Shop All Ion Indicators & Ionophores

NP-EGTA (o-Nitrophenyl EGTA, Tetrapotassium Salt, cell impermeant Invitrogen™

NP-caged EGTA, potassium salt is a cell-impermeant photolabile chelator that exhibits a high selectivity for Ca2+ upon UV illumination, its Kd increases from 80 nM to >1 mM. The NP-EGTA salt can be complexed with Ca2+ to generate a caged calcium complex that will rapidly deliver Ca2+ upon photolysis.

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NP-EGTA, AM (o-Nitrophenyl EGTA, AM), cell permeant Invitrogen™

Once the cell-permeant NP-caged EGTA, AM is converted to NP-EGTA by intracellular esterases, it becomes a photolabile chelator that exhibits a high selectivity for Ca2+ upon UV illumination, its Kd increases from 80 nM to >1 mM.

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Phen Green™ SK, Dipotassium Salt Invitrogen™

The green-fluorescent heavy metal indicator Phen Green™ SK, dipotassium salt can be used to detect a broad range of ions, including Cu2+, Cu+, Fe22+, Hg2+, Pb2+, Cd2+, Zn2+ and Ni2+.

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Fluo-3, AM, FluoroPure™ grade - Special Packaging 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.

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Calcium Indicator (AM Ester) Specifications:
• Label (Ex/Em of Ca2+–bound form): Fluo-3 (506/526 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.

Coelenterazine Invitrogen™

Coelenterazine and synthetic coelenterazine analogs are useful for reconstituting aequorin in cells that have been transfected with apoaequorin cDNA.

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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.

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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.

Newport Green™ DCF, Dipotassium Salt, cell impermeant Invitrogen™

The Newport Green™ DCF indicator has moderate zinc-binding affinity (Kd for Zn2+ ~1 µM) but is essentially insensitive to Ca2+ (Kd for Ca2+ >100 µM), making this a valuable probe for detecting Zn2+ influx into neurons through voltage- or glutamate-gated channels. When used alongside dyes with dual Ca2+ / Zn2+ sensitivity such as fura-2 and mag-fura-2, Newport Green™ DCF provides confirmation that changes in Zn2+ levels, and not Ca2+ or Mg2+, are being detected. The response of Newport Green™ DCF to transition metals, including Zn, Mn, Fe, Co, Cu(I), Cu(II), Ni and Cd, has been characterized.

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Newport Green™ PDX has a higher Zn2+ dissociation constant (Kd for Zn2+ ~30 µM) and a larger Zn2+-free to Zn2+-saturated fluorescence intensity increase than the Newport Green™ DCF indicators.

Fluorescent Zinc Indicators Specifications:
• Label (Ex/Em): Newport Green™ DCF (~505/535 nm)
• Kd (Zn2+) (in buffer):~1 µM
• Lyophilized product may be dissolved in distilled water or aqueous buffer for use
• Product is typically loaded into cells using 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.

Phen Green™ SK, Diacetate Invitrogen™

The green-fluorescent heavy metal indicator Phen Green™ SK, diacetate can be used to detect a broad range of ions, including Cu2+, Cu+, Fe2+, Hg2+, Pb2+, Cd2+, Zn2+ and Ni2+.

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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, FluoroPure™ grade - Special Packaging 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.

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

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.

Indo-1, Pentapotassium Salt, cell impermeant Invitrogen™

This cell-impermeant indo-1 pentapotassium salt is a UV light-excitable, ratiometric Ca2+ indicator. The emission maximum of indo-1 shifts from ~475 nm in Ca2+-free medium to ~400 nm when the dye is saturated with Ca2+. The dye is also available in the cell-permeant AM ester form—in our special packaging (I1223), in 1 mg amounts (I1203) and in 1 mM solution (I1226).

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BCEF, AM (2',7'-Bis-(2-Carboxyethyl)-5-(and-6)-Carboxyfluorescein, Acetoxymethyl Ester) Solution Invitrogen™

BCECF, AM is a cell-permeant, dual-excitation ratiometric pH indicator with a pKa of ~6.98 and is ideal for measuring changes in the cytosolic pH of most cells. Intracellular pH measurements with BCECF are made by determining the pH-dependent ratio of emission intensity (detected at 535 nm) when the dye is excited at ~490 nm versus the emission intensity when excited at its isobestic point of ~440 nm.

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Dextran, SNARF™-1, 70,000 MW, Anionic Invitrogen™

Labeled dextrans are hydrophilic polysaccharides most commonly used in microscopy studies to monitor cell division, track the movement of live cells, and to report the hydrodynamic properties of the cytoplasmic matrix. The labeled dextran is commonly introduced into the cells via microinjection.

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Dextran Specifications:

Label (Ex/Em): SNARF®-1 (563/639)
Size: 70,000 MW
Charge: Anionic
Fixable: Nonfixable

High Manufacturing Standards of Molecular Probes® Dextrans
We offer more than 50 fluorescent and biotinylated dextran conjugates in several molecular weight ranges. Dextrans are hydrophilic polysaccharides characterized by their moderate-to-high molecular weight, good water solubility, and low toxicity. They also generally exhibit low immunogeniticy. Dextrans are biologically inert due to their uncommon poly-(α-D-1,6-glucose) linkages, which render them resistant to cleavage by most endogenous cellular glycosidases.

In most cases, Molecular Probes® fluorescent dextrans are much brighter and have higher negative charge than dextrans available from other sources. Furthermore, we use rigorous methods for removing as much unconjugated dye as practical, and then assay our dextran conjugates by thin-layer chromatography to help ensure the absence of low molecular weight contaminants.

A Wide Selection of Substituents and Molecular Weights
Molecular Probes® dextrans are conjugated to biotin or a wide variety of fluorophores, including seven of our Alexa Fluor® dyes (Molecular Probes dextran conjugates–Table 14.4) and are available in these nominal molecular weights (MW): 3,000; 10,000; 40,000; 70,000; 500,000; and 2,000,000 daltons.

Dextran Net Charge and Fixability
We employ succinimidyl coupling of our dyes to the dextran molecule, which, in most cases, results in a neutral or anionic dextran. The reaction used to produce the Rhodamine Green™ and Alexa Fluor® 488 dextrans results in the final product being neutral, anionic, or cationic. The Alexa Fluor®, Cascade Blue®, lucifer yellow, fluorescein, and Oregon Green® dextrans are intrinsically anionic, whereas most of the dextrans labeled with the zwitterionic rhodamine B, tetramethylrhodamine, and Texas Red® dyes are essentially neutral. To produce more highly anionic dextrans, we have developed a proprietary procedure for adding negatively charged groups to the dextran carriers; these products are designated "polyanionic" dextrans.

Some applications require that the dextran tracer be treated with formaldehyde or glutaraldehyde for subsequent analysis. For these applications, we offer "lysine-fixable" versions of most of our dextran conjugates of fluorophores or biotin. These dextrans have covalently bound lysine residues that permit dextran tracers to be conjugated to surrounding biomolecules by aldehyde-mediated fixation for subsequent detection by immunohistochemical and ultrastructural techniques. We have also shown that all of our 10,000 MW Alexa Fluor® dextran conjugates can be fixed with aldehyde-based fixatives.

Key Applications Using Labeled Dextrans
There are a multitude of citations describing the use of labeled dextrans. Some of the most common uses include:

Neuronal tracing (anterograde and retrograde) in live cells
Cell lineage tracing in live cells
Neuroanatomical tracing
Examining intercellular communications (e.g., in gap junctions, during wound healing, and during embryonic development)
Investigating vascular permeability and blood–brain barrier integrity
Tracking endocytosis
Monitoring acidification (some dextran–dye conjugates are pH-sensitive)
Studying the hydrodynamic properties of the cytoplasmic matrix

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

BAPTA, Tetrapotassium Salt, cell impermeant Invitrogen™

The chelator BAPTA is highly selective for Ca2+ over Mg2+ and can be used to control the level of extracellular Ca2+. BAPTA is more selective for Ca2+ than EDTA and EGTA, and its metal binding is also less sensitive to pH.

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Ionomycin, Calcium Salt Invitrogen™

Ionomycin is an effective Ca2+ ionopohre that is commonly used to both modify intracellular Ca2+ concentrations and to calibrate fluorescent Ca2+ indicators when studying the regulatory properties of Ca2+ in cellular processes. Ionomycin also transports Pb2+ and some other divalent cations, as well as several lanthanide series trivalent cations, at efficiencies that are greater than or equal to those for Ca2+.

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