FluoForte® Calcium Assay Kits detect mobilisation of intracellular calcium utilising a fluorogenic calcium-binding dye optimised for superior cell-permeability and retention. The self-quenching dye undergoes an electronic change upon binding of calcium, resulting in a several order of magnitude greater fluorescence.

• Provides EC50 values comparable to Fluo-4 and Calcium 4
• Sensitive dye provides larger assay window allowing for detection of even weak signal compound responses
• Better able to detect native levels of GPCR expression in cultured cells
• Data suitable for comparison with that obtained using alternative dyes

The fluorogenic calcium-binding dye is provided to the cells as an acetoxymethyl (AM) ester, which is cell-permeable. Once inside the cells, the dye is hydrolysed by intracellular esterases, which leads to generation of a cell membrane impermeable negatively charged form. In the absence of calcium, the calcium-binding moiety portion of the probe quenches the fluorescence of the fluorophore portion of the probe by photo-induced electron transfer. Binding of calcium relieves quenching and results in a several order of magnitude increase in the fluorescence emission intensity, with no shift in wavelength. The dye is capable of binding to physiologically relevant levels of calcium and increases in intracellular calcium lead to an increased fluorescence signal, which is readily measurable.