Base Pair Stacking Modulates Solid-State Charge Transport in DNA Hairpins

Particular interest has been focused on modulation of solid-state charge transport (CT) in DNA. Nevertheless, it remains challenging to do so in a sensitive and predictive manner due to the lack of a definite relationship between DNA base pair stacking and DNA CT. The challenges can be mainly attributed to the ill-defined systems, which may lead to ambiguous and even contradictory conclusions. Here, we use DNA hairpins to construct the well-defined self-assembled monolayers. We reveal nearly positive-linear correlations between DNA conformation and CT in the DNA hairpins regulated with metal ion chelation and DNA sequence. The correlations have been confirmed by the solid-state current-voltage characteristics and circular dichroism in solution. The enhanced CT via metal ion chelated DNA hairpins is mainly from the improved DNA energy coupling to electrodes, not the almost unchanged energy barrier when Hg ion-induced DNA conformational switches toward the canonical B-form.