Sequence-Specific Electron Transfer Mediated by DNA Duplexes Attached to Gold through the Alkanethiol Linker

Area of Science:

• Molecular Biophysics
• Electrochemistry
• Biotechnology

Background:

• The DNA double helix's electron transport capability is fundamental to biological and biotechnological processes.
• Understanding DNA's electronic properties is crucial for developing novel biosensors and understanding biological electron transfer mechanisms.

Purpose of the Study:

• To investigate the influence of DNA base composition on the efficiency of electron transfer (ET) mediated by the DNA π-stack.
• To compare ET rates in DNA duplexes rich in either (dAdT) or (dGdC) sequences versus mixed-composition DNA.

Main Methods:

• Utilized electrochemical methods to measure electron transfer rates from a gold electrode to DNA-bound methylene blue (MB).
• Investigated DNA-mediated ET in specific DNA sequences: (dAdT)25 and (dGdC)20, as well as mixed-composition DNA.
• Extrapolated ET rate constants to zero DNA surface coverage (ΓDNA → 0) for accurate comparison.

Main Results:

• Electron transfer rate constants were significantly higher in (dAdT)25 (121 ± 8 s⁻¹) compared to (dGdC)20 (67 ± 3 s⁻¹).
• DNA-mediated ET efficiency was lower in both homopolymer sequences ((dAdT) and (dGdC)) than in mixed-composition DNA.
• Observed differences are consistent with previously reported electric-field-induced structural variations in (dGdC) duplexes.

Conclusions:

• DNA base composition critically affects electron transfer efficiency, with (dAdT) sequences facilitating more efficient ET than (dGdC) sequences.
• The study provides new insights into biological electron transfer processes occurring in double-stranded DNA (dsDNA) with varying compositions at polarized interfaces.