$173.00
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.
(EX 525 nm, EM 545 nm, Kd 50 mM) is the lowest affinity of the ION Potassium Green indicators. It is the indicator that is best positioned to respond to modest changes in intracellular K⁺ concentrations resulting from activation of plasma membrane K⁺ channels.
(EX 525 nm, EM 545 nm, Kd 18 mM) is the ION Potassium Green indicator with intermediate affinity. Currently, IPG-2 is our most popular intracellular K⁺ indicator.
(EX 525 nm, EM 545 nm, Kd 7 mM) has the highest K⁺ affinity of our single-wavelength indicators making it appropriate for conditions where there may be large changes in intracellular K⁺ (e.g. highly active synapses) or as an extracellular K⁺ sensor.
(EX 340/380 nm, EM 505 nm, Kd 4 mM ) PBFI AM is a potassium indicator that is ratiometric and UV light-excitable. This acetoxymethyl (AM) ester form is useful for noninvasive measurements of intracellular potassium levels.
While the IPG family of dyes are excellent fluorescent K⁺ indicators, the challenges of discriminating between K⁺ and Na⁺ are not trivial, and together with the often modest changes in intracellular or extracellular K⁺ results in relatively small signals compared to those observed with the Ca²⁺-sensitive fluorescent indicators. For discovering potassium channel modulators using high-throughput screening flux assay is a preferred alternative to K⁺-sensitive fluorescent indicators. Click these links to learn more about thallium indicators or potassium channel assays using thallium.
We provide our IPG family of K⁺-sensitive fluorescent indicators in membrane permeable and membrane impermeable forms.
The native forms of fluorescent potassium indicators are negatively charged and membrane impermeable. However, masking the negative charge using non-polar, ester-linked moieties (AM esters) allow the molecules to enter cells through passive diffusion. Once inside the cell, ubiquitous intracellular esterase enzymes promote rapid hydrolysis of the AM esters leaving the active, highly polar form of the indicator trapped inside the cell.
Although the AM forms of ION’s fluorescent K⁺ 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⁺ 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 out 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.
Our collection of membrane permeable and impermeable ion indicators targeting K⁺.
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| Image | Products | Excitation | Emission | Kd | Price | Quantity | Action |
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IPG-4 AM
Yellow-green fluorescent, potassium indicator, membrane permeable. Higher potassium affinity than IPG-1 and IPG-2, with improved selectivity for potassium over sodium. |
$173.00 – $391.00
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IPG-1 AM
IPG-1 AM is a yellow-green fluorescent, potassium indicator. Membrane-permeable. Lower potassium affinity than IPG-2 and IPG-4. Tailored to measure changes in potassium in environments with high potassium concentrations. |
$173.00 – $391.00
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IPG-1 TMA⁺ Salt
Yellow-green fluorescent, potassium indicator, membrane-impermeable. Lower potassium affinity (Kd = 50 mM) than IPG-2 and IPG-4. |
$334.00
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IPG-2 AM
IPG-2 is a yellow-green fluorescent, potassium indicator, membrane permeable. Lower potassium affinity than IPG-4, and higher affinity than IPG-1. |
$173.00 – $391.00
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IPG-2 TMA⁺ Salt
IPG-2 is a yellow-green fluorescent, potassium indicator. Membrane-impermeable. Lower potassium affinity than IPG-4, and higher affinity than IPG-1 |
$334.00
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IPG-4 TMA⁺ Salt
Yellow-green fluorescent, potassium indicator. Membrane-impermeable. Higher potassium affinity than IPG-1 and IPG-2, with improved selectivity for potassium over sodium. |
$334.00
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PBFI AM
PBFI AM is a ratiometric potassium indicator, membrane-permeable. |
$168.00 – $420.00
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PBFI K⁺ Salt
Ratiometric potassium indicator, membrane-impermeable. |
$380.00
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