Metal-dependent electrochemical discrimination of DNA quadruplex sequences

Films of four different DNA quadruplex-forming (G4) sequences (c-KIT, c-MYC, HTelo, and BCL2) on gold surfaces were investigated by electrochemical impedance spectroscopy (EIS) to evaluate whether they evoke unique electrochemical responses that can be used for their identification. This could render EIS an alternative means for the determination of G4 sequences of unknown structure. Towards, this end, cation-dependent topology changes in the presence of either K⁺, K⁺ in combination with Li⁺, or Pb²⁺ in the presence of Li⁺ were first evaluated by circular dichroism (CD) spectroscopy, and electrochemical studies were performed subsequently. As a result, G4-sequence specific charge transfer resistance (R_CT) patterns were in fact observed for each G4 sequence, allowing their discrimination by EIS.