Publication
596
J.
Am. Chem. Soc. 128( 2 ), 542 - 557 , 2006 .
DOI: 10.1021/ja0561136
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Dynamics of Electron Transport by Elastic Bending of Short
DNA Duplexes. Experimental Study and Quantitative Modeling
of the Cyclic Voltammetric Behavior of 3'-Ferrocenyl DNA
End-Grafted on Gold
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Agnès Anne* and Christophe Demaille*
Contribution from the Laboratoire d'Electrochimie Moléculaire, Université de Paris 7-Denis Diderot, 2 place Jussieu,75251 Paris Cedex 05, France
The dynamics of electron transport within a molecular monolayer of 3'-ferrocenylated-(dT)20
strands, 5'-thiol end-grafted onto gold electrode surfaces via a short C2-alkyl linker, is analyzed using
cyclic voltammetry as the excitation/measurement technique. It is shown that the single-stranded DNA
layer behaves as a diffusionless system, due to the high flexibility of the ss-DNA chain. Upon hybridization
by the fully complementary (dA)20 target, the DNA-modified gold electrode displays a highly unusual
voltammetric behavior, the faradaic signal even ultimately switching off at a high enough potential scan
rate. This remarkable extinction phenomenon is qualitatively and quantitatively justified by the model of
elastic bending diffusion developed in the present work which describes the motion of the DNA-borne
ferrocene moiety as resulting from the elastic bending of the duplex DNA toward and away from the electrode
surface. Its use allows us to demonstrate that the dynamics of electron transport within the hybridized
DNA layer is solely controlled by the intrinsic bending elasticity of ds-DNA. Fast scan rate cyclic voltammetry
of end-grafted, redox-labeled DNA layers is shown to be an extremely efficient method to probe the bending
dynamics of short-DNA fragments in the submillisecond time range. The persistence length of the end-anchored ds-DNA, a parameter quantifying the flexibility of the nanometer-long duplex, can then be
straightforwardly and accurately determined from the voltammetry data. |
