A new generation of Ca2+ indicators with greatly improved fluorescence properties

J Biol Chem. 1985 Mar 25;260(6):3440-50.


A new family of highly fluorescent indicators has been synthesized for biochemical studies of the physiological role of cytosolic free Ca2+. The compounds combine an 8-coordinate tetracarboxylate chelating site with stilbene chromophores. Incorporation of the ethylenic linkage of the stilbene into a heterocyclic ring enhances the quantum efficiency and photochemical stability of the fluorophore. Compared to their widely used predecessor, "quin2", the new dyes offer up to 30-fold brighter fluorescence, major changes in wavelength not just intensity upon Ca2+ binding, slightly lower affinities for Ca2+, slightly longer wavelengths of excitation, and considerably improved selectivity for Ca2+ over other divalent cations. These properties, particularly the wavelength sensitivity to Ca2+, should make these dyes the preferred fluorescent indicators for many intracellular applications, especially in single cells, adherent cell layers, or bulk tissues.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aminoquinolines
  • Benzofurans / chemical synthesis
  • Calcium / analysis*
  • Erythrocyte Membrane / analysis
  • Flow Cytometry
  • Fluorescent Dyes / chemical synthesis*
  • Fura-2
  • Humans
  • Hydrogen-Ion Concentration
  • Indoles / chemical synthesis
  • Magnesium / pharmacology
  • Mathematics
  • Spectrometry, Fluorescence
  • Stilbenes / chemical synthesis


  • Aminoquinolines
  • Benzofurans
  • Fluorescent Dyes
  • Indoles
  • Stilbenes
  • Magnesium
  • Quin2
  • Calcium
  • Fura-2