Labeled calcium indicators are molecules whose fluorescence intensity increases upon binding Ca²⁺ ions. Fluo-3 is used in flow cytometric analysis, such as experiments involving photoactivation of cage chelators, second messengers and neurotransmitters, and pharmacological screening at the cellular level, for Ca²⁺ Spatial dynamics imaging. Fluo-4 is an analogue of fluo-3 in which two chlorine substituents are replaced by fluorine, resulting in enhanced fluorescence excitation at a wavelength of 488 nm and therefore higher fluorescence signal levels. The AM ester form of this calcium indicator can be loaded onto the cells by adding the dissolved indicator directly to the culture dish containing the cultured cells. These indicators can be used in fluorescence and confocal microscopy, flow cytometric analysis, and microplate screening applications.

Calcium Indicator (AM Ester) Specifications:
• Label (Ca²⁺–conjugated form Ex/Em): Fluo-3 (506/526 nm)
• Fluorescence intensity increased after binding Ca²⁺: >100 times
• K _{bound to Ca²⁺ in buffer >d}: ∼335 nM
• After binding to Ca²⁺, the fluorescence increases and the wavelength changes slightly

Use TPEN control Heavy metal cations
In addition, BAPTA-based indicators can bind various heavy metal cations (such as Mn²⁺, Zn²⁺, Pb ⁺²), the affinity is much higher than Ca²⁺. The heavy metal selective chelator TPEN can be used to control perturbations in calcium measurements caused by these ions.

More choices of fluorescent calcium indicators
We provide a large number of Molecular Probes™ calcium indicators for use in various experimental scenarios. For more information, see Visible light excited fluorescent Ca²⁺ indicators—Chapter 19.3 section.

For UV excited Ca²⁺ indicators, protein-based Ca²⁺ indicators, Ca²⁺ indicators Conjugates of reagents and fluorescent indicators of other metal ions (i.e. Mg²⁺, Zn²⁺), please see Ca²⁺, Mg²⁺, Zn²⁺, and other metal ion indicators—Chapter 19.

For scientific research use only. Not for therapeutic or diagnostic use in humans or animals.