High-affinity calcium indicator, membrane impermeable. Compatible with flow cytometry, plate reader, and fluorescence microscopy assays. Also known as Fluo-2 High Affinity, Fluo-2 HA. Excitation: 490 nm | Emission: 515 nm | Kd: 290 nM | Purity: >95% Fluo-2 is a green fluorescent, calcium (Ca²⁺) indicator. Fluo-2 has higher Ca²⁺ affinity, superior cell loading and comparable spectral properties compared to Fluo-4. Offers superior sensitivity versus other Fluo analogues at lower Ca²⁺ concentrations. Fluo-2 K⁺ Salt is a membrane impermeable form of Fluo-2 that can be used in lipid membrane-free systems, in liposomes, or can be introduced into cells by electroporation, microinjection or other methods.