Electrical manipulation of oligonucleotides grafted to charged surfaces

Abstract

The electrical manipulation of short DNA molecules on surfaces offers novel functionalities with fascinating possibilities in the field of bio-interfaces. Here we present systematic investigations of the electrical interactions which govern the structure of oligonucleotides on charged gold surfaces. Successively, we address influences of the applied field strength, the role of DC electrode potentials, in particular for polycrystalline surfaces, as well as screening effects of the surrounding electrolyte solution. Data obtained for single and double stranded DNA exhibit differences which can be attributed to the dissimilar flexibility of the different molecular conformations. A comparison of the experimental results with a basic model shows how the alignment of the molecules adjusts according to a balance between electrically induced ordering and stochastic thermal motions. The presented conclusions are expected to be of general relevance for the behaviour of polyelectrolytes exposed to localized electric fields at interfaces.

Precisely Controlled Smart Polymer Scaffold for Nanoscale Manipulation of Biomolecules

“…The dependency on the buffer ionic strength holds for buffers of salts with different valencies. 25 The measured orientation for the negatively charged polymer (pH 7.6) matches well with the calculated results at low ionic strength, as the maximum orientation exceeds 70°( Figure 7B). At high ionic strength, the effects of negative charge on the polymer become negligible and the mean dsDNA orientation approaches 45°.…”

“…A first order model, presented previously by Rant, 25 is used to calculate the dependence of probe orientation as a function of the ionic strength. In the model, dsDNA probes are treated as freely rotating rigid rods anchored on a charged surface.…”

Real-time kinetics measurements of protein induced conformational changes in DNA

“…For low potentials the voltage potential, as a function of distance from the electrode, reduces to the Debye-Hückel equation, ψ ~ ψ 0 e -x/l d, where the Debye length appears as the characteristic decay length of the potential [5]. A large electric field results a few Debye lengths from the gold surface and exerts an electrostatic force on immobilized dsDNA that overcomes the Brownian motion, resulting in uniform alignment of the dsDNA in the electric field [6]. Due to the rapid decay of the electric field, the electrostatic force on the dsDNA and other charged molecules (such as charged proteins) becomes negligible at a few Debye lengths from the gold surface [6].…”

“…A large electric field results a few Debye lengths from the gold surface and exerts an electrostatic force on immobilized dsDNA that overcomes the Brownian motion, resulting in uniform alignment of the dsDNA in the electric field [6]. Due to the rapid decay of the electric field, the electrostatic force on the dsDNA and other charged molecules (such as charged proteins) becomes negligible at a few Debye lengths from the gold surface [6]. In a 60 mM monovalent salt solution the Debye length is ~1.2 nm.…”

The role of polarization-induced reorientation of DNA strands on organic field-effect transistor-based biosensors sensitivity at high ionic strength

“…As it will be shown in the following, the recorded sensitivity seems to be motivated by the effect of device polarization on the orientation of DNA single strands immobilized on the sensing surface of the device. Such a phenomenon was thoroughly investigated by Rant and co-workers 22,23 through the direct application of a voltage drop between a functionalized electrode and the solution. By switching the voltage, a persistent tilting of the oligonucleotides was obtained; in addition, the distribution of ions inside the solution, and so the screening length, was affected by a repulsion/attraction mechanism according to the sign of the voltage and the charge of the ions.…”