Name: Cal-520®, AM
Brand: AAT Bioquest
SKU: 21130
Availability: InStock

Cal-520®, AM

Cal-520® AM is a cell-permeable calcium indicator with enhanced brightness and improved cellular retention compared to traditional indicators, providing robust fluorescence-based detection of intracellular calcium mobilization in live cells.

Significantly improved signal to noise (S/N) ratio
Excellent intracellular rentention, even without probenecid
Replaces outdated calcium indicators such as Fluo-3 and Fluo-4

ATP-stimulated calcium responses of endogenous P2Y receptor in CHO-K1 cells incubated with Cal-520™ AM (red curve), or Fluo-4 AM (blue curve) respectively with (left) or without probenecid (right) under the same conditions. CHO-K1 cells were seeded overnight at 50,000 cells per 100 µL per well in a Costar black wall/clear bottom 96-well plate. 100 µL of 5 µM Fluo-4 AM or Cal 520™ AM in HHBS (with or without probenecid) was added into the cells, and the cells were incubated at 37 °C for 1 hour. ATP (50 μL/well) was added using FlexSation to achieve the final indicated concentrations.

Protocol

Catalog	Size	Price	Quantity
21130	10x50 ug	Price
21131	1 mg	Price

Overview

Mechanism and Principle

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®.

Application

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.

Calculators

Common stock solution preparation

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

	0.1 mg	0.5 mg	1 mg	5 mg	10 mg
1 mM	90.666 µL	453.33 µL	906.659 µL	4.533 mL	9.067 mL
5 mM	18.133 µL	90.666 µL	181.332 µL	906.659 µL	1.813 mL
10 mM	9.067 µL	45.333 µL	90.666 µL	453.33 µL	906.659 µL

Molarity calculator

Enter any two values (mass, volume, concentration) to calculate the third.

Mass (Calculate)		Molecular weight		Volume (Calculate)		Concentration (Calculate)		Moles
mg	÷	1102.95 g/mol	=	mL	x	mM	=	mmol

Citations

View all 636 citations: Citation Explorer

Micro-nano microbial fuel cell-driven bioelectrochemical tumor therapy

Authors:

Li, Ruiyan and Kang, Yong and Ran, Nana and Niu, Gaoli and Fan, Yueyue and Zhang, Yijing and Ye, Jiamin and Yuan, Xue and Shi, Jiacheng and Ding, Mengbin and others,

Journal:

Nature Communications (2025): 8989

Optoelectronic Interfaces for Nongenetic Modulation of Excitable Tissues

Authors:

Wang, Qi and Li, Jinghua

Journal:

Small Methods (2025): e01371

Enteropathogenic E. coli-mediated Fast and Coordinated Ca2+ responses regulate NF-$\kappa$B activation

Authors:

TRAN VAN NHIEU, Guy and GUO, Fangrui and GUEVARA, Roberto and OUSSAEIDINE, Linda and DUPONT, Genevi{\`e}ve and COMBETTES, Laurent

Journal:

bioRxiv (2025): 2025--08

BS31 Functional characterisation of human cardiac pericytes using neural stimulation and Ca2+ imaging in vitro

Authors:

Mistry, Adam and Pravica, Nika B and Avolio, Elisa and Mastitskaya, Svetlana and James, Andrew F

An Activated Gasdermin Mimicking Polymer for Antitumor Immunity

Authors:

Li, Junjun and Mu, Yongli and Chen, Yinqi and Zhang, Xuanhao and Wang, Yechun and Wang, Jiafeng and Ying, Jiajia and Yang, Hang and Zhou, Xuefei and Du, Yushen and others,

Journal:

ACS nano (2025)

References

View all 72 references: Citation Explorer

Measurement and simulation of myoplasmic calcium transients in mouse slow-twitch muscle fibres

Authors:

Hollingworth S, Kim MM, Baylor SM.

Journal:

J Physiol (2012): 575

Mononucleated and binucleated cardiomyocytes in left atrium and pulmonary vein have different electrical activity and calcium dynamics

Authors:

Huang CF, Chen YC, Yeh HI, Chen SA.

Journal:

Prog Biophys Mol Biol (2012): 64

Changes in serum levels of HBV DNA and alanine aminotransferase determine risk for hepatocellular carcinoma

Authors:

Chen CF, Lee WC, Yang HI, Chang HC, Jen CL, Iloeje UH, Su J, Hsiao CK, Wang LY, You SL, Lu SN, Chen CJ.

Journal:

Gastroenterology (2011): 1240

A near-infrared fluorescent calcium probe: a new tool for intracellular multicolour Ca2+ imaging

Authors:

Matsui A, Umezawa K, Shindo Y, Fujii T, Citterio D, Oka K, Suzuki K.

Journal:

Chem Commun (Camb) (2011): 10407

Application of fluorescent indicators to analyse intracellular calcium and morphology in filamentous fungi

Authors:

Nair R, Raina S, Keshavarz T, Kerrigan MJ.

Journal:

Fungal Biol (2011): 326

Physical properties

Dissociation constant (K_d, nM)	320
Molecular weight	1102.95
Solvent	DMSO

Spectral properties

Excitation (nm)	492
Emission (nm)	515
Quantum yield	0.75 ¹

Storage, safety and handling

H-phrase	H303, H313, H333
Hazard symbol	XN
Intended use	Research Use Only (RUO)
R-phrase	R20, R21, R22
Storage	Freeze (< -15 °C); Minimize light exposure
UNSPSC	12352200

Instrument settings

Fluorescence microscope
Excitation	FITC
Emission	FITC
Recommended plate	Black wall/clear bottom

Fluorescence microplate reader
Excitation	490
Emission	525
Cutoff	515
Recommended plate	Black wall/clear bottom
Instrument specification(s)	Bottom read mode/Programmable liquid handling

Documents

Protocol
Safety Data Sheet (Catalog 21130)
Safety Data Sheet (Catalog 21131)
Certificate of Analysis
Flyer: Calcium Indicators
Brochure: Physiological Probes & Assay Kits
Brochure: Calcium Detection Probes & Assay Kits

Telephone
Fax
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Page updated on October 29, 2025