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AKB: Biologische Physik

AKB 40: Poster Session II

AKB 40.15: Poster

Wednesday, March 29, 2006, 16:30–19:30, P3

Conductivity of unordered denatured and hybridized DNA — •Thomas Kleine-Ostmann¹, Christian Jördens¹, Kai Baaske¹, Thomas Weimann², Martin Hrabe de Angelis³, and Martin Koch¹ — ¹Inst. f. Hochfrequenztechnik, Schleinitzstr. 22, 38106 Braunschweig — ²Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig — ³GSF National Research Center for Environment and Health, Ingolstädter Landstr. 1, 85764 Neuherberg

The electronic properties of DNA remain highly controversial. Depending on the technique and the experimental conditions, a variety of - sometimes contradictory - results have been obtained. They are of paramount importance for two visionary technologies: self-assembled nanoelectronics and marker-free gene tests. Here, we report on the conductivity of natural DNA under ambient conditions. We examined both single-stranded and double-stranded herring DNA in buffer solution that consists of 120-3000 nucleotides. It was spotted and dried on Au nanocontacts deposited on oxidized Si with a gap size of 100 nm. I-V curves are obtained in a sealed measurement chamber that allows for the adjustment of the ambient relative humidity in a wide range from 10 to 100 percent. We find an exponential humidity dependence of the conductivity that is identical for single- and double-stranded DNA within the measurement accuracy. While the small conductivity of dry DNA is comparable to that of a large band-gap semiconductor, we attribute the increased conductivity of DNA at high humidity levels to water molecules accumulated at the phosphate backbone. We observe s-shaped I-V curves that can be well explained by the dissociation of water attached to the DNA molecules.