Electrostatic energy barriers from dielectric membranes upon approach of translocating DNA molecules

Abstract

We probe the electrostatic cost associated with the approach phase of DNA translocation events. Within an analytical theory at the Debye-Hückel level, we calculate the electrostatic energy of a rigid DNA molecule interacting with a dielectric membrane. For carbon or silicon based low permittivity neutral membranes, the DNA molecule experiences a repulsive energy barrier between 10 k B T and 100 k B T. In the case of engineered membranes with high dielectric permittivities, the membrane surface attracts the DNA with an energy of the same magnitude. Both the repulsive and attractive interactions result from image-charge effects and their magnitude survive even for the thinnest graphene-based membranes of size d ≈ 6 Å. For weakly charged membranes, the electrostatic energy is always attractive at large separation distances but switches to repulsive close to the membrane surface. We also characterise the polymer length dependence of the interaction energy. For specific values of the membrane charge density, low permittivity membranes repel short polymers but attract long polymers. Our results can be used to control the strong electrostatic energy of DNA-membrane interactions prior to translocation events by chemical engineering of the relevant system parameters. C 2016 AIP Publishing LLC. [http://dx

Electrostatics of polymer translocation events in electrolyte solutions

“…The left panel illustrates the approach phase of the DNA that was scrutinized in Ref. 26. In the present work, we extend the model by including the most crucial phase of the DNA transport, namely, the actual translocation process depicted by the right panel of Fig.…”

“…4 in Ref. 26. Second, we emphasize that previous models that aimed at evaluating the electrostatic cost of DNA translocation events have focused exclusively on the energy of the translocating polymer inside the nanopore.…”

“…26 it was shown that in the case of a ds-DNA approaching a charged dielectric membrane, the electrostatic polymer grand potential associated with the presence of the membrane is composed of two contributions. These are the polymer-self energy ∆Ω pol induced by polymer-image charge interactions and the polymer-membrane charge interaction Ω pm ,…”

“…In Ref. 26, we showed that at the DH level, the electrostatic self-energy of the polymer interacting with the dielectric membrane reads…”

“…The theory is an extension of the model in Ref. 26, where we considered the approach of a DNA molecule towards planar membranes. In Section III, we scrutinize the effect of the membrane's dielectric permittivity, the electrolyte density, the polymer length, and the membrane charge on the translocation process.…”