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Gap Junctions

Gap Junctions

The cytoplasm of adjacent animal cells can exchange small molecules, ions, and secondary messengers via the communication channels which form the gap junctions. These junctions comprise a few hundred to thousands of molecular channels, each made of two halves, called the connexon hemichannel. A connexon is a hexamer of six transmembrane connexin proteins, which assemble radially, thus forming a pore or channel in the center. One connexon hemichannel docks with a corresponding connexon on the...

Gap Junctions

Gap Junctions

Multicellular organisms employ a variety of ways for cells to communicate with each other. Gap junctions are specialized proteins that form pores between neighboring cells in animals, connecting the cytoplasm between the two, and allowing for the exchange of molecules and ions. They are found in a wide range of invertebrate and vertebrate species, mediate numerous functions including cell differentiation and development, and are associated with numerous human diseases, including cardiac and...

Non-gated Ion Channels

Non-gated Ion Channels

Ion channels are specialized proteins on the plasma membrane that allow charged ions to pass down their electrochemical gradient. Their main function is to maintain the membrane potential which is critical for cell viability. These channels are either gated or non-gated and can transport more than a thousand ions within milliseconds for the cellular event to occur.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.

Non-gated Ion Channels

Non-gated Ion Channels

Ion channels are specialized proteins on the plasma membrane that allow charged ions to pass down their electrochemical gradient. Their main function is to maintain the membrane potential which is critical for cell viability. These channels are either gated or non-gated and can transport more than a thousand ions within milliseconds for the cellular event to occur.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.

Potentiometry: Membrane Electrodes

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...

Junction Potentials in Galvanic Cells

Junction Potentials in Galvanic Cells

The Nernst equation, derived under the assumption of thermodynamic equilibrium, calculates the electromotive force (emf) as the sum of potential differences at phase boundaries in a reversible cell without a liquid junction. However, in irreversible cells such as the Daniell cell, an additional potential difference named the liquid-junction potential (EJ) arises across the interface of two electrolyte solutions due to different ion diffusion rates. This EJ represents the potential difference...

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Related Experiment Video

Updated: Jun 6, 2026

Functional Assessment of Intestinal Tight Junction Barrier and Ion Permeability in Native Tissue by Ussing Chamber Technique

Functional Assessment of Intestinal Tight Junction Barrier and Ion Permeability in Native Tissue by Ussing Chamber Technique

Published on: May 26, 2021

Gap junction permeability: selectivity for anionic and cationic probes.

G Kanaporis¹, P R Brink, V Valiunas

¹Dept. of Physiology and Biophysics, State University of New York at Stony Brook, Stony Brook, NY 11794-8661, USA.

American Journal of Physiology. Cell Physiology

|December 15, 2010

Summary

This summary is machine-generated.

Connexin channels (Cx) show selective permeability to various solutes. This study found that connexin26, Cx40, Cx43, and Cx45 gap junction channels discriminate between solutes based on size and charge, impacting cell signaling.

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Last Updated: Jun 6, 2026

Functional Assessment of Intestinal Tight Junction Barrier and Ion Permeability in Native Tissue by Ussing Chamber Technique

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Published on: May 26, 2021

A Functional Assay for Gap Junctional Examination; Electroporation of Adherent Cells on Indium-Tin Oxide

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An Iodide-Yellow Fluorescent Protein-Gap Junction-Intercellular Communication Assay

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Area of Science:

Cell Biology
Biophysics
Molecular Biology

Background:

Gap junction channels, formed by connexins, facilitate direct cell-to-cell communication.
These channels allow passage of various molecules, influencing cellular functions.
Connexin subtypes exhibit distinct properties, including solute permeability.

Purpose of the Study:

To investigate the permeability of homotypic connexin26 (Cx26), Cx40, Cx43, and Cx45 gap junction channels to solutes of varying size and charge.
To determine how connexin type influences the selective passage of charged and uncharged molecules.

Main Methods:

Stable expression of Cx26, Cx40, Cx43, and Cx45 in HeLa cells.
Simultaneous measurement of junctional conductance and fluorescent probe cell-cell flux.
Assessment of permeability for cationic and anionic probes of different sizes.

Main Results:

All four connexins (Cx26, Cx40, Cx43, Cx45) allowed passage of both cationic and anionic probes, with connexin-dependent transfer rates.
Negatively charged probes showed permeability order: Cx43 > Cx45 > Cx26 > Cx40.
Positively charged probes exhibited different permeability orders, with some connexins showing weak charge selectivity and others demonstrating size-dependent discrimination.

Conclusions:

Connexin channels exhibit selectivity for solutes based on both size and charge.
This selectivity suggests that connexin-specific channel properties play a crucial role in regulating intercellular communication and cell signaling pathways.