A Redox-Reversible Switch of DNA Hydrogen Bonding and Structure.

Modulating molecular structure and function at the nanoscale drives innovation across wide-ranging technologies. Electrical control of the bonding of individual DNA base pairs endows DNA with precise nanoscale structural reconfigurability, benefiting efforts in DNA origami and actuation. Here, alloxazine DNA base surrogates were synthesized and incorporated into DNA duplexes to function as a redox-active switch of hydrogen bonding. Circular dichroism (CD) revealed that 24-mer DNA duplexes containing one or two alloxazines exhibited CD spectra and melting transitions similar to DNA with only canonical bases, indicating that the constructs adopt a B-form conformation. However, duplexes were not formed when four or more alloxazines were incorporated into a 24-mer strand. Thiolated duplexes incorporating alloxazines were self-assembled onto multiplexed gold electrodes and probed electrochemically. Square-wave voltammetry (SWV) revealed a substantial reduction peak centered at -0.272 V vs Ag/AgCl reference. Alternating between alloxazine oxidizing and reducing conditions modulated the SWV peak in a manner consistent with the formation and loss of hydrogen bonding, which disrupts the base pair stacking and redox efficiency of the DNA construct. These alternating signals support the assertion that alloxazine can function as a redox-active switch of hydrogen bonding, useful in controlling DNA and bioinspired assemblies.