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Cal-520N™, potassium salt

Ordering information
Price ()
Catalog Number21147
Unit Size
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Additional ordering information
InternationalSee distributors
ShippingStandard overnight for United States, inquire for international
Physical properties
Dissociation constant (Kd, nM)90000
Molecular weight1004.17
Spectral properties
Excitation (nm)493
Emission (nm)515
Quantum yield0.751
Storage, safety and handling
H-phraseH303, H313, H333
Hazard symbolXN
Intended useResearch Use Only (RUO)
R-phraseR20, R21, R22
StorageFreeze (< -15 °C); Minimize light exposure


Molecular weight
Dissociation constant (Kd, nM)
Excitation (nm)
Emission (nm)
Quantum yield
Cal-520® provides a robust homogeneous fluorescence-based assay tool for detecting intracellular calcium mobilization. Cal-520® AM is a new fluorogenic calcium-sensitive dye with a significantly improved signal to noise ratio and intracellular retention compared to the existing green calcium indicators (such as Fluo-3 AM and Fluo-4 AM). Cells expressing a GPCR or calcium channel of interest that signals through calcium can be preloaded with Cal-520® AM which can cross cell membrane. Once inside the cell, the lipophilic blocking groups of Cal-520™AM are cleaved by esterases, resulting in a negatively charged fluorescent dye that stays inside cells. Its fluorescence is greatly enhanced upon binding to calcium. When cells stimulated with agonists, the receptor signals the release of intracellular calcium, which significantly increase the fluorescence of Cal-520®. The characteristics of its long wavelength, high sensitivity, and >100 times fluorescence enhancement, make Cal-520® AM an ideal indicator for the measurement of cellular calcium. The high S/N ratio and better intracellular retention make the Cal-520® calcium assay a robust tool for evaluating GPCR and calcium channel targets as well as for screening their agonists and antagonists. Cal-520® sodium or potassium salt is the hydrolyzed salt of Cal-520® AM in cells. It selectively binds to calcium ion, and has the fluorescence that is strongly dependent on calcium concentration. Compared to other Cal-520® indicators, Cal-520N™ has the lowest affinity to calcium with Kd ~ 90 uM.


Common stock solution preparation

Table 1. Volume of Water needed to reconstitute specific mass of Cal-520N™, potassium salt to given concentration. Note that volume is only for preparing stock solution. Refer to sample experimental protocol for appropriate experimental/physiological buffers.

0.1 mg0.5 mg1 mg5 mg10 mg
1 mM99.585 µL497.924 µL995.847 µL4.979 mL9.958 mL
5 mM19.917 µL99.585 µL199.169 µL995.847 µL1.992 mL
10 mM9.958 µL49.792 µL99.585 µL497.924 µL995.847 µL

Molarity calculator

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Spectral properties

Excitation (nm)493
Emission (nm)515
Quantum yield0.751

Product family

NameExcitation (nm)Emission (nm)Quantum yield
Cal-500™, potassium salt3884820.481
Cal-590™, potassium salt5745880.621
Cal-630™, potassium salt6096260.371
Cal-670™, potassium salt667680-
Cal-770™, potassium salt758783-


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