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Protonex™ Red 780 acid

The pH-dependent absorbance spectra of Protonex™ Red 780.
The pH-dependent absorbance spectra of Protonex™ Red 780.
The pH-dependent absorbance spectra of Protonex™ Red 780.
The pH-dependent emission spectra of Protonex™ Red 780.
Ordering information
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Physical properties
Molecular weight857.18
Spectral properties
Excitation (nm)748
Emission (nm)769
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
Excitation (nm)
Emission (nm)
Protonex™ Red 780 works by changing its fluorescence intensity depending on the pH of the environment. Protonex™ Red 780 is minimally fluorescent at a basic pH and maximally fluorescent at an acidic pH. When Protonex™ Red 780 is bound to a receptor or an antibody on the cell surface, it is essentially non-fluorescent because the extracellular pH is neutral. However, when the receptor or antibody is internalized into the cell in response to a stimulus, it enters the endosomal pathway, where the pH is acidic. This causes Protonex™ Red 780 to become highly fluorescent and emit near-infrared light when excited by a red laser. By measuring the fluorescence intensity of Protonex™ Red 780, one can monitor the activation and trafficking of receptors or antibodies in live cells. Protonex™ Red 780 is especially useful in studying the activation and trafficking of G protein-coupled receptors (GPCRs), one of the most popular therapeutic drug targets. Protonex™ Red 780 can be used to label any receptor or epitope tag antibody and monitor its movement from the cell surface into acidic endosomes upon agonist stimulation. Protonex™ Red 780 might also be used to measure high-potency agonist and antagonist responses of different GPCRs in live cells.


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of Protonex™ Red 780 acid 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 mM116.662 µL583.308 µL1.167 mL5.833 mL11.666 mL
5 mM23.332 µL116.662 µL233.323 µL1.167 mL2.333 mL
10 mM11.666 µL58.331 µL116.662 µL583.308 µL1.167 mL

Molarity calculator

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Spectral properties

Excitation (nm)748
Emission (nm)769

Product Family



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