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 physically loaded with the cell-impermeant salt forms of these indicators using patch pipette, microinjection, or our Influx™ pinocytotic cell-loading reagent. The fluorescence signal from these cells is generally measured using fluorescence microscopy.

Learn more about ion indicators including calcium, potassium, pH, and membrane potential indicators ›

Calcium Indicator (Cell-Impermeant Salts) 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 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.