Biomaterial Database

Unstirred layer effects on calculations of the potential difference across an ion exchange membrane. 1977

R J French

The potential difference between two solutions of the same 1:1 electrolyte bathing an ion exchange membrane has been calculated as the sum of the following components: (a) a Donnan potential at each membrane-solution interface, (b) a diffusion potential within the membrane phase, and (c) a diffusion potential in the unstirred layer on each side of the membrane. For a highly charged ion exchange membrane with at least one surface in contact with a dilute solution, calculated transmembrane potential differences are extremely sensitive to the assumed thickness of the unstirred layers. This sensitivity to unstirred layer thickness is primarily due to changes in the Donnan components of the potential difference. By this approach, it was possible to fit membrane potential data from Gunn and Curran (1971, Biophys. J. 11:559) for a range of bathing solution concentrations from 0.0016 to 4.0 M. If no effort was made to account for the modification of the Donnan potentials by the presence of unstirred layers, the data appeared incompatible with an electrodiffusion equation description. Suggestions for a more stringent experimental test and a brief discussion of possible implications for electrical measurements on fresh-water giant algal cells are presented.

UI	MeSH Term	Description	Entries
D007474	Ion Exchange	Reversible chemical reaction between a solid, often one of the ION EXCHANGE RESINS, and a fluid whereby ions may be exchanged from one substance to another. This technique is used in water purification, in research, and in industry.	Exchange, Ion
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D010539	Permeability	Property of membranes and other structures to permit passage of light, heat, gases, liquids, metabolites, and mineral ions.	Permeabilities
D004058	Diffusion	The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space. Diffusion, especially FACILITATED DIFFUSION, is a major mechanism of BIOLOGICAL TRANSPORT.	Diffusions