Labeled calcium indicators are molecules that exhibit an increase in fluorescence upon binding Ca²⁺. They have uses in many calcium signaling investigations, including measuring Ca²⁺ in cells and tissues that have high levels of autofluorescence and also for detecting Ca²⁺ release generated by photoreceptors and photoactivatable chelators. Cells may be loaded with the AM ester forms of these calcium indicators by adding the dissolved indicator directly to dishes containing cultured cells. The fluorescence signal from these cells is generally measured using fluorescence microscopy.

Calcium Indicator (AM Ester) Specifications:
• Label (Ex/Em of Ca²⁺–bound form): Rhod-2 (552/581 nm)
• Fluorescence intensity increase upon binding Ca²⁺: >100 fold
• K_d for Ca²⁺ in the absence of Mg²⁺, in buffer: ∼570 nM
• Exhibit fluorescence increase upon binding Ca²⁺ with little shift in wavelength

Using TPEN to Control Heavy Metal Cations
In addition, BAPTA-based indicators such as these bind various heavy metal cations (e.g., Mn²⁺, Zn²⁺, Pb²⁺) with substantially higher affinity than Ca²⁺. Perturbations to calcium measurements caused by presence of these ions can be controlled using the heavy metal-selective chelator TPEN.

More Choices for Fluorescent Calcium Indicators
We offer a large selection of Molecular Probes™ calcium indicators for use in various experimental scenarios, for example dextran versions for reduced leakage and compartmentalization and BAPTA conjugates for detecting high-amplitude calcium transients. For more information, review Fluorescent Ca²⁺ Indicators Excited with Visible Light—Section 19.3 in the Molecular Probes™ Handbook.

For UV-excitable Ca²⁺ indicators, protein-based Ca²⁺ indicators, conjugates of Ca²⁺ indicators, and for fluorescence-based indicators of other metal ions (i.e., Mg²⁺, Zn²⁺) review Indicators for Ca²⁺, Mg²⁺, Zn²⁺ and Other Metal Ions—Chapter 19 in the Molecular Probes™ Handbook.

For Research Use Only. Not for human or animal therapeutic or diagnostic use.