Voltammetric measurements of the interaction of metal complexes with nucleic acids

Abstract

Cyclic voltammetry and differential-pulse voltammetry at mm-sized electrodes were used to measure the decrease in the rate of diffusion of metal complexes upon binding to DNA and to extract the binding constants and effective binding site sizes. A linear correlation was observed between the site size determined electrochemically and the diameter of the complexes [site size: Cu(phen)2(2+) > Fe(phen)3(2+) > Co(bipy)3(3+) approximately Fe(bipy)3(2+) > Ru(NH3)6(3+)]. The binding constants were found to be influenced by the charge of the metal complex, the nature of ligand and the geometry about the metal centre. Competition experiments, in which differential pulse voltammetry was used to observe the release of bound metal complex on addition of a second DNA-binding molecule to the solution, were sensitive to the nature and location of the binding sites for the two species. Steady-state voltammetric experiments at microelectrodes are shown to have a number of advantages over cyclic voltammetry and differential pulse voltammetry at mm-sized electrodes for determination of binding constants. In particular, the steady-state diffusion limited current is directly proportional to the diffusion coefficient, rather than its square root, which improves the discrimination between DNA-bound and freely diffusing metal complex. Further, the kinetics of the binding process do not affect the steady state measurement, whereas for transient techniques, e.g., cyclic voltammetry, only a range of values can be extracted corresponding to the limits of fast and slow binding kinetics compared to the experimental timescale.

DNA Sensor for Recognition of Native Yeast DNA Sequence with Methylene Blue as an Electrochemical Hybridization Indicator

“…The similar difference of association constants in homogeneous solution and interfacial system has also been noted for the complex of Co(phen) 3 3 with dsDNA [22,44]. A value of the association constant was reported to be 1.74 Â 10 3 M À1 for the complex of Co(phen) 3 3 with immobilized dspoly(dG)poly(dc) [22], while 1.6 Â 10 4 M À1 for the complex of Co(phen) 3 3 with double-stranded calf thymus DNA in homogeneous solution was given [44]. Thus, the binding constant between DNA and indicator depends on both the variety of DNA and the experimental conditions such as ionic strength, concentration of indicator or DNA, pH value of solution and the microenvironment, even for a simple model intercalator, MB [36].…”

“…These values are less than the association constant of 6 Â 10 4 M À1 for the complex of MB with double-stranded calf thymus DNA in solution [33] and 3.8 Â 10 6 M À1 for the complex of MB with dsDNA mentioned in the literature [37]. The similar difference of association constants in homogeneous solution and interfacial system has also been noted for the complex of Co(phen) 3 3 with dsDNA [22,44]. A value of the association constant was reported to be 1.74 Â 10 3 M À1 for the complex of Co(phen) 3 3 with immobilized dspoly(dG)poly(dc) [22], while 1.6 Â 10 4 M À1 for the complex of Co(phen) 3 3 with double-stranded calf thymus DNA in homogeneous solution was given [44].…”

Voltammetric, UV–Vis Spectrometric and Fluorescence Study of the Interaction of Ractopamine and DNA with the Aid of Multivariate Curve Resolution‐Alternating Least Squares

“…A binding ratio is defined as the concentration ratio of the binding ligand to total ligand [6], and the binding number is regarded as the number of participating DNA sites [7]. The interaction of DNA with drugs has been studied by various techniques including fluorescence [8], UV-vis [9], FT-IR [10], luminescence [11], capillary electrophoresis [12], NMR [13], microgravimetry [14], electroanalytical methods [15] and surface plasmon resonance [16]. Voltammetry has also been used to study such interactions [17 -20], and the observed electrochemical signals can provide useful information about the interaction mechanism, binding constant and binding forces.…”

Electrochemical and Spectroscopic Studies of the Interaction of Proflavine with DNA

“…8,9 Several techniques have been employed to study the binding of small molecules to DNA including, for example, viscometry, 10 UV-Vis spectroscopy, 11 isothermal calorimetric titration, 12 luminescence, 13 electrophoresis, 14 fluorescence 15 and electroanalytical methods. [16][17][18][19][20][21] It has been shown that electrochemical techniques have several advantages in measuring the binding of small species to DNA, such as applicability over a wider range of binding constants than classical methods. 16,22 Several authors have shown that the binding constants for redox active species can be obtained from straightforward voltammetric experiments in which the DNA is titrated against the redox active molecule.…”