Influence of alternating current electrokinetic forces and torque on the elongation of immobilized DNA

Abstract

Articles you may be interested inThe authors investigate the elongation and orientation of different-sized deoxyribose nucleic acid (DNA) molecules, tethered onto gold electrodes via a terminal thiol, under the influence of high frequency ac electric fields. The DNA molecules are elongated from a random coil into an extended conformation and orientated along the electric field lines as a result of the forces acting on the molecules during the application of the ac electric fields. Elongation was observed in the frequency range 100 kHz-1 MHz, with field strengths of 0.06-1.0 MV/ m. Maximum elongation for all DNA fragments tested, irrespective of size, was found for frequencies between 200 and 300 kHz. The torque acting on the induced dipole in the DNA molecules, complemented by a directional bias force, opposite in direction to the dielectrophoretic force, provides the main contribution to the elongation process. The length of elongation is limited to either half the distance between opposing electrodes or to the contour length of the DNA, whichever is shorter. Further, the authors show that the normalized length of the elongated DNA molecules is independent of the contour length of the DNA.

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Molecular Self-Assembly: A Toolkit for Engineering at the Nanometer Scale

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“…The flow generates a drag force that can surpass DEP force and prevents the DNA from being trapped by the electrodes. [26] Several design features and experimental conditions have been optimized to reduce EHD effect to its undetectable level. The chamber height has been reduced to minimize vertical vortex formation by confinement.…”

“…No trapping is possible between facing electrodes without the floating electrode because the upstream flow generated at the median vertical plane in the electrode mid-gap prevents the bridge formation. [26] Rectangular electrodes with rounded corners (Figure 1 c) are chosen to avoid sharp angles where the electrical field would concentrate and generate "hot points". Finally, DI water is always used to minimize EHD, due to the low medium conductivity.…”