Delocalization-Assisted Transport through Nucleic Acids in Molecular Junctions

Area of Science:

• Molecular electronics
• Biophysics
• Supramolecular chemistry

Background:

• Charge transport through molecules is crucial for supramolecular machines and nucleic acid functions like signaling and repair.
• Understanding electron transport mechanisms in nucleic acids is key to their biological roles.

Purpose of the Study:

• To investigate electron transport mechanisms in peptide nucleic acids (PNAs) with a G-block structure.
• To compare charge transport properties of PNAs with those of DNA duplexes.
• To analyze the factors influencing conductance oscillations in G-block nucleic acid duplexes.

Main Methods:

• Scanning tunneling microscopy (STM) break junction measurements were performed on G-block PNA duplexes.
• Conductance measurements were contrasted with previous findings for DNA duplexes of identical sequences.
• Theoretical analysis was employed to understand electronic coupling and electrode interactions.

Main Results:

• G-block PNA duplexes exhibited significantly higher conductance than corresponding DNA duplexes.
• Unlike DNA, G-block PNA duplexes did not show strong even-odd dependence conductance oscillations.
• Theoretical analysis indicated suppressed oscillation magnitude in PNA due to enhanced electronic coupling and PNA-electrode interactions.
• G-block PNA duplexes achieved molecular conductances up to 3% of the quantum of conductance (G0) for 5 nm lengths.

Conclusions:

• PNAs offer superior electron transport capabilities compared to DNA, with potential applications in molecular electronics.
• The suppression of conductance oscillations in PNAs is attributed to stronger electronic interactions within the molecule and with electrodes.
• This study provides insights into the fundamental mechanisms governing charge transport in synthetic and natural nucleic acid structures.