Book of Abstracts - Ruhr-Universität Bochum

P-64
ISBOMC `10 5.7 – 9.7. 2010 Ruhr-Universität Bochum
Electrochemical Studies of Fc-PNA(•DNA) Surface Dynamics
Nina Hüsken, a Magdalena Gębala, b Wolfgang Schuhmann b and Nils Metzler-Nolte *a
a Ruhr-Universität Bochum, Fakultät für Chemie und Biochemie, Lehrstuhl für Bioanorganische
Chemie, Universitätsstrasse 150, 44801 Bochum, Germany. b Ruhr-Universität Bochum, Fakultät für
Chemie und Biochemie, Analytische Chemie, Universitätsstrasse 150, 44801 Bochum, Germany. Email:
nina.huesken@rub.de
The application of peptide nucleic acids (PNA) as receptor molecules in DNA biosensors promises an
enhanced specificity and selectivity for the analysis of DNA, due to the favourable hybridization
properties of PNA. N-terminal ferrocene (Fc) labelled and C-terminal gold surface confined PNA
oligomers present unique tools for electrochemical DNA biosensing, since structural and
conformational changes of the nucleic acid strand directly affect the Fc-electrode redox process. 1
By means of fast scan cyclic voltammetry (FSCV), the kinetic of the Fc-electrode redox process was
studied at Fc-PNA(•DNA) modified gold electrodes. The gold surfaces were loosely packed (< 8%)
with Fc-PNA(•DNA) single or double strands, to exclude any lateral interactions between the probe
molecules and to facilitate with this an unrestricted thermal strand motion of the Fc tethered strands.
These studies primary revealed, that the large elasticity of the PNA single strand evokes a diffusion
like motion of the Fc head group (“Fc-on-rope”), whereas the Fc label attached to the rather rigid
PNA(•DNA) duplex exhibits a significantly less diffusional behaviour (“Fc-on-rod”). Based on the
FSCV studies, a clear correlation between the determined electron transfer (ET) rate constants k 0 and
the inherent strand elasticity was developed. Thereby a large strand elasticity leads at high scan rates
to a ‘kinetic freeze’ of the tethered Fc head groups, to result in a large spectrum of Fc-electrode
distances and a large average Fc-electrode distance, being correlated to a rather low ET rate constant.
Vice versa, an increase in the strand rigidity leads to a smaller spectrum of possible Fc-electrode
distances and an average Fc-electrode distance, which is located closer to the gold surface due to an
attractive effect exerted by the electric field and hence correlates a larger ET rate constant. 2
Concluding, the established correlation between the Fc-electrode ET rate constants, determined by
FSCV, and the inherent PNA(•DNA) strand elasticity renders the ET rate constants a new means to
study Fc-PNA(•DNA) surface dynamics. This correlation furthermore presents the basis for an
electrokinetic analysis of DNA with Fc-PNA biosensors.
References
1. N. Hüsken, M. Gębala, W. Schuhmann, N. Metzler-Nolte, ChemBioChem 2010, DOI:
10.1002/cbic.200900748
2. N. Hüsken, M. Gębala, W. Schuhmann, N. Metzler-Nolte, manuscript submitted.
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