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Voltammetric measurements of the interaction of metal complexes with nucleic acids

Lookup NU author(s): Professor Andrew Houlton, Dr Ben Horrocks

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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+) approximate to 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.


Publication metadata

Author(s): Aslanoglu M, Isaac CJ, Houlton A, Horrocks BR

Publication type: Article

Publication status: Published

Journal: Analyst

Year: 2000

Volume: 125

Issue: 10

Pages: 1791-1798

ISSN (print): 0003-2654

ISSN (electronic): 1364-5528

Publisher: Royal Society of Chemistry

URL: http://dx.doi.org/10.1039/b005440m

DOI: 10.1039/b005440m


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