Browsing by Subject "Dielectric membranes"

Now showing 1 - 3 of 3

Open Access
Dielectric trapping of biopolymers translocating through insulating membranes
(MDPI AG, 2018) Büyükdağlı, Şahin; Sarabadani, J.; Ala-Nissila, T.
Sensitive sequencing of biopolymers by nanopore-based translocation techniques requires an extension of the time spent by the molecule in the pore. We develop an electrostatic theory of polymer translocation to show that the translocation time can be extended via the dielectric trapping of the polymer. In dilute salt conditions, the dielectric contrast between the low permittivity membrane and large permittivity solvent gives rise to attractive interactions between the cis and trans portions of the polymer. This self-attraction acts as a dielectric trap that can enhance the translocation time by orders of magnitude. We also find that electrostatic interactions result in the piecewise scaling of the translocation time t with the polymer length L. In the short polymer regime L ≲ 10 nm where the external drift force dominates electrostatic polymer interactions, the translocation is characterized by the drift behavior τ ~ L2. In the intermediate length regime 10 nm. ≲ L ≲ kb -1 where kb is the Debye-Hückel screening parameter, the dielectric trap takes over the drift force. As a result, increasing polymer length leads to quasi-exponential growth of the translocation time. Finally, in the regime of long polymers L ≳ kb -1 where salt screening leads to the saturation of the dielectric trap, the translocation time grows linearly as τ ~ L. This strong departure from the drift behavior highlights the essential role played by electrostatic interactions in polymer translocation.
Open Access
Electrostatics of Polymer Translocation Events in Electrolyte Solutions
(American Institute of Physics Inc., 2016) Buyukdagli, S.; Ala-Nissila, T.
We develop an analytical theory that accounts for the image and surface charge interactions between a charged dielectric membrane and a DNA molecule translocating through the membrane. Translocation events through neutral carbon-based membranes are driven by a competition between the repulsive DNA-image-charge interactions and the attractive coupling between the DNA segments on the trans and the cis sides of the membrane. The latter effect is induced by the reduction of the coupling by the dielectric membrane. In strong salt solutions where the repulsive image-charge effects dominate the attractive trans-cis coupling, the DNA molecule encounters a translocation barrier of ∼10 kBT. In dilute electrolytes, the trans-cis coupling takes over image-charge forces and the membrane becomes a metastable attraction point that can trap translocating polymers over long time intervals. This mechanism can be used in translocation experiments in order to control DNA motion by tuning the salt concentration of the solution.
Open Access
Theoretical modeling of polymer translocation: from the electrohydrodynamics of short polymers to the fluctuating long polymers
(MDPI AG, 2019) Büyükdağlı, Şahin; Sarabadani, J.; Ala-Nissila, T.
The theoretical formulation of driven polymer translocation through nanopores is complicated by the combination of the pore electrohydrodynamics and the nonequilibrium polymer dynamics originating from the conformational polymer fluctuations. In this review, we discuss the modeling of polymer translocation in the distinct regimes of short and long polymers where these two effects decouple. For the case of short polymers where polymer fluctuations are negligible, we present a stiff polymer model including the details of the electrohydrodynamic forces on the translocating molecule. We first show that the electrohydrodynamic theory can accurately characterize the hydrostatic pressure dependence of the polymer translocation velocity and time in pressure-voltage-driven polymer trapping experiments. Then, we discuss the electrostatic correlation mechanisms responsible for the experimentally observed DNA mobility inversion by added multivalent cations in solid-state pores, and the rapid growth of polymer capture rates by added monovalent salt in α-Hemolysin pores. In the opposite regime of long polymers where polymer fluctuations prevail, we review the iso-flux tension propagation (IFTP) theory, which can characterize the translocation dynamics at the level of single segments. The IFTP theory is valid for a variety of polymer translocation and pulling scenarios. We discuss the predictions of the theory for fully flexible and rodlike pore-driven and end-pulled translocation scenarios, where exact analytic results can be derived for the scaling of the translocation time with chain length and driving force.