Bioengineering Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8561, Japan.
Anal Sci. 2021 May 10;37(5):765-771. doi: 10.2116/analsci.20SCP21. Epub 2021 Jan 22.
Electrochemical impedance spectroscopy (EIS) was used to detect non-Watson-Crick base pairs of DNA. Thiol-modified DNA as a probe and mercaptohexanol (MCH) were co-immobilized to form a DNA/MCH mixed self-assembled monolayer on a gold electrode surface and then hybridized with complementary DNAs. The DNA layers were measured by the EIS method and interpreted by equivalent circuits. Every terminal base mismatch of the DNA duplex brought about an increase in the charge-transfer resistance (R), unlike the case with a fully matched DNA duplex. The value of R was highly sensitive to the number of base mismatches for both unpaired and overhang DNA at the terminal. For internal base mismatches, however, no significant increase in R was observed. These experimental results proved that the charge transfer of redox molecules to the electrode surface is largely hindered by an end fraying motion due to base unpairing and dangling overhang. EIS was able to detect these steric properties of DNA strands. Furthermore, an electrode modified with G-quadruplex (G4) DNA demonstrated the influences of bulkiness and loop structure on the accessibility of the redox probe to the electrode.
电化学阻抗谱（EIS）被用于检测 DNA 的非沃森-克里克碱基对。巯基修饰的 DNA 作为探针，与巯基己醇（MCH）共同固定在金电极表面，形成 DNA/MCH 混合自组装单层，然后与互补 DNA 杂交。通过 EIS 方法测量 DNA 层，并通过等效电路进行解释。与完全匹配的 DNA 双链体不同，DNA 双链体的每个末端碱基错配都会导致电荷转移电阻（R）增加。对于末端未配对和悬垂 DNA 的碱基错配数量，R 的值高度敏感。然而，对于内部碱基错配，没有观察到 R 的显著增加。这些实验结果证明，由于碱基错配和悬垂突出，电化学中氧化还原分子向电极表面的电荷转移在很大程度上受到末端磨损运动的阻碍。EIS 能够检测到这些 DNA 链的空间性质。此外，用 G-四链体（G4）DNA 修饰的电极证明了体积和环结构对氧化还原探针到达电极的可及性的影响。
