Detection of single-base mismatch at distal end of DNA duplex by electrochemical impedance spectroscopy

Herein, we report an anomalous electrochemical behavior of surface-bound DNA duplex that has single-base mismatches at its distal end. Single-stranded 15-base DNA was immobilized at its 5'end onto gold electrode surfaces. After hybridization with complementary or mismatched DNA, electrochemical impedance spectra were obtained using [Fe(CN)(6)](3-/4-) as redox marker ions. Hybridization with the complementary DNA reduced the charge-transfer resistance (R-CT), whereas single-base mismatches at the distal end of the duplex largely increased the R-CT. This anomaly was found only with the distal end: the increase in R-CT was not observed for mismatches at either the middle or the proximal end. These results indicate that electrochemical detection of single-base alterations at an end of sample DNA is exceptionally easy because of the diametrically opposite responses. This detection principle is promising for the typing of single-nucleotide polymorphisms in combination with the single-base primer extension protocol. (c) 2006 Elsevier B.V. All rights reserved.