Thermal Tunneling of Homopolymers through Amphiphilic Membranes

Abstract

We propose a theory to predict the passive translocation of flexible polymers through amphiphilic membranes. By using a generic model for the potential felt by a monomer across the membrane we calculate the free energy profile for homopolymers as a function of their hydrophobicity. Our model explains the translocation window and the translocation rates as a function of chain hydrophobicity in quantitative agreement with simulation results. The potential model leads to a new adsorption transition where chains switch from a one-sided bound adsorbed state into a bridging state through the membrane core by increasing the hydrophobicity beyond a critical value. We demonstrate that the hydrophobicity leading to the fastest translocation coincides with the solution for the critical point of adsorption in the limit of long chains.

Neural network learns physical rules for copolymer translocation through amphiphilic barriers

“…We calculated the mean first escape time τ as a measure for polymer translocation time through the model membrane all 2 N binary sequences up to chain length N ≤ 16. Our results confirm that polymer translocation is controlled by a balance of the overall hydrophobicity of the polymer, and is inhibited by adsorption at the bilayer-solvent interfaces s [28][29][30]32], which is consistent with the picture for small solutes [50] and larger solid objects such as carbon-nano-tubes [51].…”

“…Here, polymer translocation can be considered as the diffusion of its center of mass along an effective free energy landscape determined by the self-assembled membrane environment [26][27][28]. Translocation of homopolymers through bilayer membranes was recently understood theoretically by means of propagators as the solution of Edwards equation [29] in good agreement with coarse grained simulations [30]. Any inhomogeneity in polymer sequence renders the problem more complex being then equivalent to solving Schroedinger's equation in time-dependent potentials.…”

Shape-Adaptive Single-Chain Nanoparticles Interacting with Lipid Membranes

“…Therefore, objects with sizes greater than d , uptaken by the bilayer, would experience a squeezing force pushing them toward a flat shape. One example is the interplay between shape and hydrophobic interactions of linear polymers inserted into lipid bilayers. − It was shown that the uptake of homopolymers into a lipid bilayer is associated with an adsorption–desorption transition, controlled by hydrophobicity of the homopolymer. At a critical point, corresponding to a balanced hydrophobicity, flexible homopolymers can freely translocate through lipid bilayers.…”

Decoding Interaction Patterns from the Chemical Sequence of Polymers Using Neural Networks

“…The dependency of a 2 on alternating motifs of various block sizes is analyzed further in SI, section C. There, it is confirmed that a 2 increases with block size (Figure S7). Furthermore, the function F 2 (z) learned by the lin 2 transencoder is compared to an ideal chain model 43 considered in a double-well 25,31 potential (eq S13, Figure S8). In Figure S9, a good agreement is seen between F 2 and the solution for the ideal chain, including the training result for the longer chain, N = 20.…”

“…It is subject to a complex interplay between the conformation entropy and the local interactions of the monomers (eq S1). One expects that net hydrophilic polymers are repelled by the membrane’s core, while a hydrophobic polymer enters the lipid tail region. − The effective hydrophobic barrier of the membrane shall be expressible by a component F core in the landscape F ( z ). Another important contribution, F int , is the attraction of amphiphilic motifs toward the selective interface between T and H/S regions.…”