G-quadruplexes (G4) are stable alternative secondary structures of nucleic acids. With increasing understanding of their roles in biological processes and their application in bio- and nanotechnology, the exploration of novel methods for the analysis of these structures is becoming important. In this work, N-methyl mesoporphyrin IX (NMM) was used as a voltammetric probe for an easy electrochemical detection of G4s. Cyclic voltammetry on a hanging mercury drop electrode (HMDE) was used to detect NMM with a limit of detection (LOD) of 40 nM. Characteristic reduction signal of NMM was found to be substantially higher in the presence of G4 oligodeoxynucleotides (ODNs) than in the presence of single- or double-stranded ODNs and even ODNs susceptible to form G4s but in their unfolded, single-stranded forms. Gradual transition from unstructured single strand to G4, induced by increasing concentrations of the G4 stabilizing K⁺ ions, was detected by an electrochemical method for the first time. All obtained results were supported by circular dichroism spectroscopy. This work expands on the concept of electrochemical probes utilization in DNA secondary structure recognition and offers a proof of principle that can be potentially employed in the development of novel electroanalytical methods for nucleic acid structure studies.

G-四链体 (G4) 是稳定的核酸替代二级结构。随着人们对它们在生物过程中的作用及其在生物和纳米技术中的应用的日益了解，探索分析这些结构的新方法变得越来越重要。在这项工作中，N-甲基中卟啉 IX (NMM) 被用作伏安探针，可轻松电化学检测 G4s。使用悬汞滴电极 (HMDE) 上的循环伏安法检测 NMM，检测限 ( LOD)为 40 nM。发现在存在 G4 寡脱氧核苷酸 (ODN) 的情况下，NMM 的特征性还原信号明显高于存在单链或双链 ODN 的情况，甚至高于存在易形成 G4 但处于未折叠单链形式的 ODN 的情况。首次通过电化学方法检测到由G4 稳定 K ⁺离子浓度增加诱导的从非结构化单链到 G4 的逐渐转变。所有获得的结果均得到圆二色光谱的支持。这项工作扩展了 DNA 二级结构识别中电化学探针应用的概念，并提供了可用于开发核酸结构研究的新型电分析方法的原理证明。