Figure 7 The electrochemical response of DM noncovalently bound to a DNA film decreases when the immobilized duplexes contain a CA mismatch. (Adapted from Ref. 25.)

The range of mismatches that would result from genetic mutations requires an assay that is sensitive to mispairs of varying compositions. The electrochemical response of DM noncovalently bound to DNA-modified electrodes reported the presence of almost all types of mismatches [25]. In general, purine-pyrimidine and pyrimidine-pyrimidine mispairs (CA, TT, CC, GT, CT) caused the most pronounced attenuations in the current generated by the reduction of DM. The one purine-purine mispair studied, GA, could not be detected. Photophysical measurements of the effects of GA mispairs on long-range electron transfer through DNA also revealed an insensitivity to this sequence perturbation, likely due to the preservation of stacking interactions by this pair with increased aromatic surface area.