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PRO-TAO-3 [equivalent to TO-PRO-3]

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Physical properties
Molecular weight671.42
Spectral properties
Extinction coefficient (cm -1 M -1)102000
Excitation (nm)642
Emission (nm)657
Quantum yield0.111
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


Molecular weight
Extinction coefficient (cm -1 M -1)
Excitation (nm)
Emission (nm)
Quantum yield
PRO-TAO-3 is the same molecule to TO-PRO®-3 stain. TO-PRO®-3 and the other monomeric cyanine stains have wide applicability due to their low background and bright fluorescence. It is a carbocyanine monomer nucleic acid stain that can be well excited by a red laser at 633 nm or 647 nm with far-red fluorescence similar to Cy®5 dyes. It is useful as a nuclear counterstain and dead cell indicator. It is selective for detecting dsDNA (double-stranded nucleic acids). The cell-impermeable PRO-TTO-3 is widely used for flow cytometry and fluorescence microscopy as a long-wavelength fluorescence well separated from green and red fluorophores in multicolor applications. TO-PRO® is the trademark of ThermoFisher Scientific.


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of PRO-TAO-3 [equivalent to TO-PRO-3] 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 mM148.938 µL744.69 µL1.489 mL7.447 mL14.894 mL
5 mM29.788 µL148.938 µL297.876 µL1.489 mL2.979 mL
10 mM14.894 µL74.469 µL148.938 µL744.69 µL1.489 mL

Molarity calculator

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Spectral properties

Extinction coefficient (cm -1 M -1)102000
Excitation (nm)642
Emission (nm)657
Quantum yield0.111

Product Family

NameExcitation (nm)Emission (nm)Extinction coefficient (cm -1 M -1)Quantum yield
TWO-PRO™ 3 [equivalent to TO-PRO®-3] *5 mM DMSO Solution* *CAS 157199-63-8*64265710200010.111



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