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.
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.