established between the SBP-heme centers and the electrode via the redox polymer. This contact enables the electrocatalytic reduction of H O to

Figure 9 shows that overloading of the redox polymer film with the probe oligonucleotide reduces the current after the SBP-labeled hybrid is formed. The current increases initially (Figure 9, curves a, b, and c) as the amount of probe is built up and more of the SBPlabeled target is captured. However, when the amount of probe is excessive, the current decreases and the rate of hybridization, evidenced by the rate of change in current, also slows (Figure 9, curve d). The apparent cause of the reduction in current is again the restriction of the movement