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Cal-520™ Calcium Indicators
Cal-520™ provides the most 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 background ratio and intracellular retention compared to the existing green calcium indicators (such as Fluo-3 AM and Fluo-4 AM). The higher signal/background 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. Our preliminary in-house research indicated that Cal-520™ AM can be readily loaded to a guinea pig heart and stays there for a few hours in the absence of probenecid. The calcium signal can be readily monitored with Cal-520™ AM while it is difficult to observe the calcium signal under the same conditions with other green calcium dyes, such as Fluo-3 AM and Fluo-4 AM.
Key Features of Cal-520™ AM:
- Better Intracellular Retention, Cal-520™ AM is better retained in live cells than Fluo-3 AM and Fluo-4 AM.
- Higher Sensitivity, Cal-520™ AM has much higher signal/background ratio than Fluo-3 AM and Fluo-4 AM in cells.
- Convenient, Cal-520™ AM has almost identical spectra to those of Fluo-4 AM.
Fig. 1
Left: ATP-stimulated calcium responses of endogenous P2Y receptor in CHO-K1 cells incubated with Cal-520™ AM (red curve, Cat# 21131), or Fluo-4 AM (blue curve) respectively with probenecid under the same conditions. CHO-K1 cells were seeded overnight at 50,000 cells/100 µL/well in a Costar 96-well black wall/clear bottom plate. 100 µL of 5 µM Fluo-4 AM or Cal-520™ AM in HHBS with 2.5 mm probenecid was added into the cells, and the cells were incubated at 37 °C for 2 hours. ATP (50 µL/well) was added using FlexSation® to achieve the final indicated concentrations. Right: ATP-stimulated calcium responses of endogenous P2Y receptors in CHO-K1 cells incubated with Cal-520™ AM (red curve, Cat# 21131), or Fluo-4 AM (blue curve) respectively, without probenecid under the same conditions. CHO-K1 cells were seeded overnight at 50,000 cells/100 µL/well in a Costar 96-well black wall/clear bottom plate. 100 µL of 5 µM Fluo-4 AM or Cal-520™ AM in HHBS was added into the cells, and the cells were incubated at 37 °C for 2 hours. ATP (50 µL/well) was added using FlexSation® to achieve the final indicated concentrations.
Document: 03.0071.150501r1
Last updated Fri Oct 03 2025
Cal-520™ Calcium Indicators