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Cal-500™ AM
Calcium measurement is critical for numerous biological investigations. Fluorescent probes that show spectral responses upon binding calcium have enabled researchers to investigate changes in intracellular free calcium concentrations by using fluorescence microscopy, flow cytometry, fluorescence spectroscopy and fluorescence microplate readers. Cal-500™ is an UV-excitable calcium indicator with maximum emission at ~500 nm. It has a Stokes Shift larger than 100 nm. It can also be well excited with the 405 nm violet laser with a moderate calcium affinity of Kd ~303 nM. In CHO and HEK cells Cal-500™ AM has great cellular calcium response. The excitation spectra of Cal-500 is well separated from those of FITC, Alexa Fluor® 488 and GFP, making it an ideal calcium probe for multiplexing intracellular assays with GFP cell lines, FITC/Alexa Fluor® 488 labeled antibodies or other red fluorescent probes.
Response of endogenous P2Y receptor to ATP in CHO-K1 cells. CHO-K1 cells were seeded overnight at 40,000 cells per 100 µL per well in a 96-well black wall/clear bottom costar plate. 100 µL of Cal-500™ AM in HHBS with probenecid were added into the wells, and the cells were incubated at 37 °C for 60 min. The dye-loading medium was replaced with 200 µL HHBS. Images were taken before and after adding 50 µL of 10 µM ATP via a fluorescence microscope (Keyence) using 405 nm and 465 nm long pass filters.
Response of endogenous P2Y receptor to ATP in CHO-K1 cells. CHO-K1 cells were seeded overnight at 40,000 cells per 100 µL per well in a 96-well black wall/clear bottom costar plate. 100 µL of Cal-500™ AM in HHBS with probenecid were added into the wells, and the cells were incubated at 37 °C for 60 min. The dye-loading medium was replaced with 200 µL HHBS. Images were taken before and after adding 50 µL of 10 µM ATP via a fluorescence microscope (Keyence) using 405 nm and 465 nm long pass filters.
protocol
Protocol
sds
SDS
COA
CatalogSize
Price
Quantity
2041210x50 ug
Price
 
Physical properties
Dissociation constant (Kd, nM)303
Molecular weight1019.92
SolventDMSO
Spectral properties
Excitation (nm)388
Emission (nm)482
Quantum yield
0.48
1
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
UNSPSC12352200
Instrument settings
Fluorescence microscope
ExcitationDAPI
EmissionDAPI
Recommended plateBlack wall/clear bottom
Fluorescence microplate reader
Excitation400
Emission500
Cutoff470
Recommended plateBlack wall/clear bottom
Instrument specification(s)Bottom read mode/Programmable liquid handling
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Page updated on October 12, 2025