Chapter 21 - Electronic transport and localization in short and long DNA

Abstract

Whether DNA conducts electric charges is the subject of various theoretical and experimental issues, intriguing to physicists and biologists alike. Electron transport in DNA is biologically important. A series of experimental and theoretical investigations were conducted and are reviewed in detail for both short DNA strands and longer ones with significant differences between specific DNA sequences, such as the periodic repetitions and aperiodic sequences of AT bases, λ-DNA, centromeric DNA, and promoter sequences as well as random-ATGC DNA. The results presented are preliminary results but indicate a marked difference in the nature of the electronic HOMO–LUMO (highest occupied molecular orbital) (HOMO) (lowest unoccupied molecular orbital) (LUMO) states for the periodic and aperiodic structures of duplex DNA. These results indicate that the HOMO–LUMO states for the periodic structure are quite extended. The concept of static localization in short DNA (Anderson localization) and for longer DNA sequences, diagonally disordered Anderson chain is discussed. The results discussed are consistent with previous results. It also discusses how transport properties differ between sequences and found that promoter sequences seem to have a tendency toward larger localization length, i.e., enhanced transport might point toward the importance of an electronic mechanism in the initial stages of DNA polymerase. However, these results warrant further investigation.