• K⁺ channel specific—measure ion flux in both voltage- and ligand-gated potassium channels
• Fast—perform screens in high-throughput mode with reproducible results and excellent S/N without quenching dye
• Pharmacologically relevant—known blockers show dose-dependent inhibition in a large signal window

The FluxOR™ Potassium Ion Channel Assay is an optically based, homogenous assay for high throughput screening (HTS) measurements of potassium ion channel and transporter activities. The homogenous assay is based on the permeability of potassium channels to thallium I. When potassium channels are opened by a stimulus, thallium influx from the external medium is detected with a highly sensitive indicator dye. The fluorogenic signal quantitatively reflects the activity of ion channels and transporters that are permeant to thallium, including hERG, Kir2.1, and other pharmacologically important potassium channels. Fluorescence reported in the FluxOR™ system thus becomes a surrogate indicator of activity for any ion channel or transporter that is permeable to thallium.

The FluxOR™ Potassium Ion Channel Assay enables rapid and robust high-throughput screening (HTS) of potassium channel targets in a novel equilibrium measurement, reproducibly giving IC₅₀ values that are predictive of block or modulation in lower-throughput platforms. The FluxOR™ dye is sensitive enough that low mM levels of extracellular thallium give large signals in high-throughput mode. For most applications, FluxOR™ dye is dissolved in physiological HBSS buffer for loading into cells, assisted by our proprietary Powerload™ formulation (Catalog number P10020).

The FluxOR™ Potassium Ion Channel Assay provides a concentrated thallium solution and all necessary buffers, allowing maximum target flexibility and ease of operation in a homogenous format that has been demonstrated for use with cells stably expressing hERG, as well as our BacMam-hERG delivery and expression reagent (Catalog number B10019 and B10033). Optional for use with this kit is the hERG potassium channel cDNA engineered into Invitrogen’s BacMam delivery and expression system. The combination of a bright proprietary fluorescent potassium sensor dye and the hERG potassium channel gene delivered by BacMam affords excellent assay design flexibility and superior sensitivity in detecting potassium channel activity in biologically relevant systems at physiological conditions without the need for quenchers.