Conductivity and Thickness of DNAs

Debates about conductivity of DNAs have been recently renewed due to contradictory results of direct measurements by use of electrical contacts to molecules. In several works it was discovered that double-stranded (ds)DNAs are conductors: metals or semiconductors [1-6]. However in other works [7] the absence of DNAs conductivity has been observed even for the molecules with ordered base pairs structure. Here we show that the absence of conductivity is caused by a very large compression deformation of DNAs. Thickness of such compressed DNAs is 2-4 times less than the diameter (about 2nm) of native Watson-Crick B-DNA.