fura 2 (potassium salt)

Fura-2 is a ratiometric fluorescent calcium indicator that can be used to detect calcium in cells. [1] It is a pentacarboxylate that displays excitation maxima of 340 and 380 nm at high and low calcium concentrations, respectively, when the emission is fixed at 510 nm, enabling determination of ratiometric measurements of calcium influx in live cells.

Rhod-2 (potassium salt) is a water-soluble, red fluorescent calcium indicator. It exhibits a significant shift in fluorescence intensity upon calcium binding (ex max = 549 nm; calcium-free v. ex/em max = 552/581 nm; calcium-bound). Unlike the UV-excitable indicators fura-2 and indo-1 , there is no accompanying spectral shift.

Fura-FF AM is a cell-permeable acetoxymethyl ester of the fluorescence calcium indicator fura-FF (potassium salt) . As fura-FF AM enters cells, it is hydrolyzed by intracellular esterases to produce fura-FF. Fura-FF is a difluorinated derivative of the calcium indicator fura-2 . Unlike, fura-2, fura-FF has negligible magnesium sensitivity, thus reducing interference from this cation. Fura-FF also has a higher calcium dissociation constant than fura-2 (Kd(calcium) = 6 and 0.14 μM, respectively). However, the spectral properties of fura-FF and fura-2 are similar with fura-FF displaying excitation/emission spectra of 365/514 nm in the absence of calcium, with a shift to 339/507 nm in the presence of a high calcium concentration. Low affinity calcium dyes, including fura-FF, are preferred for studying compartments with high concentrations of calcium, such as mitochondria, or in cell systems that have relatively low calcium buffering capacities, such as neuronal dendrites and spines.