Calcium measurement is critical for numerous biological investigations. Fluorescent probes that show spectral responses upon binding Ca2+ have enabled researchers to investigate changes in intracellular free Ca2+ concentrations by using fluorescence microscopy, flow cytometry, fluorescence spectroscopy and fluorescence microplate readers. Fluo-3 and Fluo-4 are most commonly used among the visible light-excitable calcium indicators. However, Fluo-3 AM and Fluo-4 AM are only moderately fluorescent in live cells upon esterase hydrolysis, and require harsh cell loading conditions to maximize their cellular calcium responses. Fluo-8 dyes are developed to improve cell loading and calcium response while maintaining the convenient Fluo-3 and Fluo-4 spectral wavelength of maximum excitation @ ~490 nm and maximum emission @ ~520 nm. Fluo-8 AM only requires room temperature while Fluo-3 AM and Fluo-4 AM require 37   C cell loading. In addition, Fluo-8 is 2 times brighter than Fluo-4 AM, and 4 times brighter than Fluo-3 AM. AAT Bioquest offers a set of our outstanding Fluo-8 reagents with different calcium binding affinities (Fluo-8: Kd = 389 nM; Fluo-8H: Kd = 232 nM; Fluo-8L: Kd = 1.86 M; Fluo-8FF: Kd = 10 M). We also offer versatile packing sizes to meet your special needs, e.g., 1 mg; 10x50 g; 20x50 g; HTS packages with no additional packaging charge. ***Patents Pending***