(a) Conductance histograms at different gate voltages (Vg), where the red lines are Two-Gaussian fits, from which the areas of the low (Sox) and high (Sred) conductance peaks are determined. (b) Percentage of Aq-DNA in the oxidized form versus gate voltage obtained from the reduction (magenta curve) and oxidation (blue curve) peaks in the cyclic voltammograms with a sweeping rate of 0.1 V·s−1, and the high and low conductance peaks in the conductance histograms (black points). Red dashed line is guide to eye. (c) Log(Sox/Sred) versus gate voltages (Vg) and fitting of the data with the Nernst equation (red line). Peak area error is determined by the fitting error of the Gaussian distribution. Gate voltage error is determined by the variations in the quasi-reference electrode (Supplementary Fig. 3a).