Fluo-4FF, Pentapotassium Salt, cell impermeant (Invitrogen™)

Labeled calcium indicators are molecules that exhibit an increase in fluorescence upon binding Ca²⁺. Fluo-5F, fluo-5N, and fluo-4ff are analogs of fluo-4 with lower Ca²⁺-binding affinity, making them suitable for detecting intracellular calcium levels in the 1 μM to 1 mM range that would saturate the response of fluo-3 and fluo-4. Cells may be physically loaded with the cell-impermeant salt forms of these indicators using patch pipette or microinjection or our Influx™ pinocytotic cell-loading reagent. These indicators are compatible with excitation at 488 nm by argon-ion laser sources, making them useful for confocal microscopy, flow cytometry, and microplate screening applications.

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): Fluo-4FF (494/516 nm)
• Fluorescence intensity increase upon binding Ca²⁺: >100 fold
• K_d for Ca²⁺ in buffer: ∼9.7 μM
• 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.