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Register a new userInfluence of polymer-pore interactions on translocation
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We investigate the influence of polymer-pore interactions on the translocation dynamics using Langevin dynamics simulations. An attractive interaction can greatly improve translocation probability. At the same time, it also increases translocation time slowly for weak attraction while exponential dependence is observed for strong attraction. For fixed driving force and chain length the histogram of translocation time has a transition from Gaussian distribution to long-tailed distribution with increasing attraction. Under a weak driving force and a strong attractive force, both the translocation time and the residence time in the pore show a non-monotonic behavior as a function of the chain length. Our simulations results are in good agreement with recent experimental data.
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One of the most fundamental quantities associated with polymer translocation through a nanopore is the translocation time $tau$ and its dependence on the chain length $N$. Our simulation results based on both the bond fluctuation Monte Carlo and Molecular Dynamics methods confirm the original prediction $tausim N^{2 u+1}$, which scales in the same manner as the Rouse relaxation time of the chain except for a larger prefactor, and invalidates other scaling claims.
Using Langevin dynamics simulations, we investigate the influence of polymer-pore interactions on the dynamics of biopolymer translocation through nanopores. We find that an attractive interaction can significantly change the translocation dynamics. This can be understood by examining the three components of the total translocation time $tau approx tau_1+tau_2+tau_3$ corresponding to the initial filling of the pore, transfer of polymer from the textit{cis} side to the textit{trans} side, and emptying of the pore, respectively. We find that the dynamics for the last process of emptying of the pore changes from non-activated to activated in nature as the strength of the attractive interaction increases, and $tau_3$ becomes the dominant contribution to the total translocation time for strong attraction. This leads to a new dependence of $tau$ as a function of driving force and chain length. Our results are in good agreement with recent experimental findings, and provide a possible explanation for the different scaling behavior observed in solid state nanopores {it vs.} that for the natural $alpha$-hemolysin channel.
We study the driven translocation of polymers under time-dependent driving forces using $N$-particle Langevin dynamics simulations. We consider the force to be either sinusoidally oscillating in time or dichotomic noise with exponential correlation time, to mimic both plausible experimental setups and naturally occurring biological conditions. In addition, we consider both the case of purely repulsive polymer-pore interactions and the case with additional attractive polymer-pore interactions, typically occurring inside biological pores. We find that the nature of the interaction fundamentally affects the translocation dynamics. For the non-attractive pore, the translocation time crosses over to a fast translocation regime as the frequency of the driving force decreases. In the attractive pore case, because of a free energy well induced inside the pore, the translocation time can be a minimum at the optimal frequency of the force, the so-called resonant activation. In the latter case, we examine the effect of various physical parameters on the resonant activation, and explain our observations using simple theoretical arguments.
We investigate several scaling properties of a translocating homopolymer through a thin pore driven by an external field present inside the pore only using Langevin Dynamics (LD) simulation in three dimension (3D). Specifically motivated by several recent theoretical and numerical studies that are apparently at odds with each other, we determine the chain length dependence of the scaling exponents of the average translocation time, the average velocity of the center of mass, $<v_{CM}>$, the effective radius of gyration during the translocation process, and the scaling exponent of the translocation coordinate ($s$-coordinate) as a function of the translocation time. We further discuss the possibility that in the case of driven translocation the finite pore size and its geometry could be responsible that the veclocity scaling exponent is less than unity and discuss the dependence of the scaling exponents on the pore geometry for the range of $N$ studied here.
Using Langevin dynamics simulations, we investigate the dynamics of a flexible polymer translocation into a confined area under a driving force through a nanopore. We choose an ellipsoidal shape for the confinement and consider the dependence of the asymmetry of the ellipsoid measured by the aspect ratio on the translocation time. Compared with an isotropic confinement (sphere), an anisotropic confinement (ellipsoid) with the same volume slows down the translocation, and the translocation time increases with increasing the aspect ratio of the ellipsoid. We further find that it takes different time for polymer translocation into the same ellipsoid through major-axis and minor-axis directions, depending on the average density of the whole chain in the ellipsoid, $phi$. For $phi$ lower than a critical value $phi_c$, the translocation through minor axis is faster, and vice versa. These complicated behaviors are interpreted by the degree of the confinement and anisotropic confinement induced folding of the translocated chain.
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