CalxFluor™ Series


[Calcium ion detecting probe]

590-650 nm:Red


  • Red fluorescent probe suitable for multicolor imaging with GFP, etc.
  • Sensitive detection of calcium ion.
  • Improved intracellular distribution compared to that with CaTM-2 AM enables more accurate visualization of intracellular calcium concentration changes.


We are grateful to Dr. Kenjiro Hanaoka (Graduate School of Pharmaceutical Sciences, University of Tokyo) with his support and advice for the commercialization of this product.


Available through Merck KGaA (Darmstadt, Germany ) as:
SCT021 BioTracker™ 609 Red Ca2+ AM Dye


Code No. Product Name Size Merck CAT No. Merck ( Millipore / Sigma Aldrich )
Product Name
GC507 CaTM-3 AM 40 nmol × 5 SCT021 BioTracker 609 Red Ca2+ AM Dye


  • Protocol

  • SDS

  • Product Information


    Properties of CaTM-3

    Product Name
    Target reaction Cell permeability
    Absmax (nm) FLmax (nm) Kfor Ca2+ Φ
    CaTM-3 AM Ca2+ reversible Yes (AM) 595 609 0.19 μM 0.37

    CaTM-3 AM is a red fluorescent calcium indicator. Fluorescence intensity of this fluorescent probe reversibly changes depending on Ca2+ concentration. It has red fluorescence with maximum emission at 609 nm (Excitation 590nm) and is suitable for detection of micromolar- to submicromolar-range calcium ions.

    Cell permeable CaTM-3 AM is hydrolyzed by intracellular esterases to become soluble CaTM-3 which equally distributes in the cytoplasm. This feature enables detection of intracellular calcium concentration changes with superior accuracy compared to other calcium indicators.


    Absorption and fluorescence spectra


    Absorption and fluorescence spectra of CaTM-3


    Ca2+ dose dependency 

    Fluorescence Intesity against calcium concentration

  • Cell imaging example using CaTM-3 AM


    Cell imaging example using CaTM-3 AM

    Intracellular uniform distribution

    Culture medium of HeLa cells were replaced with 3 μM of CaTM-3 AM dissolved in HBSS, and loaded the reagent at 37℃ for 30 minutes. Without additives such as Pluronic F-127, the reagent was uniformly distributed. For imaging, the reagent was excited at 590 nm and observed 610-680 nm fluorescence (left). Right panel indicates a DIC image.




    Visualization of intracellular calcium ion fluctuations induced by stimuli

    CaTM-3 (3 μM CaTM-3 AM in HBSS) loaded HeLa cells were stimulated with 1 μM of histamine to induce calcium oscillation. 3 minutes later, the cells were also stimulated with 5 μM of ionomycin to induce calcium influx to the cytoplasm.

    Data were obtained and provided by Mr. Shodai Takahashi (Graduate School of Pharmaceutical Sciences, University of Tokyo).

  • Comparison between red calcium probes


      CaTM-3 AM CaTM-2 AM Rhod-2 AM Fura-Red AM Rhod-4 AM
    Absmax  (nm) 595 597 549 435 530
    FLmax  (nm) 609 609 578 639 555
    Kd(Ca2+)  (μM) 0.19 0.2 0.57 0.4 0.53
    quantum yield 0.37 0.39 0.03 0.013  
    localization cytoplasm + nucleus cytoplasm mitochondria  

    (concentrated in mitochondria in some cells§)

    additives not required in many cases* Pluronic F-127 Pluronic F-127 Pluronic F-127 Pluronic F-127

    *Has been tested in HeLa, COS7, A549, CHO-k1, MCF-7, NIH 3T3, HEK293 cells. For the dye loading to rat hippocampal slice, addition of Pluronic F-127 and 0.005% Cremophor EL gave better results.

    §In cases of A549, NIH 3T3,COS7 cells.




  • Q What are the "AM" reagents?

    The reagents’ name end with “AM” represent acetoxy-methyl ester, those have cell permeability.

    Most of cationic compound have poor cell permeability. Some compound which cationic groups are modified with acetoxy-methyl esters are cell permeable, and the acetoxy methyls are removed by intracellular esterases to recover the original functional compound.  In addition, the original cell impermeable compound retains well inside the cell membrane.

  • Q Do I need to add Pluronic F-127 to load the probe into the cells?

    It has been reported that addition of Pluronic F-127 is not required to load CaTM-3 AM into cultured cells. For other cases, addition of Pluronic F-127 is recommended.  Refer the protocol document of each probes for the requirement and procedures. Pluronic F-127 also inhibits the aggregate formation of the probe in addition to increase cell permeability.



J. Sun, Y. Liu, X. Hao, W. Lin, W. Su, E. Chiang, M. Baudry, X. Bi (2022)
EMBO J. 41:e108119 DOI: 10.15252/embj.2021108119

F. Sasaki, M. Hayashi, Y. Mouri, S. Nakamura, T. Adachi, T. Nakashima (2019)
Biochem. Biophys. Res. Commun. 521: 806-813 DOI: 10.1016/j.bbrc.2019.10.174

N. Shakib, M. Hassan, K. Ansari, P. Karimi, Y. Rasmi (2019)
EXCLI J. 18: 229-242 DOI: 10.17179/excli2018-1947

M. Kawatani, M. Kamiya, H. Takahashi, Y. Urano (2018)
Bioorg. Med. Chem. Lett. 28: 1–5 DOI:10.1016/j.bmcl.2017.11.030

K. Hirabayashi, K. Hanaoka, T. Egawa, C. Kobayashi, S. Takahashi, T. Komatsu, T. Ueno, T. Terai, Y. Ikegaya, T. Nagano, Y. Urano (2016)
Cell Calcium 60: 256-265 DOI:10.1016/j.ceca.2016.06.002