Potassium and thallium indicators, which exhibit an increase in fluorescence upon binding K⁺ or Tl⁺, can be used to measure the activity of potassium channels and transporters.

Potassium Channel Assays

Potassium (K⁺) in physiology

Because expanding our knowledge of K⁺ channels and K⁺ transporters is of such intense interest to both basic and drug discovery researchers, a facile means to measure their activity is critical. Unfortunately, measuring intracellular and extracellular K⁺ levels and dynamics using fluorescent indicators is challenging. In most cells at rest, cytoplasmic K⁺ concentrations are above 100 mM while Na⁺ concentrations are in the 3 – 5 mM range. Conversely, extracellular K⁺ concentrations are typically in the 3-5 mM range while Na⁺ concentrations are above 100 mM. Therefore, an effective K⁺sensor needs to be able to discriminate between K⁺, Na⁺ and other common physiological cations while possessing a K⁺ affinity appropriate to detect physiologically relevant changes in K⁺ concentrations. Find more information about our potassium selective indicators here.

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Thallium flux assays for potassium channels

Potassium channel assays using thallium flux

Additional reagents included in all kits for improving indicator loading and retention, and reducing extracellular fluorescence

Although the AM forms of ION’s fluorescent K⁺ and Tl⁺ indicators readily cross the plasma membrane, there are other factors that can affect how well the indicators load into cells. Because AM forms of the indicators are quite hydrophobic, it is common to use the non-ionic surfactant, Pluronic F-127, to improve their solubility in aqueous solution thus improving their loading into cells. Pluronic F-127 at the concentrations employed for loading indicators into cells is generally well tolerated. While Pluronic F-127 isn’t absolutely essential for loading most fluorescent K⁺ and Tl⁺ indicators into cells, it is highly recommended.

Another factor that can affect cell loading and intracellular localization is the presence of transport proteins capable of transporting many ion-sensitive, fluorescent indicators. In many cell types, the activity of these transporters can result in compartmentalization of the indicators into intracellular compartments as well as extrusion of the indicators outside of the cell. Both of these processes can dramatically reduce the signal-to-background levels and in some cell types (e.g. CHO cells), make adequate loading of K⁺-selective fluorescent indicators nearly impossible. Fortunately, inhibitors of these transport proteins can be an effective means of improving cytoplasmic localization and indicator retention. ION offers a convenient, 100X ION-Pro inhibitor solution that may be used in conjunction with any of our K⁺-sensitive fluorescent indicators.

TRS is a masking solution that is composed of a membrane impermeable fluorescence quencher that reduces extracellular fluorescence. Inclusion of this reagent ensures the fluorescence you are measuring is coming from within your cells. Use of this reagent is not recommended for cell suspensions.

Be Brilliant! Explore our line of Potassium Channel Assays and Indicators

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Image Products Excitation Emission Kd Price Quantity Action
Brilliant thallium gold product packaging. A thallium flux assay for potassium channels, sodium channels, and more
Brilliant Thallium Gold
A potassium channel assay, and so much more. Brilliant Thallium Gold includes Thallos Gold - ION’s gold fluorescent (Ex/Em = 528/552 nm) thallium (Tl+) indicator. Red-shifted excitation and emission enable multiplexing with GFP-expressing cells or other green fluorescent indicators. Useful for fluorescence-based potassium (K+) channel assays and for studying a wide variety of monovalent cation channels (sodium channels), transporters, and GPCRs.
$211.00$473.00
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Brilliant thallium gold snapshot assay kit packaging, an option for potassium channel assays, sodium channel assays, and more
Brilliant Thallium Gold Snapshot
Brilliant Thallium Gold Snapshot is a multi-instrument compatible assay solution for well plate-based, high-throughput measurements of thallium flux through potassium, sodium, and non-selective cation channels, as well as some Na+ or K+ transporters. Our patent-pending Snapshot technology generates a long-lasting signal so you can easily detect and quantify changes in ion channel or transporter activity on most fluorescence-capable instruments. The inclusion of Thallos Gold AM, our red-shifted thallium indicator, makes this kit the ideal option when using GFP-expressing cells to run potassium channel assays.
$211.00$473.00
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Potassium channel assay for flow cytometry packaging.
Flow Cytometric Potassium Channel Assay
ION Biosciences’ Flow Cytometric Potassium Channel Assay is the first assay solution for single-cell, high-throughput measurements of potassium channel activity. Powered by our patent-pending Snapshot assay technology, ion channel modulation generates a long-lasting signal so you can easily detect and quantify changes in ion channel or transporter activity using Flow Cytometry. This kit may also work for sodium channels, non-selective cation channels, and some Na+ or K+ transporters. 200 assays.
$473.00
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Brilliant thallium snapshot packaging with an image demonstrating microscope compatibility
Brilliant Thallium Snapshot
An endpoint-compatible potassium channel assay. ION's Brilliant Thallium Snapshot kit is a thallium flux assay adaptation designed to work with standard plate readers, microscopes, flow cytometers, and more, for measuring flux through potassium (K⁺), sodium (Na⁺), and non-selective cation channels, transporters, and their effectors, including GPCRs.
$211.00$473.00
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Thallium flux assay packaging, a potassium channel assay and more
Brilliant Thallium
A potassium channel assay, and so much more. ION’s high-throughput, no wash thallium (Tl⁺) flux assay is an optimal solution for measuring the activity of potassium (K⁺), sodium (Na⁺), and non-selective cation channels and their effectors including transporters and GPCRs.
$211.00$3,597.00
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