Response of the electric conductivity of double-stranded DNA on moderate mechanical stretching stresses

The response of charge transport in double-stranded DNA to mechanical pulling has been studied with a multiscale computational method using classical molecular dynamics simulation, approximative density-functional theory calculations and the Landauer-Büttiker theory. The effect depends on the exact nucleobase sequence notably, and this is explained in terms of structural changes of DNA upon stretching. The results of recent single-molecule experiments are interpreted on the basis of current results. Further, recommendations for the design of DNA sequences for nanoelectronic applications are formulated.

Figure 1

The central seven base pairs of the DNA oligomer GG being stretched up to the additional extension of ca. 25$\%$ of the free length by pulling at the 3${}^{\prime }$ ends. The backbones are depicted as ribbons, with color coding the conformation: blue (dark), helical, B-like dsDNA; yellow (light), ladderlike S-DNA. The helical dsDNA structure passes to a ladderlike one, gradually.

Figure 2

Hole transport efficiency expressed as electric current at high voltage through the studied DNA devices depending on the end-to-end distance of the DNA strand. The distance is given relative to the equilibrium length of the respective DNA oligomer in a free MD simulation.

Figure 3

Electronic coupling (T${}_{ij}$) and value of the helical parameter slide for the individual base-pair steps for the sequences GG (top) and GT (center). Mean values for ensembles generated by MD simulations are presented; see Table for the designation of base-pair steps. (Bottom) Meaning of the helical parameter slide; every box depicts one nucleobase.

Figure 4

Schematic depiction of the change of relative orientation of purine nucleobases (G, A) upon the onset of overstretched, ladderlike structure in a dsDNA fragment.