AAT Bioquest

Protonex™ Red 670, NHS ester

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Physical properties
Molecular weight827.02
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 NHS ester is an excellent building block for developing a target-specific conjugate that can be used for monitoring a pH-sensitive biological event. Protonex™ Red 670 dye 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.


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of Protonex™ Red 670, NHS ester 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 mM120.916 µL604.58 µL1.209 mL6.046 mL12.092 mL
5 mM24.183 µL120.916 µL241.832 µL1.209 mL2.418 mL
10 mM12.092 µL60.458 µL120.916 µL604.58 µL1.209 mL

Molarity calculator

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Spectral properties

Excitation (nm)643
Emission (nm)660

Product Family

NameExcitation (nm)Emission (nm)
Protonex™ Red 780, NHS ester748769