AAT Bioquest

Protonex™ Red 670 acid

Fluorescence response of Protonex™ Red 670 in various pH solutions.
Fluorescence response of Protonex™ Red 670 in various pH solutions.
Fluorescence response of Protonex™ Red 670 in various pH solutions.
The pH-dependent absorbance spectra of Protonex™ Red 670.
The pH-dependent Emission spectra of Protonex™ Red 670.
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Physical properties
Molecular weight629.76
Spectral properties
Excitation (nm)643
Emission (nm)660
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 670 works by changing its fluorescence intensity depending on the pH of the environment. Protonex™ Red 670 is minimally fluorescent at a basic pH and maximally fluorescent at an acidic pH. When Protonex™ Red 670 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 670 to become highly fluorescent and emit red light when excited by a red laser such as a 632 nm He-Ne or 647 nm red laser. By measuring the fluorescence intensity of Protonex™ Red 670, one can monitor the activation and trafficking of receptors or antibodies in live cells. Protonex™ Red 670 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 670 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 670 can also be used to measure high-potency agonist and antagonist responses of different GPCRs in live cells, such as the activation of TRHR-1 and beta-adrenoceptor, two GPCRs that are involved in hormone regulation and cardiovascular function.


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of Protonex™ Red 670 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 mM158.791 µL793.953 µL1.588 mL7.94 mL15.879 mL
5 mM31.758 µL158.791 µL317.581 µL1.588 mL3.176 mL
10 mM15.879 µL79.395 µL158.791 µL793.953 µL1.588 mL

Molarity calculator

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Spectral properties

Excitation (nm)643
Emission (nm)660

Product Family



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