Figure 1. Comparison of DNA and graphite structures.
Spacing between adjacent base pairs in DNA (3.4 Å) is similar to the planar spacing in graphite (z-direction). This close proximity of aromatic base-pairs allows for significant oribital overlap along the DNA helix, resulting in π-stacking of the DNA bases. The structural similarity between graphite, a known conductive material, and DNA was an initial clue to the conductivity of DNA. PDB file 3BSE (DNA).