The chemical-physical basis for K+ permeation and selectivity in K+ channels has been the focus of attention of many theoretical and computational studies since the first crystal structure was obtained by the Mackinnon lab in 1998. Most of the previous studies reported focused on atomic descriptions of permeation events in the selectivity filter of K+ channels in their closed conformation. In t...

In narrow pore ion channels, ions and water molecules diffuse in a single-file manner and cannot pass each other. Under such constraints, ion and water fluxes are coupled, leading to experimentally observable phenomena such as the streaming potential. Analysis of this coupled flux would provide unprecedented insights into the mechanism of permeation. In this study, ion and water permeation thro...

A palladium composite membrane was prepared by electroless plating on oxidized porous stainless steel support (ox-PSS). Hydrogen permeation flux through this composite membrane was measured in the temperature range of 574-674K and the pressure difference of two sides of membrane up to 90kPa. A simplified resistance model was employed to analyze the permeation behavior of hydrogen through Pd/ox-...

The tight junction formation in Caco-2 cell monolayers was compared after 9 and 13 d of culture. Four different sized paracellular markers were simultaneously applied to the apical side of the monolayers. The transepithelial resistance and permeability coefficient of mannitol for the monolayers cultured for 13 d were 17.4 and 0.095 times those after 9 d, respectively. The tight junction structu...

We present a new Monte Carlo technique, kinetic Monte Carlo reaction path following (kMCRPF), for the computer simulation of permeation and large-scale gating transitions in protein channels. It combines ideas from Metropolis Monte Carlo (MMC) and kinetic Monte Carlo (kMC) algorithms, and is particularly suitable when a reaction coordinate is well defined. Evolution of transition proceeds on th...

The oxygen permeation flux through the perovskite membrane made of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) has been measured as a function of both the temperature and the oxygen pressure gradient across the membrane. A simple model for the surface exchange fluxes was used to understand the mechanism of the oxygen transport. The limiting step of the oxygen transport was found to be the bulk diffusion fo...

Ondansetron HCl delivery through oral route suffers due to its low bioavailability due to first-pass metabolism. Therefore, the microemulsion-based transdermal delivery may be a better substitute for it. The pseudoternary phase diagrams were constructed to determine compositions of microemulsions, and ondansetron HCl microemulsions for transdermal delivery were developed using isopropyl myrista...

In this work we present a comparison of different discretization techniques, in the context of finite volume formulation, for the solution of separation processes involving adsorption, absorption and permeation. The mathematical model developed assumes axially dispersed plug-flow, uniform bed/sorbent/membrane properties along the axial coordinate and negligible radial gradients. The algorithm u...

The difficulty in characterizing ion conduction through membrane channels at the level of individual permeation events has made it challenging to elucidate the mechanistic principles underpinning this fundamental physiological process. Using long, all-atom simulations enabled by special-purpose hardware, we studied K(+) permeation across the KV1.2/2.1 voltage-gated potassium channel. At experim...

The cytotoxic 48-mer peptide, polytheonamide B (pTB), from a marine sponge forms a β(6.3)-helix with an inner diameter of 4 Å and a length of 45 Å, features that allow the selective permeation of monovalent cations across targeted cell membranes. To characterize this long, narrow pore, electrophysiological examination using a planar lipid bilayer method was performed. The single-channel current...