Translocation of Star Polyelectrolytes through a Nanopore

Translocation Dynamics of an Active Filament through a Long-Length Scale Channel

Active filament translocation through a confined space is crucial for diverse biological processes. By using Langevin dynamics simulations, we investigate the translocation dynamics of an axially self-propelled chain through a channel. First, results show a suggestive reciprocal scaling of translocation time versus active force. Second, in the case of a long channel, we demonstrate a very intriguing nonmonotonic change of translocation time with increasing channel width. The driving force shows a similar trend, providing a consistent picture to understand the unexpected channel width effect. In particular, in a moderately broad channel, the disordered chain conformation results in a loss of driving force and thus inhibits translocation dynamics. Chain adsorption might occur in a wide channel, which accounts for a facilitated translocation. Lastly, we connect the translocation process to tension propagation (TP). A modified TP picture is proposed to interpret the waiting time distribution. Our work highlights the new phenomenology owing to the crucial interplay of activity and spacial confinement, which drives the translocation dynamics, going beyond the traditional entropic barrier scenario.

Dissipative particle dynamics simulations in colloid and Interface science: a review

Dissipative particle dynamics (DPD) is one of the most efficient mesoscale coarse-grained methodologies for modeling soft matter systems. Here, we comprehensively review the progress in theoretical formulations, parametrization strategies, and applications of DPD over the last two decades. DPD bridges the gap between the microscopic atomistic and macroscopic continuum length and time scales. Numerous efforts have been performed to improve the computational efficiency and to develop advanced versions and modifications of the original DPD framework. The progress in the parametrization techniques that can reproduce the engineering properties of experimental systems attracted a lot of interest from the industrial community longing to use DPD to characterize, help design and optimize the practical products. While there are still areas for improvements, DPD has been efficiently applied to numerous colloidal and interfacial phenomena involving phase separations, self-assembly, and transport in polymeric, surfactant, nanoparticle, and biomolecules systems.

Translocation of a looped polymer threading through a nanopore

Recent experiments reported that the complicated translocation dynamics of a looped DNA chain through a nanopore can be detected by ionic current blockade profiles. Inspired by the experimental results, we systematically study the translocation dynamics of a looped polymer, formed by three building blocks of a loop in the middle and two tails of the same length connected with the loop, by using Langevin dynamics simulations. Based on two entering modes (tail-leading and loop-leading) and three translocation orders (loop-tail-tail, tail-loop-tail, and tail-tail-loop), the translocation of the looped polymer is classified into six translocation pathways, corresponding to different current blockade profiles. The probabilities of the six translocation pathways are dependent on the loop length, polymer length, and pore radius. Moreover, the translocation times of the entire polymer and the loop are investigated. We find that the two translocation times show different dependencies on the translocation pathways and on the lengths of the loop and the entire polymer.

Polyelectrolyte Translocation through a Tortuous Nanopore

Although nanopores have shown tremendous promise for use in DNA sequencing, the rate of translocation through most pores studied previously is too rapid for the genetic information to be read accurately. In this study, dissipative particle dynamics simulations were employed to investigate the feasibility of using tortuous nanopores to control the rate of polyelectrolyte translocation. Unlike many previous studies, our simulation method incorporates the effects of hydrodynamic and electrostatic interactions and the spatial variation of electric field strength. The average translocation time, ⟨τ⟩, increases with the pore length and tortuosity but decreases as the pore width increases. For the longest pore investigated, the introduction of tortuosity results in ⟨τ⟩ increasing by as much as 187% as compared to a straight pore. The temporal variation of bond tension indicates that slower translocation in tortuous nanopores is caused by inhibition of tension propagation.

Flow-Induced Translocation of Star Polymers through a Nanopore

The flow-induced translocation of star polymers through a cylindrical nanopore has been studied using dissipative particle dynamics (DPD) simulations. The number of arms, f, was varied with the total number of monomers, N, kept constant. The effect of simulating the capture of the polymer into the pore upon the mean translocation time, <τ_t>, has been investigated by varying the chain's initial location. The results indicate that the incorporation of the capture process results in a reduction of <τ_t> by up to 15%. This is because the chain's initial location affects the extent of its stretching along the flow direction during translocation. <τ_t> exhibits nonmonotonic variation with f, in agreement with recently reported results for electric field-driven translocation of star polymers. Its value is larger and shows greater variation with f when the solvent quality is better. For the same value of f, the capture occurs faster in a good solvent. In addition, <τ_t> is greater for a semiflexible chain than its flexible counterpart as the time required for the branch point to enter the nanopore is longer in the former case.