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.[1] Fura-FF also has a higher calcium dissociation constant than fura-2 (Kd(calcium) = 6 and 0.14 µM, respectively).[1],[2]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.[3] 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.[4],[5[,[6]
Refererence:
[1]. Hyrc, K.L., Bownik, J.M., and Goldberg, M.P. Ionic selectivity of low-affinity ratiometric calcium indicators: mag-Fura-2, Fura-2FF and BTC. Cell Calcium 27(2), 75-86 (2000).
[2]. Grynkiewicz, G., Poenie, M., and Tsien, R.Y. A new generation of Ca2+ indicators with greatly improved fluorescence properties. J. Biol. Chem. 260(6), 3440-3450 (1985).
[3]. Ruggiu, A.A., Bannwarth, M., and Johnsson, K. Fura-2FF-based calcium indicator for protein labeling. Org. Biomol. Chem. 8(15), 3398-3401 (2010).
[4]. Aponte, Y., Bischofberger, J., and Jonas, P. Efficient Ca2+ buffering in fast-spiking basket cells of rat hippocampus. J.Physiol. 586(8), 2061-2075 (2008).
[5]. Canepari, M., Vogt, K., and Zecevic, D. Combining voltage and calcium imaging from neuronal dendrites. Cell.Mol.Neurobiol. 28(8), 1079-1093 (2008).
[6]. Marcu, R., Neely, C.K., Karamanlidis, G., et al. Multi-parameter measurement of the permeability transition pore opening in isolated mouse heart mitochondria. J.Vis.Exp. 67, (2012).