Use ProLong® Live Antifade Reagent for brightest fluorescent images with live cells

PBFI, Tetraammonium Salt, cell impermeant

Catalog number:  P1265MP

 Related applications:

Cell Viability, Proliferation & Function

Error loading your content!

  Catalog number
Select a plan
Unit size
Price ({{currency}}) Availability Qty
{{product.sku}} {{product.sku}} also known as {{product.formattedSku}} 
Pro add-ons

Your on-site stock

›› {{supplyCenter.scName}}({{scProduct.stockOnHand}} In stock)
›› {{supplyCenter.scName}}(Out of stock)
›› {{supplyCenter.scName}}
This item is not currently available on-site. Depending on your Supply Center settings you may be able to add the item to cart above else use the Order Non-Stocked Items' tab on the Supply Center home page.
Back to top


PBFI is a potassium-sensitive molecule used measure intracellular K+ fluxes in animal cells and in plant cells and vacuoles. Although the selectivity of PBFI for K+ is less than that of calcium indicators such as fura-2, it is sufficient for the detection of physiological concentrations of K+ in the presence of other monovalent cations. The spectral response of PBFI upon ion binding permit excitation ratio measurements, and this indicator can be used with the same optical filters and equipment used for fura-2.

Fluorescent Ion Indicators Specifications:
• Label (Ex/Em): PBFI (~340,380/500 nm)
• Lyophilized product may be dissolved in distilled water or aqueous buffer for use
• Product is typically loaded into cells by diffusion from a patch pipette for correlated fluorescence imaging and electrophysiological recording

Selectivity Considerations and Cell Loading Strategies
The Kd of PBFI for K+ is strongly dependent on whether Na+ is present, with a value of 5.1 mM in the absence of Na+ and 44 mM in solutions with a combined Na+ and K+ concentration of 135 mM (which approximates physiological ionic strength). In buffers in which the Na+ is replaced by tetramethylammonium chloride, the Kd of PBFI for K+ is 11 mM; choline chloride and N-methylglucamine are two other possible replacements for Na+ in the medium. Although PBFI is only 1.5-fold more selective for K+ than for Na+, this selectivity is often sufficient because intracellular K+ concentrations are normally about 10 times higher than Na+ concentrations.

PBFI is available as both cell-impermeant acid salt (P1265MP) and as cell-permeant acetoxymethyl (AM) esters (P1267MP). The anionic acid forms can be loaded into cells using our Influx™ pinocytic cell-loading reagent (I14402, Chelators, Calibration Buffers, Ionophores and Cell-Loading Reagents—Section 19.8), or by microinjection, patch-pipette infusion or electroporation. For AM ester loading (Loading and Calibration of Intracellular Ion Indicators—Note 19.1), addition of the Pluronic® F-127 (P3000MP, P6866, P6867) or PowerLoad™ (P10020) dispersing agents as well as relatively long incubation times—up to four hours—are typically necessary.

Find Fluorescent Indicators for Na+ and K+
We offer a number of fluorescent indicators for measuring Na+ and K+. Review Fluorescent Na+ and K+ Indicators—Section 21.1 in the Molecular Probes® Handbook for more information on these products.

For Research Use. Not for human or animal therapeutic or diagnostic use.
For Research Use Only. Not for use in diagnostic procedures.


Indicator Type: Potassium Indicator
Indicator Properties: Fluorescent Dye-Based
For Use With (Equipment): Fluorescence Microscope
Cell Permeability: Cell-Impermeant
Detection Method: Fluorescent
Product Size: 1 mg
Shipping Condition: Room Temperature

Contents & storage

Store at room temperature and protect from light.


Manuals & protocols