Ion Selectivity
Ion Selectivity - Related Videos
09:18
Measurement of Extracellular Ion Fluxes Using the Ion-selective Self-referencing Microelectrode Technique
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Cited by 6 •
2015
Transporters in cell membranes allow differential segregation of ions across cell membranes or cell layers and play crucial roles during tissue physiology, repair and pathology. We describe the ion-selective self-referencing microelectrode that allows the measurement of specific ion fluxes at single cells and tissues in vivo.
03:01
Characterizing Extracellular Space in a Brain Slice Using Ion-Selective and Iontophoresis Microelectrodes
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2025
This video demonstrates how to characterize the extracellular space in a brain slice by using ion-selective and iontophoresis microelectrodes to measure and compare electrical signals. This process helps determine the space's volume fraction and degree of twisting.
03:28
Selective Purification of a Bacterial Protein by Negative Ion-Exchange Chromatography
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2025
Source: Kuo, T., et al. One-step Negative Chromatographic Purification of Helicobacter pylori Neutrophil-activating Protein Overexpressed in Escherichia coli in Batch Mode. J. Vis. Exp. (2016)The video demonstrates a negative chromatography technique to purify a virulence-associated protein from a bacterial lysate. By using a positively charged resin in a buffered solution, host-cell proteins are selectively retained, while the near-neutral target protein remains unbound and is collected in the...
08:39
Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins
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Cited by 26 •
2017
This article describes how the ion selectivity of channelrhodopsin is determined with electrophysiological whole-cell patch-clamp recordings using HEK293 cells. Here, the experimental procedure for investigating chloride selectivity of an anion-selective channelrhodopsin is demonstrated. However, the procedure is transferable to other channelrhodopsins of distinct selectivity.
10:22
In Situ SIMS and IR Spectroscopy of Well-defined Surfaces Prepared by Soft Landing of Mass-selected Ions
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Cited by 4 •
2014
Soft landing of mass-selected ions onto surfaces is a powerful approach for the highly-controlled preparation of novel materials. Coupled with analysis by in situ secondary ion mass spectrometry (SIMS) and infrared reflection absorption spectroscopy (IRRAS), soft landing provides unprecedented insights into the interactions of well-defined species with surfaces.
FAQs
The molecular filter favors ions whose charge and dimensions fit its structure while helping stabilize them during passage. Charged amino acids within the pore contribute to this matching process, and the ion’s hydration state also affects compatibility. Small changes in filter geometry or charge can therefore alter which ions cross and how selectively the channel functions.
Selectivity determines which ions are permitted to use a pathway, whereas the electrochemical gradient provides the driving force for movement. An ion may fit the filter yet move only when the combined effects of concentration and electrical charge favor passage. This interaction allows selective pathways to influence membrane potential and cellular ion distribution.
Ion size affects whether a species can fit the pore, while hydration state describes its association with surrounding water molecules. The filter must accommodate the ion in a way that supports passage and stabilizes its charge. Consequently, two ions with related properties may experience different permeability through the same selective pathway.
These influences can modify the channel or its molecular filter, changing which ions are stabilized and allowed to pass. A mutation may alter pore geometry or charged amino acids, while a toxin or drug may interfere with channel function. The resulting shift in selectivity can change membrane behavior and contribute to physiological or disease-related effects.
Examining which ions cross a membrane pathway helps connect molecular filtering with larger cellular outcomes. Selective movement contributes to membrane potential, osmotic balance, nerve signaling, muscle contraction, and epithelial transport. Comparing normal and altered selectivity can therefore show how a membrane system regulates its internal environment and how disrupted transport affects biological function.
Selective ion movement helps establish and modify the electrical conditions of the membrane. In nerve cells, those changes support signaling, while in muscle cells they contribute to contraction. The same underlying control of ion passage links molecular channel properties to tissue-level activity, making selectivity relevant when channel function is changed by mutations, toxins, or drugs.