Influence of nanopore surface charge and magnesium ion on polyadenosine translocation.

We investigate the influence of a nanopore surface state and the addition of Mg(2+) on poly-adenosine translocation. To do so, two kinds of nanopores with a low aspect ratio (diameter ∼3-5 nm, length 30 nm) were tailored: the first one with a negative charge surface and the second one uncharged. It was shown that the velocity and the energy barrier strongly depend on the nanopore surface. Typically if the nanopore and polyA exhibit a similar charge, the macromolecule velocity increases and its global energy barrier of entrance in the nanopore decreases, as opposed to the non-charged nanopore. Moreover, the addition of a divalent chelating cation induces an increase of energy barrier of entrance, as expected. However, for a negative nanopore, this effect is counterbalanced by the inversion of the surface charge induced by the adsorption of divalent cations.