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Related Concept Videos

Potentiometry: Membrane Electrodes01:15

Potentiometry: Membrane Electrodes

Membrane electrodes, also known as p-ion electrodes, use membranes that selectively interact with free analyte ions, generating a potential difference across the membrane. The resulting membrane potential, known as the asymmetry potential, is not zero even when analyte concentrations on both sides of the membrane are equal. The membrane's response is typically not selective to a single analyte but proportional to the concentration of all ions in the sample solution capable of interacting at the...
Resting Membrane Potential01:24

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The relative difference in electrical charge, or voltage, between the inside and the outside of a cell membrane, is called the membrane potential. It is generated by differences in permeability of the membrane to various ions and the concentrations of these ions across the membrane.
The Inside of a Neuron is More Negative
The membrane potential of a cell can be measured by inserting a microelectrode into a cell and comparing the charge to a reference electrode in the extracellular fluid. The...
Resting Membrane Potential01:24

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The relative difference in electrical charge, or voltage, between the inside and the outside of a cell membrane, is called the membrane potential. It is generated by differences in permeability of the membrane to various ions and the concentrations of these ions across the membrane.
The Inside of a Neuron is More Negative
The membrane potential of a cell can be measured by inserting a microelectrode into a cell and comparing the charge to a reference electrode in the extracellular fluid. The...
The Resting Membrane Potential01:21

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Overview
Membrane Proteins01:30

Membrane Proteins

Plasma membranes have integral transmembrane proteins involved in facilitated transport. These proteins are collectively referred to as transport proteins, and they function as either channels for the material or as carriers themselves. Channel proteins have hydrophilic domains exposed to the intracellular and extracellular fluids and a hydrophilic channel through their core that provides a hydrated opening for solutes to pass through the membrane layers. Passage through the channel allows...
Membrane Proteins01:30

Membrane Proteins

Plasma membranes have integral transmembrane proteins involved in facilitated transport. These proteins are collectively referred to as transport proteins, and they function as either channels for the material or as carriers themselves. Channel proteins have hydrophilic domains exposed to the intracellular and extracellular fluids and a hydrophilic channel through their core that provides a hydrated opening for solutes to pass through the membrane layers. Passage through the channel allows...

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Membrane Potentials, Synaptic Responses, Neuronal Circuitry, Neuromodulation and Muscle Histology Using the Crayfish: Student Laboratory Exercises
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Published on: January 18, 2011

MEMBRANE POTENTIALS AND CATAPHORETIC POTENTIALS OF PROTEINS.

J Loeb1

  • 1Laboratories of The Rockefeller Institute for Medical Research.

The Journal of General Physiology
|October 30, 2009
PubMed
Summary
This summary is machine-generated.

Protein membrane potentials are governed by ion concentration differences, calculable via Donnan

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Reconstitution of a Kv Channel into Lipid Membranes for Structural and Functional Studies

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Last Updated: Jun 19, 2026

Membrane Potentials, Synaptic Responses, Neuronal Circuitry, Neuromodulation and Muscle Histology Using the Crayfish: Student Laboratory Exercises
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Reconstitution of a Kv Channel into Lipid Membranes for Structural and Functional Studies
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Published on: July 13, 2013

Area of Science:

  • Biophysics
  • Physical Chemistry

Background:

  • Membrane potentials in protein solutions/gels depend on ion concentration gradients, calculable using Donnan's equation.
  • Cataphoretic potentials of protein particles are theorized to arise from ion concentration differences within electrical double layers.

Purpose of the Study:

  • To investigate the relationship and discrepancies between membrane potentials and cataphoretic potentials in proteins.
  • To elucidate the forces governing cataphoretic migration and potential differences in protein particles.

Main Methods:

  • Analysis of membrane potentials based on Donnan's equation for membrane equilibria.
  • Application of Helmholtz's electrical double layer theory to understand cataphoretic potentials.
  • Experimental investigation of protein particle migration and potentials under varying conditions.

Main Results:

  • Both membrane and cataphoretic potentials show charge reversal relative to the isoelectric point.
  • Trivalent/tetravalent salts reverse cataphoretic potentials but only neutralize membrane potentials.
  • Protein-inherent forces, linked to membrane equilibrium, dominate over solution forces in determining cataphoretic migration.

Conclusions:

  • Membrane equilibrium significantly influences protein particle behavior and migration.
  • Discrepancies in salt effects highlight differences in the mechanisms of membrane and cataphoretic potentials.