Modeling hole transfer in DNA oligonucleotides

Since its discovery, the ability of singly ionized DNA to provide long-range hole transport (HT) has attracted considerable interest. Apart from the biochemical implications connected with the oxidative damage of nucleic acids, long range HT makes DNA a potentially well-suited material for nanoelectronics, either by exploiting its self-assembling properties or by using it as the active component in nanocircuits. Theoretical simulations show that in short oligomers, consisting of two guanines separated by a bridge of up to three thymine bases, intrastrand hole tunnelling between guanines can occur on picosecond timescales, about three orders of magnitude faster than hole hopping, whereas interstrand charge transfer becomes faster in oligomers with longer bridges of four or five thymines. Tunnelling becomes extremely slow in longer oligomers, containing more guanine sites in the strand, because charge can bounce among them. Our results are able to reconcile conflicting experimental results [3], showing the great complexity of charge transport in molecular systems.