Calcium Indicators – Luminescent & Non-Luminescent


The aequorin complex comprises a 22 KD apoaequorin protein (APO), molecular oxygen and the luminophore coelenterazine. When three Ca2+ ions bind to this complex, coelenterazine is oxidized to coelenteramide, with a concomitant release of carbon dioxide and blue light (See figure below). The approximately third-power dependence of aequorin’s bioluminescence on Ca2+ concentration allows the measurement of Ca2+ concentrations with a broad detection range from ~0.1 µM to >100 µM. Unlike fluorescent Ca2+ indicators, Ca2+-bound aequorin can be detected without illuminating the sample, thereby eliminating interference from autofluorescence and allowing simultaneous labeling with caged probes.

AnaSpec offers coelenterazine and several synthetic coelenterazine analogs for reconstituting aequorin in cells that have been transfected with apoaequorin cDNA. In addition to native coelenterazine, we also offer a few derivatives of coelenterazine that confer different Ca2+ affinities and spectral properties on the aequorin complex. Recombinant apoaequorin reconstituted with coelenterazine hcp is reported to have the best luminescence overall, with both a high quantum yield and a fast response time. However, intracellular reconstitution of aequorin from coelenterazine analogs can be relatively slow. Aequorins containing the cp, f or h form of coelenterazine exhibit 10–20 times stronger luminescence than that of apoaequorin reconstituted with native coelenterazine. Coelenterazine cp has been used in HTS screening assay for GPCRs.

Intracellular calibration of Ca2+ indicators may be achieved either by manipulating Ca2+ levels inside cells using an ionophore or by releasing the indicator into the surrounding medium of known Ca2+ concentration via detergent lysis of cells. Along with fluorescent and luminescent Ca2+ detection reagents, AnaSpec also offers several non-luminescent compounds for measuring and manipulating intracellular and extracellular Ca2+. Amongst these, 5,5’-dimethyl BAPTA is the most powerful Ca2+ chelator, which is also available in cell-permeable AM ester form. 5,5’-difluoro BAPTA and its AM ester have been employed for optical imaging studies but are most widely used for NMR analysis of Ca2+ in live cells and tissues.

AnaSpec is pleased to showcase a wide range of reagents for luminescent Ca2+ detection and non-luminescent reagents for Ca2+ detection.

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Luminescent Calcium Indicators

Product

Size

Catalog #

Coelenterazine *UltraPure Grade*

0.25 mg

82255

Coelenterazine h *UltraPure Grade*

0.25 mg

82258

Coelenterazine f *UltraPure Grade*

0.25 mg

82257

Coelenterazine cp *UltraPure Grade*

0.25 mg

82256

Coelenterazine n *UltraPure Grade*

0.25 mg

82260

Coelenterazine hcp *UltraPure Grade*

0.25 mg

82259

Coelenterazine Sampler Kit *UltraPure Grade*

1 kit

71403


Non-luminescent calcium indicators

Product

Size

Catalog #

"BAPTA, AM *UltraPure Grade*"

25 mg

84071

"BAPTA, AM"

25 mg

84070

"5,5’-Difluoro BAPTA, AM"

25 mg

84074

"5,5’-Dimethyl BAPTA, AM"

25 mg

84076

"5,5’-Dinitro BAPTA, AM"

25 mg

84080

"BAPTA, tetrasodium salt"

100 mg

84073

"BAPTA, tetrapotassium salt"

100 mg

84072

"5,5’-Dimethyl BAPTA, tetrapotassium salt"

100 mg

84077

"5,5’-Difluoro BAPTA, tetrapotassium salt"

100 mg

84075

"EGTA, AM"

10 mg

84100

"Pluronic® F-127, 20% solution in DMSO"

10 mL

84041

Pluronic® F-127 *Cell Culture Tested *

10 g

84040

"Pluronic® F-127, 10% solution in water"

100 mL

84042

"EGTA, tetrasodium salt, 10 mM aqueous solution *UltraPure Grade*"

10 mL

84097


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