In this article, we simulate the translocation of a semiflexible homopolymer through an extended pore, driven by both a constant and a time-dependent end-pulled force, employing a model introduced in previous studies. The time dependence is simplistically modeled as a cosine function, and we distinguish between two scenarios for the driving--longitudinal force and transversal force-depending on the relative orientation of the force, parallel or perpendicular, respectively, with respect to the pore axis. Besides some key differences between the two drivings, the mean translocation times present a large minimum region as a function of the frequency of the force that is typical of the resonant activation effect. The presence of the minimum is independent on the elastic characteristics of the polymeric chains and reveals a linear relation between the optimum mean translocation time and the corresponding period of the driving. The mean translocation times show different scaling exponents with the polymer length for different flexibilities. Lastly, we derive an analytical expression of the mean translocation time for low driving frequency, which clearly agrees with the simulations.
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http://dx.doi.org/10.1103/PhysRevE.108.034501 | DOI Listing |
mSphere
January 2025
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Unlabelled: During infection, bacterial pathogens rely on secreted virulence factors to manipulate the host cell. However, in gram-positive bacteria, the molecular mechanisms underlying the folding and activity of these virulence factors after membrane translocation are not clear. Here, we solved the protein structures of two secreted parvulin and two secreted cyclophilin-like peptidyl-prolyl isomerase (PPIase) ATP-independent chaperones found in gram-positive streptococcal species.
View Article and Find Full Text PDFAnal Chem
January 2025
Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, United States.
The nuclear pore complex (NPC) is the proteinous nanopore that solely regulates molecular transport between the nucleus and cytoplasm of a eukaryotic cell. Hypothetically, the NPC utilizes the hydrophobic barriers based on the repeats of phenylalanine-glycine (FG) units to selectively and efficiently transport macromolecules. Herein, we quantitatively assess the hydrophobicity of transport barriers confined in the nanopore by applying scanning electrochemical microscopy (SECM).
View Article and Find Full Text PDFLangmuir
January 2025
Department of Electrical and Mechanical Engineering, Graduate School of Engineering, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan.
Second harmonic generation (SHG) measurements using SHG-active dye molecules have recently attracted attention as a method to detect the formation of pores in phospholipid bilayers. The bilayers, in which the dye molecules are embedded in the outer leaflet, exhibit a noncentrosymmetric structure, generating SHG signals. However, when pores form, these dye molecules translocate through the pores into the inner leaflet, leading to a more centrosymmetric structure and the subsequent loss of the SHG signals.
View Article and Find Full Text PDFShock
January 2025
Pharmacology, University of Vermont, Burlington, VT.
Objective: Loss of function of the phospholipid scramblase (PLS) TMEM16F results in Scott Syndrome, a hereditary bleeding disorder generally attributed to intrinsic platelet dysfunction. The role of TMEM16F in endothelial cells, however, is not well understood. We sought to test the hypothesis that endothelial TMEM16F contributes to hemostasis by measuring bleeding time and venous clotting in endothelial-specific knockout (ECKO) mice.
View Article and Find Full Text PDFBiochemistry
January 2025
BHF Centre of Research Excellence, School of Medicine and Life Sciences, King's College London, London SE1 9NH, United Kingdom.
Transmembrane glucose transport, facilitated by glucose transporters (GLUTs), is commonly understood through the simple mobile carrier model (SMCM), which suggests that the central binding site alternates exposure between the inside and outside of the cell, facilitating glucose exchange. An alternative "multisite model" posits that glucose transport is a stochastic diffusion process between ligand-operated gates within the transporter's central channel. This study aims to test these models by conducting atomistic molecular dynamics simulations of multiple glucose molecules docked along the central cleft of GLUT1 at temperatures both above and below the lipid bilayer melting point.
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