P3.8 - Novel electrochemical probes used to monitor structure-specific behaviour of oligonucleotides on charged electrode surface

15. Dresdner Sensor-Symposium 2021
2021-12-06 - 2021-12-08
P3. (Bio-)Medizinische Sensorik
A. Daňhel, M. Fojta - Institute of Biophysics of the CAS, Brno/CZ, D. Dobrovodský - Masaryk University, Brno/CZ
159 - 163


In the field of DNA structure study, a lot of interest is focused on the alternative DNA conformations known as G-quadruplexes (G4). These four-stranded structural motifs are present in cells as critical regulatory elements and are also of interest as potential targets in cancer therapy or nanotechnology building blocks. G4 are formed in nucleic acid sequences containing tracts of guanines that self-associate into square planar G-quartets stabilised by Hoogsteen hydrogen bonds. Individual G-quartets interact with each other via π-π stacking, and the final G4 structure is further stabilised by the presence of cations in its central cavity. The development of analytical tools for the recognition and study of G4 is of increasing relevance due to the growing interest in non-canonical DNA structures. Electroanalytical methods have been long established as practical tools for studying conformational changes of DNA molecules utilising intrinsic redox, as well as non-faradaic signals of DNA mainly obtained by voltammetry on mercury-based electrodes. For example, the structural transition between doubleand single-stranded DNA can be monitored by differential pulse or square wave voltammetry through a considerable increase of a cathodic peak corresponding to the reduction of nucleobases cytosine and adenine upon denaturation. This increase was attributed to better accessibility of reduction sites of these bases adsorbed at the electrode surface for the reduction in the denatured, single-stranded state. However, direct electrochemical analysis of short G4-forming oligodeoxynucleotides (ODNs) using a similar approach has proven difficult due to complex electrode processes related to guanine reduction. In this contribution, an alternative methodological approach for the distinction of G4 structure is proposed, based on voltammetric signals of novel electrochemical probes, the cationic metalloporphyrin meso-5,10,15,20-tetrakis(4-(N-methyl-pyridinium-4- yl)phenyl)porphyrinato copper(II) (Cu-TMPy2PP, Fig. 1a) and 7-(3-nitrophenyl)-7-deazaguanosine triphosphate (dGNPTP, Fig. 1b). on hanging mercury drop electrode (HMDE). Signals of these probes were used to monitor changes of accessible HMDE surface upon adsorption and/or selective desorption of various ODNs. It was shown that ODNs with the propensity to form G4 assemble into less dense layers at the electrode surface and are more prone to desorption by negative applied potential compared to single- and double-stranded ODNs, which can be used for their recognition.