Ion permeability of artificial membranes evaluated by diffusion potential and electrical resistance measurements

Abstract

In the present article, a novel model of artificial membranes that provides efficient assistance in teaching the origins of diffusion potentials is proposed. These membranes are made of polycarbonate filters fixed to 12-mm plastic rings and then saturated with a mixture of creosol and n-decane. The electrical resistance and potential difference across these membranes can be easily measured using a low-cost volt-ohm meter and home-made Ag/AgCl electrodes. The advantage of the model is the lack of ionic selectivity of the membrane, which can be modified by the introduction of different ionophores to the organic liquid mixture. A membrane treated with the mixture containing valinomycin generates voltages from -53 to -25 mV in the presence of a 10-fold KCl gradient (in to out) and from -79 to -53 mV in the presence of a bi-ionic KCl/NaCl gradient (in to out). This latter bi-ionic gradient potential reverses to a value from +9 to +20 mV when monensin is present in the organic liquid mixture. Thus, the model can be build stepwise, i.e., all factors leading to the development of diffusion potentials can be introduced sequentially, helping students to understand the quantitative relationships of ionic gradients and differential membrane permeability in the generation of cell electrical signals.

An intuitive approach to understanding the resting membrane potential

“…Ϫ on opposite sides of a dialysis membrane and using a pH meter as the detector. A similar approach was taken by Shlyonsky (18) in which polycarbonate filters were used to establish bioelectric potentials that could be recorded using a pH meter.…”

Motivation and Technology Acceptance in a Neuroscience Student Lab—An Empirical Comparison Between Virtual Experiments With and Without Hands-on Elements

“…To address the problem that neurophysiological processes are often not visible and difficult to understand, there is a whole range of teaching approaches and methods. For example, structural models for a better illustration of the neurobiological structures (Krontiris-Litowitz, 2003;Keen-Rhinehart et al, 2009) or functional models in which bioelectric potentials can be traced with simplified replicas of neurons (Dabrowski et al, 2013;Shlyonsky, 2013) can be used. However, visualization of nonvisible processes through analogies (Procopio, 1994;Milanick, 2009;Griff, 2018), explanatory models (Wright, 2004;Cardozo, 2016), or even role-playing (Carvalho, 2011;Holloway, 2013) are also part of the repertoire of neurobiological teaching approaches.…”

Mathematical expression of membrane potential based on Ling’s adsorption theory is approximately the same as the Goldman–Hodgkin–Katz equation

“…Since Selemion AMV is an anion exchange membrane, it does not appear to be inappropriate to postulate that its permeability to cation is quite low and that to anion is quite high. In the GHK equation, this postulation can be interpreted as the permeability constants are given by P K = 0 and P Cl = 1, respectively, and it leads to the GHK equation given by ( 2) [3,[10][11][12]. The computed potential obtained by using ( 2) is represented by the in Fig.…”

“…( 12) is derived using ( 8)- (11). Then, ( 15) is derived by solving (12) under the conditions of ( 13) and ( 14).…”