$173.00
Sodium indicators, which exhibit an increase in fluorescence upon binding Na⁺ , can be used to measure the activity of sodium channels and transporters.
In most cells at rest, cytoplasmic Na⁺ concentrations are ~5 mM while K⁺ concentrations are above 100 mM. Conversely, extracellular Na⁺ concentrations are typically >100 mM while K⁺ concentrations are in the 3-5 mM range. Therefore, an effective Na⁺ sensor needs to be able to discriminate between K⁺, Na⁺ and other common physiological cations while possessing an appropriate Na⁺ affinity to detect physiologically relevant changes in Na⁺ concentrations.
ION Natrium Green-2 (ING-2), formerly known as Asante Natrium Green (ANG-2), is a small, synthetic fluorochrome fused with a Na⁺-binding moiety. Under conditions where Na⁺ is not bound, the fluorescence of the sensor is significantly quenched. When Na⁺ is bound, the quenching is relieved, and the fluorescence of the sensor dramatically increases.
ING-2 (EX 525 nm, EM 545 nm, Kd 20 mM) is the best-in-class fluorescent Na⁺ sensor replacing previous Na⁺ indicators such as SBFI and CoroNa Green. Its affinity for Na⁺ is well suited to respond to changes in intracellular Na⁺ concentrations resulting from activation of plasma membrane Na⁺ permeable channels and Na⁺ transporters. It is compatible with a wide variety of detectors including fluorescent microscopes, plate readers, and flow cytometers using common filter sets like sets (e.g. YFP and FITC) as well as multiphoton approaches. ING-2 has also proven useful for high-throughput screening (HTS).
SBFI is a UV-excitable, ratiometric green indicator for intracellular sodium (Na⁺) measurements. Ex/Em: 340/505 nm can be used to measure Na⁺-bound SBFI, and Ex/Em: 380/505 nm can be used to detect Na⁺-free SBFI. It is ~18X more selective for Na⁺ over K⁺. Ratiometry is optimal for imaging applications where quantification of intracellular Na⁺ concentrations is desired, and reduces effects of photobleaching, heterogenous dye loading, and variable cell morphology.
We provide ING-2 in membrane permeable and membrane impermeable forms, as well as in our Brilliant Sodium Assays. SBFI and ING-1 are also provided as AM esters and salts.
The native forms of the Na⁺-sensitive fluorescent 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, Na⁺ 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 Na⁺ and Tl⁺ indicators into cells, it is highly recommended.
Another factor that can affect cell loading and intracellular localization is the presence of anion transport proteins in both plasma and intracellular membranes. 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 sodium indicators nearly impossible. Fortunately, probenecid, an organic anion transport inhibitor can be an effective means of inhibiting the transporters, improving cytoplasmic localization and indicator retention. ION offers a convenient, 100X probenecid solution that may be used in conjunction with our Na⁺ sensitive fluorescent indicators. While probenecid is generally well-tolerated over the time course of typical experiments effects on the activity of TRP channels has been reported.
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| Image | Products | Excitation | Emission | Kd | Price | Quantity | Action |
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ING-2 AM
ING-2 AM is a yellow-green fluorescent, sodium indicator. Membrane-permeable. Higher sodium affinity than ING-1. Suitable for high throughput screening of sodium channels and transporters. |
$173.00 – $391.00
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ING-2 TMA⁺ Salt
Yellow-green fluorescent sodium indicator, membrane-impermeable. Higher sodium affinity than ING-1. Suitable for high throughput screening of sodium channels and transporters. |
$334.00
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ING-1 AM
ING-1 AM is a yellow-green fluorescent, sodium indicator. Membrane-permeable. Lower sodium affinity than ING-2. |
$173.00 – $391.00
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SBFI AM
SBFI AM is a ratiometric sodium indicator. UV-excitable. Membrane-permeable. |
$166.00 – $414.00
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SBFI K⁺ Salt
Ratiometric sodium indicator, membrane-impermeable. |
$414.00
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