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Cal-520L™ maleimide

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Physical properties
Molecular weight991.78
Spectral properties
Excitation (nm)492
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
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Molecular weight
Excitation (nm)
Emission (nm)
Quantum yield
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-520L has been proven to be one of the best green fluorescent calcium indicators as a low affinity calcium indicator. Conceivably this thiol-reactive Cal-520L maleimide could be coupled to an IgG or other carrier molecules to prepare a calcium-sensitive bioconjugate for monitoring calcium change spatially for a specific target.


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of Cal-520L™ maleimide 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 mM100.829 µL504.144 µL1.008 mL5.041 mL10.083 mL
5 mM20.166 µL100.829 µL201.658 µL1.008 mL2.017 mL
10 mM10.083 µL50.414 µL100.829 µL504.144 µL1.008 mL

Molarity calculator

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Spectral properties

Excitation (nm)492
Emission (nm)515
Quantum yield0.751

Product Family

NameExcitation (nm)Emission (nm)Quantum yield
Cal-520® maleimide4925150.751



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Optogenetic stimulation of Gs-signaling in the heart with high spatio-temporal precision.
Authors: Makowka, Philipp and Bruegmann, Tobias and Dusend, Vanessa and Malan, Daniela and Beiert, Thomas and Hesse, Michael and Fleischmann, Bernd K and Sasse, Philipp
Journal: Nature communications (2019): 1281
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Red-Shifted Aequorin Variants Incorporating Non-Canonical Amino Acids: Applications in In Vivo Imaging.
Authors: Grinstead, Kristen M and Rowe, Laura and Ensor, Charles M and Joel, Smita and Daftarian, Pirouz and Dikici, Emre and Zingg, Jean-Marc and Daunert, Sylvia
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Site-specific fluorescent labeling to visualize membrane translocation of a myristoyl switch protein.
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Journal: Scientific reports (2016): 32866
Mapping Calcium-Sensitive Regions in the Neuronal Calcium Sensor GCAP2 by Site-Specific Fluorescence Labeling.
Authors: Sulmann, Stefan and Wallisch, Melanie and Scholten, Alexander and Christoffers, Jens and Koch, Karl-Wilhelm
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A Water Framework Directive-compatible metric for assessing acidification in UK and Irish rivers using diatoms.
Authors: Juggins, Steve and Kelly, Martyn and Allott, Tim and Kelly-Quinn, Mary and Monteith, Don
Journal: The Science of the total environment (2016): 671-678
Is FEV(1) an indicator of low bone mineral density in adults? The Fifth Korea National Health and Nutrition Examination Survey.
Authors: Lee, Kayoung
Journal: Journal of bone and mineral metabolism (2015): 335-41
Excited-state structural dynamics of a dual-emission calmodulin-green fluorescent protein sensor for calcium ion imaging.
Authors: Oscar, Breland G and Liu, Weimin and Zhao, Yongxin and Tang, Longteng and Wang, Yanli and Campbell, Robert E and Fang, Chong
Journal: Proceedings of the National Academy of Sciences of the United States of America (2014): 10191-6
Optogenetic control of ROS production.
Authors: Wojtovich, Andrew P and Foster, Thomas H
Journal: Redox biology (2014): 368-76
Site-specific labeling of the type 1 ryanodine receptor using biarsenical fluorophores targeted to engineered tetracysteine motifs.
Authors: Fessenden, James D and Mahalingam, Mohana
Journal: PloS one (2013): e64686