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Distribution of Metal Complexes Bound to DNA Determined by Normal Pulse Voltammetry

Welch, Thomas W. and Thorp, H. Holden (1996) Distribution of Metal Complexes Bound to DNA Determined by Normal Pulse Voltammetry. Journal of Physical Chemistry, 100 (32). pp. 13829-13836. ISSN 0022-3654. doi:10.1021/jp960251n.

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The effects of DNA binding on the normal pulse voltammetry of metal complexes have been investigated. Studies were performed both for oxidation of OsL_3^(2+/3+) and for reduction of CoL_3^(3+/2+) (L is bpy = 2,2‘-bipyridine or phen = 1,10-phenanthroline). The diffusive current obtained from voltammograms at potentials well past E_(1/2) gives an accurate measure of the extent to which the complexes codiffuse with DNA or are free in solution, and this response is not affected by kinetic factors resulting from slow heterogeneous electron transfer. Analysis of the diffusion-limited current using the appropriate binding isotherm provides binding constants in good agreement with those measured by other methods. For the bpy complexes, the ionic strength dependence, the relative binding constants for the 2+ and 3+ forms, and the associated change in E_(1/2) upon DNA binding are in good agreement with the predictions of polyelectrolyte theory where the 3+ ion binds more strongly. For the phen complexes, the reverse trend is observed and is consistent among the absolute binding constants, ionic strength dependence, and E_(1/2) shift; this behavior is ascribed to a hydrophobic interaction. The technique is also applied to two-electron couples based on [(tpy)(L)RuOH_2]^(2+)/[(tpy)(L)RuO]^(2+) that exhibit slow heterogeneous electron transfer; however, these kinetic complications do not prohibit accurate determination of the binding energetics using normal pulse voltammetry. Taken together, the data provide a comprehensive picture of the effects of partial DNA binding on voltammetry, which provides a basis for determining homogeneous kinetic rate constants for electrocatalytic DNA oxidation from voltammograms.

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Additional Information:© 1996 American Chemical Society. Received: January 25, 1996. This work was supported by the David and Lucile Packard Foundation. T.W.W. thanks the Department of Education for a graduate fellowship. H.H.T. is a Camille Dreyfus Teacher-Scholar.
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David and Lucile Packard FoundationUNSPECIFIED
Department of EducationUNSPECIFIED
Camille and Henry Dreyfus FoundationUNSPECIFIED
Issue or Number:32
Record Number:CaltechAUTHORS:20180720-144211418
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Official Citation:Distribution of Metal Complexes Bound to DNA Determined by Normal Pulse Voltammetry Thomas W. Welch and H. Holden Thorp The Journal of Physical Chemistry 1996 100 (32), 13829-13836 DOI: 10.1021/jp960251n
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88085
Deposited By: George Porter
Deposited On:23 Jul 2018 20:37
Last Modified:16 Nov 2021 00:23

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