Shop All Ion Indicators & Ionophores

Rhod-5N, Tripotassium Salt, cell impermeant (Invitrogen™)

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.

Calcium Indicator (Cell-Impermeant Salts) Specifications:
• Label (Ex/Em of Ca2+–bound form): Rhod-5N (551/576 nm)
• Fluorescence intensity increase upon binding Ca2+: >100 fold
• Kd for Ca2+ in the absence of Mg2+, in buffer: ~320 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.

Rhod-2, Tripotassium Salt, cell impermeant (Invitrogen™)

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.

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
• Kd 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.

Calcium Green™-1 dextran, Potassium Salt, 3000 MW, Anionic (Invitrogen™)

Labeled calcium indicators are molecules that exhibit an increase in fluorescence upon binding Ca2+. They have uses in many calcium signaling investigations, including measuring intracellular Ca2+, following Ca2+ influx and release, and multiphoton excitation imaging of Ca2+ in living tissues. Cells may be physically loaded with the cell-impermeant salt forms of these dextran-conjugated indicators using patch pipette, microinjection, or our Influx pinocyte-loading reagent. The fluorescence signal from these cells is measured using fluorescence microscopy. The dextran forms of our calcium indicators show a dramatic reduction in both leakage and compartmentalization compared to the AM ester forms.

Calcium Indicator (Cell-Impermeant Salts, Dextran Conjugates) Specifications:
• Label (Ex/Em): Calcium Green™ -1 (506/531 nm)
• Fluorescence intensity increase upon binding Ca2+: ~14 fold
• Dextran size: 3,000 MW
• Exhibit fluorescence increase upon binding Ca2+ with little shift in wavelength


Spectral Characteristics of Molecular Probes® Calcium Indicators
These probes are excited by visible light, and because the energy required for excitation is low, the potential for cellular photodamage is reduced. Commonly used laser-based instruments (i.e., confocal laser scanning microscopes) are able to efficiently excite these indicators, and their emissions are in regions of the spectrum where cellular autofluorescence and scattering backgrounds are often less of a problem.

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 intended for animal or human therapeutic or diagnostic use.

Coelenterazine h (Invitrogen™)

Coelenterazine h is one of several synthetic coelenterazine analogs that confer different Ca2+ affinities and spectral properties on the aequorin complex. Like native coelenterazine, these five novel derivatives can be used to reconstitute the aequorin complex both in vivo and in vitro.

FluxOR™ Potassium Ion Channel Assay (Invitrogen™)

K+ channel specific—measure ion flux in both voltage- and ligand-gated potassium channels
Fast—perform screens in high-throughput mode with reproducible results and excellent S/N without quenching dye
Pharmacologically relevant—known blockers show dose-dependent inhibition in a large signal window

The FluxOR™ Potassium Ion Channel Assay is an optically based, homogenous assay for high throughput screening (HTS) measurements of potassium ion channel and transporter activities. The homogenous assay is based on the permeability of potassium channels to thallium I. When potassium channels are opened by a stimulus, thallium influx from the external medium is detected with a highly sensitive indicator dye. The fluorogenic signal quantitatively reflects the activity of ion channels and transporters that are permeant to thallium, including hERG, Kir2.1, and other pharmacologically important potassium channels. Fluorescence reported in the FluxOR™ system thus becomes a surrogate indicator of activity for any ion channel or transporter that is permeable to thallium.

The FluxOR™ Potassium Ion Channel Assay enables rapid and robust high-throughput screening (HTS) of potassium channel targets in a novel equilibrium measurement, reproducibly giving IC50 values that are predictive of block or modulation in lower-throughput platforms. The FluxOR™ dye is sensitive enough that low mM levels of extracellular thallium give large signals in high-throughput mode. For most applications, FluxOR™ dye is dissolved in physiological HBSS buffer for loading into cells, assisted by our proprietary Powerload™ formulation (Catalog number P10020).

The FluxOR™ Potassium Ion Channel Assay provides a concentrated thallium solution and all necessary buffers, allowing maximum target flexibility and ease of operation in a homogenous format that has been demonstrated for use with cells stably expressing hERG, as well as our BacMam-hERG delivery and expression reagent (Catalog number B10019 and B10033). Optional for use with this kit is the hERG potassium channel cDNA engineered into Invitrogen’s BacMam delivery and expression system. The combination of a bright proprietary fluorescent potassium sensor dye and the hERG potassium channel gene delivered by BacMam affords excellent assay design flexibility and superior sensitivity in detecting potassium channel activity in biologically relevant systems at physiological conditions without the need for quenchers.

Fluo-4 AM - Packaged For High-Throughput Screening (Invitrogen™)

Labeled calcium indicators are molecules that exhibit an increase in fluorescence upon binding Ca2+. Fluo-3 has been used to image the spatial dynamics of Ca2+ signaling, in flow cytometry experiments involving photoactivation of caged chelators, second messengers, and neurotransmitters, and for cell-based pharmacological screening. Fluo-4 is an analog of fluo-3 with the two chlorine substituents replaced by fluorines, which results in increased fluorescence excitation at 488 nm and consequently higher fluorescence signal levels. Cells may be loaded with the AM ester forms of these calcium indicators by adding the dissolved indicator directly to dishes containing cultured cells. These indicators are useful for fluorescence and confocal microscopy, flow cytometry, and microplate screening applications.

Calcium Indicator (AM Ester) Specifications:
• Label (Ex/Em of Ca2+–bound form): Fluo-4 (494/506 nm)
• Fluorescence intensity increase upon binding Ca2+: >100 fold
• Kd for Ca2+ in buffer: ~335 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.

Fluo-4 Direct™ Calcium Assay Kit (Invitrogen™)

The Fluo-4 Direct™ Calcium Assay Kit was formulated to provide a homogeneous fluorescent calcium assay that:
1. Easily loads into cells
2. Achieves a large assay window and
3. Suppresses background fluorescence generated from the calcium indicator in complete media with little-to-no impact on the specific cellular fluorescence

This advanced formulation allows the assay to be run in a simple “addition only" format in the presence of serum-containing media. Fluo-4 Direct™ is the third addition to the Fluo-4 family of calcium detection reagents. Fluo-4 AM and Fluo-4 NW both require media removal before assay detection, but Fluo-4 NW adds convenience by including the PowerLoad™ reagent for ease in cell loading. The Fluo-4 Direct™ Calcium Assay Kit is similar to Fluo-4 NW in that it is formulated with PowerLoad™ for ease in cell loading, but unique in that it can be used in the presence of complete culture media and will efficiently suppress background fluorescence without sacrificing the specific cellular fluorescence generated in the assay.

Fura-2, Pentasodium Salt, cell impermeant (Invitrogen™)

Fura-2, pentasodium salt is an intracellular calcium indicator that is ratiometric and UV light—excitable. This water-soluble salt form is useful for intracellular loading by microinjection, infusion from patch pipette or uptake induced by our Influx pinocytic cell-loading reagent (I-14402).

PBFI, Tetraammonium Salt, cell impermeant (Invitrogen™)

PBFI is a potassium-sensitive molecule used measure intracellular K+ fluxes in animal cells and in plant cells and vacuoles. Although the selectivity of PBFI for K+ is less than that of calcium indicators such as fura-2, it is sufficient for the detection of physiological concentrations of K+ in the presence of other monovalent cations. The spectral response of PBFI upon ion binding permit excitation ratio measurements, and this indicator can be used with the same optical filters and equipment used for fura-2.

Fluorescent Ion Indicators Specifications:
• Label (Ex/Em): PBFI (~340,380/500 nm)
• Lyophilized product may be dissolved in distilled water or aqueous buffer for use
• Product is typically loaded into cells by diffusion from a patch pipette for correlated fluorescence imaging and electrophysiological recording


Selectivity Considerations and Cell Loading Strategies
The Kd of PBFI for K+ is strongly dependent on whether Na+ is present, with a value of 5.1 mM in the absence of Na+ and 44 mM in solutions with a combined Na+ and K+ concentration of 135 mM (which approximates physiological ionic strength). In buffers in which the Na+ is replaced by tetramethylammonium chloride, the Kd of PBFI for K+ is 11 mM; choline chloride and N-methylglucamine are two other possible replacements for Na+ in the medium. Although PBFI is only 1.5-fold more selective for K+ than for Na+, this selectivity is often sufficient because intracellular K+ concentrations are normally about 10 times higher than Na+ concentrations.

PBFI is available as both cell-impermeant acid salt (P1265MP) and as cell-permeant acetoxymethyl (AM) esters (P1267MP). The anionic acid forms can be loaded into cells using our Influx™ pinocytic cell-loading reagent (I14402, Chelators, Calibration Buffers, Ionophores and Cell-Loading Reagents—Section 19.8), or by microinjection, patch-pipette infusion or electroporation. For AM ester loading (Loading and Calibration of Intracellular Ion Indicators—Note 19.1), addition of the Pluronic® F-127 (P3000MP, P6866, P6867) or PowerLoad™ (P10020) dispersing agents as well as relatively long incubation times—up to four hours—are typically necessary.

Find Fluorescent Indicators for Na+ and K+
We offer a number of fluorescent indicators for measuring Na+ and K+. Review Fluorescent Na+ and K+ Indicators—Section 21.1 in the Molecular Probes® Handbook for more information on these products.

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

5-(and-6)-Carboxy SNARF™-1, Acetoxymethyl Ester, Acetate (Invitrogen™)

Carboxy SNARF®-1, acetoxymethyl ester, acetate is a cell-permeant pH indicator that has a pKa of ~7.5 after de-esterification; thus, it is useful for measuring pH changes between pH 7 and pH 8. Carboxy-SNARF®-1 exhibits a significant pH-dependent emission shift from yellow-orange to deep red fluorescence under acidic and basic conditions, respectively. This pH dependence allows the ratio of the fluorescence intensities from the dye at two emission wavelengths - typically 580 nm and 640 nm - to be used for quantitative determinations of pH.

Fluo-5N, 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.

Calcium Indicator (Cell-Impermeant Salts) Specifications:
• Label (Ex/Em of Ca2+–bound form): Fluo-5N (494/516 nm)
• Fluorescence intensity increase upon binding Ca2+: >100 fold
• Kd for Ca2+ in buffer: ~90 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.

Fluo-5F, 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.

Calcium Indicator (Cell-Impermeant Salts) Specifications:
• Label (Ex/Em of Ca2+–bound form): Fluo-5F (494/516 nm)
• Fluorescence intensity increase upon binding Ca2+: >100 fold
• Kd for Ca2+ in buffer: ~2.3 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.

FluoZin™-3, Tetrapotassium Salt, cell impermeant (Invitrogen™)

The FluoZin™-3 indicator is a Zn2+-selective indicator with a structure that resembles fluo-4. FluoZin™-3 exhibits high Zn2+-binding affinity that is unperturbed by Ca2+ concentrations up to at least 1 µM. In addition, FluoZin™-3 exhibits a >50-fold increase in fluorescence in response to saturating levels of Zn2+. Although imaging applications of FluoZin™-3 are predominant, cell-based microplate assays and flow cytometry protocols have also been developed. FluoZin™-3 indicator is available in a cell-permeant and a cell-impermeant form.

Fluorescent Zinc Indicators Specifications:
• Label (Ex/Em): FluoZin™-3 (~494/516 nm)
• Kd (Zn2+) (in buffer): ~15 nM
• Lyophilized product may be dissolved in distilled water or aqueous buffer for use
• Product is typically loaded into cellsusing microinjection or diffusion from patch pipette


Find Fluorescent Indicators for Zinc and Other Metal Ions
We offer a number of fluorescent indicators to determine polyvalent cation concentrations inside cells, to follow metal ion transport through ion channels, to make measurements in environmental samples, and more. Review Fluorescent Indicators for Zn2+ and Other Metal Ions—Section 19.7 in the Molecular Probes® Handbook for more information on these products.

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

Fluo-4 NW Calcium Assay Kit (Invitrogen™)

Fluo-4 NW (No-Wash) Calcium Assay Kitsoffer a proprietary calcium assay formulation that requires neither a washstep nor a quencher dye. The fluo-4 NW assay achieves largerincreases in fluorescence intensity than standard fluo-3 and fluo-4assays with a wash step. Eliminating the wash step results inlower variability and higher Z´ values than the standard fluo-4 assay,while providing an easier and faster assay as well.

The fluo-4NW indicator is nonfluorescent and stable in pH 7–7.5 buffer forseveral hours, so spontaneous conversion to the Ca2+-sensitive formis not a significant source of background fluorescence. Contributionsto baseline fluorescence by the growth medium (e.g., esteraseactivity, proteins interacting with receptors of interest, or phenolred) are eliminated by removing the medium prior to adding theindicator dye to the wells.

Another source of potential fluorescenceoutside the cells is extrusion of the indicator out of the cell by organicanion transporters. Probenecid is commonly used to inhibitthis transport and reduce the baseline signal. We have synthesizeda proprietary water-soluble probenecid, which is supplied with theFluo-4 NW Calcium Assay Kits. This form of probenecid has theadvantages of being easy to dissolve in buffer and safer to use thanthe free acid, which requires caustic 1 M NaOH to dissolve. TheFluo-4 NW Calcium Assay Kits are designed for microplates andHTS, and the assay can be performed on adherent as well as nonadherentcells.

Fluo-4 AM is a fluorescent Ca+2 indicator that is widely usedfor in-cell measurement of agonist-stimulated and antagonist inhibitedcalcium signaling in high-throughput screening (HTS)applications. Its visible wavelength excitation (compatible withargon-ion laser sources), high sensitivity, and large fluorescenceincrease upon binding Ca2+ has made it the indicator of choicefor characterizing G-protein–coupled receptor (GPCR) pharmacologyand function. These properties have made fluo-4 AMattractive not only for microplate screening applications but formicroscopy and flow cytometry as well.

SNARF™-4F 5-(and-6)-Carboxylic Acid (Invitrogen™)

The cell-impermeant ratiometric pH indicator SNARF®-4F 5-(and-6)-carboxylic acid (pKa of ~6.4) exhibits a significant pH-dependent emission shift from yellow-orange to deep red fluorescence under acidic and basic conditions, respectively. This pH dependence allows the ratio of the fluorescence intensities from the dye at two emission wavelengths - typically 580 nm and 640 nm - to be used for quantitative determinations of pH.