Conduction in nucleic acid components

Abstract

IN a recent paper1 DNA was shown to possess a small semiconductivity in the dry state, the specific conductivity following the equation: with Δε Combining double low line 2.42 eV, log 10(κ0, Ω-1cm-1) Combining double low line 3.4. It was suggested that the conductivity was associated with the π-electron overlap of the paired bases, adenine-thymine, and guanine-cytosine. In the Crick and Watson double-helix for DNA structure these base pairs are arranged one on top of the other, with an interplane spacing of 3.4 Å, similar to that found in graphite2. A similar result was found for the electrical conductivity of RNA, which may now be related to its high content of double-helix structure3. We have examined the solid-state electrical conductivity of some of the component structures of the nucleic acid, using d.c. with the polycrystalline specimen compressed between nickel electrodes at 80 kg cm-2, in a vacuum of 10-6 mm mercury. The bases adenine, thymine, guanine, cytosine and uracil were first examined. These gave very low conductivities, around 10 -15 Ω-1cm-1 at 400°K, but sublimation (even in a nitrogen atmosphere) and thermal decomposition precluded the establishment of accurate Δε values. The nucleosides had conductivities of 10-11-10-13 Ω-1cm -1 and the nucleotides 10-7-10-12 Ω-1cm-1 at 400°K. The results are listed in Table 1. © 1963 Nature Publishing Group.