Multiple DNA Binding Modes of a Metallointercalator Revealed by DNA Film Voltammetry

Abstract

Binding and the redox reaction of the metallointercalator Ru(bpy) 2 (dppz) 2+ (bpy ) 2,2′-bipyridine, dppz ) dipyrido[3,2-a:2′,3′-c]phenazine) with DNA was investigated by DNA film voltammetry. Calf-thymus DNA (CT-DNA) was assembled on a tin-doped indium oxide electrode by layer-by-layer electrostatic adsorption. Voltammetry of Ru(bpy) 2 (dppz) 2+ (Ru-dppz) bound to the DNA film was measured in a redox-free electrolyte and showed strong dependence on the concentration of the metallointercalator. At low Ru-dppz concentrations, a single oxidation peak was observed, the potential of which shifted from 1.25 to 1.1 V with increasing Ru-dppz concentration (peak 1). At high metal chelate concentrations, an additional oxidation peak emerged with a potential of 1.25 V which was unaffected by the Ru-dppz concentration (peak 2). Three experiments were performed to investigate the mechanism and structural basis of the multiple peaks. First, voltammetry of Os(bpy) 2 (dppz) 2+ bound to the CT-DNA film displayed only one peak at its oxidation potential of about 0.75 V. Second, the concentration dependence of Ru-dppz bound to a poly-(AU) film (which does not contain any guanine bases) exhibited only one oxidation peak at about 1.22 V that was independent of the Ru-dppz concentration. Third, when the guanine concentration in a mixed film of CT-DNA and poly-(AU) was changed and the bound Ru-dppz was kept constant, a pre-peak emerged and shifted to 1.1 V with increasing guanines. Based on these results, the appearance of two peaks in the voltammetric measurements of CT-DNA was rationalized by invoking two different DNA binding modes for the Ru-dppz complex: intercalation and electrostatic association. Peak 2 arises from slow oxidation of guanines catalyzed by Ru-dppz electrostatically associated with the DNA film, since the addition of Mg 2+ decreases the magnitude of peak 2. Peak 1 was not affected by Mg 2+ ions, leading us to conclude that it is due to intercalated Ru-dppz. The intercalation positions the metal complex in close contact with the guanines inside DNA resulting in fast electrocatalytic reaction, giving rise to a catalytic pre-peak.

Nucleic Acids Analytical Methods for Viral Infection Diagnosis: State-of-the-Art and Future Perspectives

“…Some of these are complex, composed of metals (such as osmium, ruthenium, etc.) that have been properly engineered to have the metallic center covalently bound to a planar intercalating ligand, such as phenanthroline, bypiridine derivates (BPY), or dipyridophenazine (DPPZ) [ 31 , 32 , 33 , 34 ]. As reported in Figure 3 , the redox activity of these probes allows electrochemical detection in the NAT method that brings the advantages of a high level of miniaturizability and good sensitivity and robustness, which are ideal for integration into PoC systems.…”

High catalytic activity of indium tin oxide nanoparticle modified electrode towards electro-oxidation of ascorbic acid

“…The slices were ultrasonically cleaned according to the published procedure [23], dried in an oven at 50°C, followed by treating for 60 s with an Atmospheric Plasma Surface Treatment Systems CTD-1000z from Kulun Electronics Co., Ltd. (Nanjing, Jiangsu, China). ITO nanoparticle solution (10 wt%, with a primary particle size of 20-30 nm) was purchased from Shanghai Huzheng Nanotechnology Co., Ltd. (Shanghai, China).…”

Electrochemical probe of natural DNA attached onto the gold–thiol SAMs via Zr(IV) ion glue

“…For the immobilization of unmodified natural DNA, more appropriate procedures should be investigated. Several schemes have been explored to this aim, among which, electrostatic adsorption of natural DNA on the electrode surface without any functionalization of DNA [17] seems to be an interesting and highly promising. This is the main purpose of the present work.…”