Intermediate tunnelling-hopping regime in DNA charge transport

Area of Science:

• Molecular electronics
• Biophysics
• Materials science

Background:

• Charge transport in molecular systems, including DNA, is fundamental to biological processes and electronic device applications.
• Existing models describe charge transport as either short-distance coherent tunneling or long-distance incoherent hopping.
• Understanding the nuances of charge transport in DNA is crucial for advancing molecular electronics.

Purpose of the Study:

• To investigate the charge transport mechanisms in single DNA molecules.
• To identify if intermediate charge transport regimes exist beyond coherent tunneling and incoherent hopping.
• To explore the influence of DNA sequence and length on charge transport properties.

Main Methods:

• Experimental measurement of charge transport across single DNA molecules bridged between two electrodes.
• Systematic variation of DNA sequence and length to observe effects on electrical resistance.
• Theoretical simulations to analyze molecular orbital delocalization and modeling based on Büttiker theory.

Main Results:

• DNA resistance generally increases linearly with length, consistent with incoherent hopping.
• Sequences with stacked guanine-cytosine (GC) base pairs exhibit periodic oscillations superimposed on the linear length dependence.
• Theoretical simulations confirm strong delocalization of highest occupied molecular orbitals in GC-rich DNA.

Conclusions:

• Evidence suggests an intermediate charge transport regime in double-stranded DNA where coherent and incoherent processes coexist.
• Guanine-cytosine rich sequences facilitate partial coherent transport, deviating from purely incoherent hopping.
• The findings provide a more comprehensive understanding of charge transport in DNA for potential electronic applications.